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#18746 - 10/27/11 01:53 PM Re: Using DU to Clone Lion to a APM firewire drive [Re: Hal Itosis]
alternaut Offline

Moderator

Registered: 08/04/09
To dispel any doubt, my previous post was not intended to argue against your position, but just a statement of practice. FWIW, I sure do recall those florfed clones, and I have this dark-green suspicion (no hard supporting figures here either) that many—if not most—of those problems had to do with cloning while continuing to work and/or with hardware glitches.

In conclusion, I have no argument whatsoever with your backup approach, but I haven't had occasion (yet) to follow it either. tongue
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#18747 - 10/27/11 10:00 PM Re: Using DU to Clone Lion to a APM firewire drive [Re: Hal Itosis]
RHV Offline


Registered: 09/19/09
Loc: Winnipeg, Kenora, Palm Springs...
Nice Try Hal.

You are way, way off the topic. I was surprised by that. You are no dummy.

But you were addressing the question whether or not clones are reliable. I was not -- though I said, as a personal comment, that my clones were reliable after testing for a day even when they were done from the boot volume.

But I was addressing in my post a different issue. And surely that issue was apparent.

I was addressing the issue as to whether clones done from the boot volume are less reliable than those done from another volume. Ganbustein thinks that clones done from the boot volume are less reliable. I challenged that on the basis of no properly acquired data provided by Ganbustein.

And you did not deal with that issue in your reply to me -- but dealt with the issue as to whether clones in general are reliable. On that one, I suspect that proper data will show that they are.

And yes; I've been on Macfixit since about 2000 and on OSX Hints forums since about 2001 -- if that matters to the issue dealt with in my post. I bought my first Mac in 1984 -- a Mac that had all the guys (some gals?) sign the interior backside panel of the computer. I think that I paid $5,000 for the computer, an external drive, and the printer.




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#18748 - 10/28/11 06:28 AM Re: Using DU to Clone Lion to a APM firewire drive [Re: RHV]
Hal Itosis Offline


Registered: 09/03/09
Loc: 10.6.8 (build 10K549)
Originally Posted By: RHV
Nice Try Hal.

You are way, way off the topic. I was surprised by that. You are no dummy.

But you were addressing the question whether or not clones are reliable. I was not -- though I said, as a personal comment, that my clones were reliable after testing for a day even when they were done from the boot volume.

But I was addressing in my post a different issue. And surely that issue was apparent.

I was addressing the issue as to whether clones done from the boot volume are less reliable than those done from another volume. Ganbustein thinks that clones done from the boot volume are less reliable. I challenged that on the basis of no properly acquired data provided by Ganbustein.

And you did not deal with that issue in your reply to me -- but dealt with the issue as to whether clones in general are reliable. On that one, I suspect that proper data will show that they are.

And yes; I've been on Macfixit since about 2000 and on OSX Hints forums since about 2001 -- if that matters to the issue dealt with in my post. I bought my first Mac in 1984 -- a Mac that had all the guys (some gals?) sign the interior backside panel of the computer. I think that I paid $5,000 for the computer, an external drive, and the printer.

How would you know if my answer addressed your question or not? Perhaps clones done that way are more susceptible to the phenomena which i discussed. No one ever found out for sure what the exact mechanism was... that was my point.

Anyway... it should be self-evident that cloning an OS which is actively running (with open files, etc.) would indubitably be more susceptible to any sort of quirk, than cloning a totally inactive OS from some other volume. That's just basic logic, and certainly nothing over which to get all worked up or demand detailed analysis about.

Perhaps CCC and SD have managed to solve the matter over the years, and found the exact file(s) to exclude/tweak/whatever... idunno. But some special step was probably needed to overcome the potential for such problems... which don't present themselves when cloning an inactive OS volume. If you're that interested, try asking in the forums over at bombich.com or shirt-pocket.com maybe.


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#18749 - 10/28/11 08:33 AM Re: Using DU to Clone Lion to a APM firewire drive [Re: RHV]
alternaut Offline

Moderator

Registered: 08/04/09
It's funny: I was thinking about a reply to your post when I noticed Hal's response (I read both on my iPod, but don't like to use that for more than a brief reply). My take on Hal's posts was that his reservations were about (making) clones of a running boot volume, not so much about clones in general. After rereading those post I still think that way, and the funny thing of course is that neither you nor Hal don't quite seem to. Shows you how easy it can be to misunderstand each other.

And that's another reason for my post: although I understand how one might view this otherwise, I took Hal's comment about not having seen you at MFIF at face value, and not as the slight you may have taken it for.

As to your original Mac, I bought one too in early '84, but I recall paying about 3K (US) for it including Apple printer and (later) external floppy drive. Your 5K must have been Canadian, right?
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#18754 - 10/28/11 01:46 PM Re: Using DU to Clone Lion to a APM firewire drive [Re: alternaut]
Hal Itosis Offline


Registered: 09/03/09
Loc: 10.6.8 (build 10K549)
Originally Posted By: alternaut
Your 5K must have been Canadian, right?

In 1989, even with an educational discount, the price for a Mac IIci with Portrait Grayscale monitor ran up to 5K (at least in Boston it did). They sit in storage now, as i don't have the heart to toss them in a scrap heap.

[and yes, the MFI forums reference was strictly about one having seen the numerous clone issue threads.]


Edited by Hal Itosis (10/28/11 01:51 PM)

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#18772 - 10/29/11 03:09 PM Re: Using DU to Clone Lion to a APM firewire drive [Re: RHV]
ganbustein Offline


Registered: 08/04/09
Originally Posted By: RHV
Well, from the point of view of time, cloning by booting from a different volume is not the easiest way. The easiest way is to clone from the boot volume.

I wasn't talking about the easiest way to do it (which, by the way, is to not do it al all), but rather the easiest way to do it reliably.

The first rule of optimization is: any optimization must be correct. No one will be impressed if you get the wrong answer faster.

Originally Posted By: RHV
And, in my eight or so years of experience using Mac OS X's DU for cloning, up to Snow Leopard and now with Lion using CCC, cloning from the boot volume works just peachy fine. And I never bother to close down the internet connection either. Unlike Tacit, I don't bother to close down all the apps I've just been using. So what if Text Edit is open and so is Safari? Makes no difference.

There was a formative moment in my earlier career. I was working as a Tech Rep for Burroughs Corporation, and one of my fellow Tech Reps told a customer, a heavy user of Burroughs' reader/sorter machines (used to sort checks based on their MICR coding) "Don't worry about that. There's only a one-in-a-million chance that that would ever happen." The customer replied "At Bank of America, one in a million happens fifty times a day."

That made a big impression on me. It doesn't matter how unlikely something is. If it can happen, it will. Testing once or twice or even a million times isn't good enough. You have to design your algorithms and procedures to make errors impossible, not merely unlikely.

If you tell me you've been making clones of running systems for 8 years (and also tell me you test each one by booting from it for a day), I figure you've only tested it about 400 times (once a week at most), and "running with it for a day" hardly comes close to a thorough test. I am not impressed.

Backing up any digital file while it's being updated is a well-known danger. Look up the "readers and writers problem" in any text on databases, but don't think for a minute that the problem only affects "database applications". Or look up "readers and writers problem" in any text on concurrent programming. Even something as simple as incrementing a number in memory can be problematic on a machine with multiple cores.

This is not a hypothetical risk. It's common, especially among neophytes who think "I tested it and it works" means that it will always work. Experienced programmers know better. If you want to take a digital snapshot of something, you have to freeze it for the duration of the snapshot. One of the reasons we prefer digital copies over analog copies is that successive analog copies get blurrier and blurrier, but digits don't blur. Trouble is, when you make a digital copy of a changing file, you eventually discover that digits don't blur, they break.

Edsgar Dijkstra, one of the pioneers of Computer Science, famously said "Testing can only reveal the presence of bugs, never their absence." The tests you've made fall under that heading. The fact that you haven't found a bug yet doesn't mean you won't find one tomorrow, or even that there weren't undiscovered bugs in the past.

My data is more valuable to me than that. I want to know that my backups are good. Hoping isn't good enough.

Originally Posted By: RHV
After doing a clone, I always test it by booting from it for a test day. Never found a problem.
A day? How thorough a test can you do in a day? I've got 1.6 million files on my boot volume. How could I ever test all of them in a single day?

And you think booting off the clone (and not getting any real work done during that day, because you'd be updating the wrong disk) is easier than what I do, which only costs me about an hour of down time?

Originally Posted By: RHV
I'll happily and thankfully bow to Ganbustein if he can produce a good sized sample of competent Mac users who have had trouble cloning from the boot volume. Even better, if that sample was statistically significant. (Most samples aren't.)

Hal has already pointed out where you can find some, and most users who have problems won't say "I cloned a running system and this is what went wrong." Usually, if they say anything at all, they'll say "I'm having a problem with X", and if we're lucky we'll eventually pull out of them the oh-by-the-way comment about how they restored from such a backup two years ago, and it turns out the problem has been lurking in their system all that time. But usually, even if the backup is bad, they don't know, because most users never test their backups, and the few that do make only a few spot-checks, usually limited to "It boots, so it must be good."

I also talked at length about all the files that Retrospect found changing during each backup. Many of those were files I really wanted reliable backups of. And there's also the problem that many applications cache data in RAM, and don't bother keeping their disk files consistent until the program quits. Many of those applications are actually "system processes" that run in the background, so you don't even know you're running them, yet cloning their disk files will give you inconsistent data.

I have at times had to recover from backup. Most of those times, the problem was because the disk catalog got corrupted. For that reason, I don't trust anything that copies the catalog itself. In particular, I don't trust a sector-level copy, like with DU. Even if I'm not booted from the volume. If I had used a sector level copy in those situations, my "backup" would be just as bad as the original.

You're looking at it wrong. It's not a question of "what are the odds?" It's a question of "what's reliable?" For bugs, even a single occurrence is "statistically significant", especially if that occurrence happens to me.

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#18774 - 10/29/11 07:20 PM Re: Using DU to Clone Lion to a APM firewire drive [Re: ganbustein]
macnerd10 Offline


Registered: 08/04/09
Loc: Los Angeles, CA
To make a long story short, my understanding is that both you and Hal are advocating cloning of a "resting" volume. Does this mean that you need to have three drives: the active volume that has the cloning software running, the inactive source (also bootable) and the target drive? I kind of doubt that this is a standard setup unless one has a desktop with two drives and an external. Are you guys doing it that way?

P.S. I started a thread at the SuperDuper home about this issue. Will report when David or someone else answers.


Edited by macnerd10 (10/29/11 07:21 PM)
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3.1 GHz 13" MacBook Pro 2015, 8 GB RAM, OS 10.11.2, Office 2011, TimeWarner Cable
2.8 GHz Xeon Mac Pro 2010, 16 GB RAM, OS 10.11.2, Office 2011, LAN

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#18775 - 10/29/11 08:10 PM Re: Using DU to Clone Lion to a APM firewire drive [Re: macnerd10]
dkmarsh Offline

Moderator

Registered: 08/04/09

Why would you need three drives? It's entirely possible to have three volumes on a single drive, and to be booted from volume B while cloning volume A to volume C.

Obviously, since cloning from one volume to another on the same drive does you no good if the drive itself fails, in practical terms you do need a second drive—typically, an external—but a second bootable volume on either the internal or external drive is sufficient to avoid cloning a booted volume.
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#18776 - 10/29/11 11:07 PM Re: Using DU to Clone Lion to a APM firewire drive [Re: dkmarsh]
ryck Online


Registered: 08/04/09
Loc: Okanagan Valley
Originally Posted By: dkmarsh
....but a second bootable volume on either the internal or external drive is sufficient to avoid cloning a booted volume.

I was wondering the same thing as Alex. (Everyone in class is always so happy when some other kid is willing to raise his arm first) So, to be clear, this is what I now understand.

I would repartition my backup drive into two volumes. In one partition I install a system and Super Duper. The other partition would be reserved for my Clone.

When I make my clone I reboot from the drive that has the system and Super Duper, and I instruct SD to make a clone of my main drive onto the partition reserved for it.

N'est-ce pas? (My Time Machine is on a separate drive)


Edited by ryck (10/29/11 11:10 PM)
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iMac (Retina 5K, 27", 2017), 3.4 GHz Intel Core i5, 8GB RAM, 2400 MHz DDR4
OS High Sierra 10.13.6
Canon MX710 Printer
Epson Perfection V500 Photo Scanner
Time Machine on 320GB OWC Mercury OTG Pro
Super Duper on 500GB OWC Mercury OTG Pro

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#18777 - 10/29/11 11:29 PM Re: Using DU to Clone Lion to a APM firewire drive [Re: ryck]
artie505 Online


Registered: 08/04/09
> When I make my clone I reboot from the drive that has the system and Super Duper, and I instruct SD to make a clone of my main drive onto the partition reserved for it.

You slipped... You "reboot from into the drive that has the system and Super Duper...."
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#18778 - 10/30/11 01:09 AM Re: Using DU to Clone Lion to a APM firewire drive [Re: artie505]
ryck Online


Registered: 08/04/09
Loc: Okanagan Valley
Originally Posted By: artie505
You slipped... You "reboot from into the drive that has the system and Super Duper...."

....which demonstrates why I'm always at the back of the class. laugh
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ryck

iMac (Retina 5K, 27", 2017), 3.4 GHz Intel Core i5, 8GB RAM, 2400 MHz DDR4
OS High Sierra 10.13.6
Canon MX710 Printer
Epson Perfection V500 Photo Scanner
Time Machine on 320GB OWC Mercury OTG Pro
Super Duper on 500GB OWC Mercury OTG Pro

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#18779 - 10/30/11 01:45 AM Re: Using DU to Clone Lion to a APM firewire drive [Re: ryck]
artie505 Online


Registered: 08/04/09
Originally Posted By: ryck
Originally Posted By: artie505
You slipped... You "reboot from into the drive that has the system and Super Duper...."

....which demonstrates why I'm always at the back of the class. laugh

Please be sure not to sit in my seat. grin
_________________________
The new Great Equalizer is the SEND button.

In Memory Of Harv: Those who can make you believe absurdities can make you commit atrocities. ~Voltaire

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#18781 - 10/30/11 05:27 AM Re: Using DU to Clone Lion to a APM firewire drive [Re: artie505]
dkmarsh Offline

Moderator

Registered: 08/04/09
Originally Posted By: artie505
> When I make my clone I reboot from the drive that has the system and Super Duper, and I instruct SD to make a clone of my main drive onto the partition reserved for it.

You slipped... You "reboot from into the drive that has the system and Super Duper...."

Actually, I think ryck had it right. One boots from a particular volume or device, and boots into a particular OS or mode. Check these Google searches to see what I mean:
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#18784 - 10/30/11 11:03 AM Re: Using DU to Clone Lion to a APM firewire drive [Re: macnerd10]
Hal Itosis Offline


Registered: 09/03/09
Loc: 10.6.8 (build 10K549)
Originally Posted By: macnerd10
Does this mean that you need to have three drives: the active volume that has the cloning software running, the inactive source (also bootable) and the target drive? I kind of doubt that this is a standard setup unless one has a desktop with two drives and an external. Are you guys doing it that way?

Admittedly this is non-"standard" practice, but every disk/drive i own (or have ever owned since the early 90's) is partitioned. The externals have at least one bootable system, and my internal HDs have at least two. I suppose another alternative is a bootable flash drive. [one could also use Disk Utility to do a "restore" (clone) while booted from a system dvd perhaps, but i reserve dvd booting for full-blown emergencies when no other option is available.]

This part of the discussion is mostly about *full* clone operations. Once that has much been achieved successfully, all the "incremental" updates (which both SD and CCC offer) are safe enough in my opinion.

That all goes for Time Machine too i suppose. I was just wondering to myself how they design those programs to run while users are busy renaming, re-saving, and/or moving stuff around in realtime... while the backup is still underway. I guess they have error handlers that silently avoid potential conflicts and deal with them somehow.

That's why a full clone is more susceptible... because it takes so long to complete. If it all happened in one second, not much will have changed from location to location. But the fact that it takes a few minutes increases the chance that "something" might get out of sync (e.g., when one item backed up early on depends on the state of something backed up later in the game). In most cases it might not matter, but there's always a chance that one day . . . it might.



Edited by Hal Itosis (10/30/11 11:06 AM)

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#18785 - 10/30/11 11:08 AM Re: Using DU to Clone Lion to a APM firewire drive [Re: Hal Itosis]
macnerd10 Offline


Registered: 08/04/09
Loc: Los Angeles, CA
I agree with your reasoning, it seems very logical. So, why didn't Apple make a couple of partitions on their computers to facilitate the cloning procedure? We heard a lot of things here about TM "clones" not being bootable… Do they think that only backing up user's data is necessary and the rest can be restored from original disks if push comes to shove?
_________________________
Alex
3.1 GHz 13" MacBook Pro 2015, 8 GB RAM, OS 10.11.2, Office 2011, TimeWarner Cable
2.8 GHz Xeon Mac Pro 2010, 16 GB RAM, OS 10.11.2, Office 2011, LAN

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#18788 - 10/30/11 12:14 PM Re: Using DU to Clone Lion to a APM firewire drive [Re: macnerd10]
Hal Itosis Offline


Registered: 09/03/09
Loc: 10.6.8 (build 10K549)
Originally Posted By: macnerd10
I agree with your reasoning, it seems very logical. So, why didn't Apple make a couple of partitions on their computers to facilitate the cloning procedure?

A brief bit of history: back in 10.1 we had two Apple programs... Disk Utility and Disk Copy. Only the latter was capable of copying disks. Then later (10.2 maybe?) that functionality was merged into DU, and DC was dumped. My recollection is fuzzy, but i think it was during that interim in which CCC came on the scene with its ability to make bootable clones. [can't recall if DC did that or not in OSX, and i'm fairly certain that Super Duper didn't exist yet.]

But anyway, "cloning" to create a bootable backup was never anything that Apple offered initially.. as far as i recall. In fact Mike Bombich went to work for Apple right around the time that CCC and NetRestore were becoming huge hits... so perhaps it was around that same time that DU started to get beefed up. I'm not sure though.

There is a similar phenomenon with Software Update. Remember back in the "modal" days before OSX, when doing a software update meant not being able to do anything else? Then OSX came along and didn't enforce any such restriction. Subsequently, some users would continue browsing or playing WoW whilst a software update was underway... only to show up at MacFixIt's fora later on talkin' 'bout how the update hosed their system.


Originally Posted By: macnerd10
We heard a lot of things here about TM "clones" not being bootable… Do they think that only backing up user's data is necessary and the rest can be restored from original disks if push comes to shove?

You know Apple... everything needs to be (or at least seem) as simple as possible. smile


Edited by Hal Itosis (10/30/11 12:24 PM)

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#18797 - 10/30/11 05:58 PM Re: Using DU to Clone Lion to a APM firewire drive [Re: Hal Itosis]
macnerd10 Offline


Registered: 08/04/09
Loc: Los Angeles, CA
"Subsequently, some users would continue browsing or playing WoW whilst a software update was underway... only to show up at MacFixIt's fora later on talkin' 'bout how the update hosed their system".

Like!
_________________________
Alex
3.1 GHz 13" MacBook Pro 2015, 8 GB RAM, OS 10.11.2, Office 2011, TimeWarner Cable
2.8 GHz Xeon Mac Pro 2010, 16 GB RAM, OS 10.11.2, Office 2011, LAN

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#18798 - 10/30/11 06:12 PM Re: Using DU to Clone Lion to a APM firewire drive [Re: Hal Itosis]
ganbustein Offline


Registered: 08/04/09
Originally Posted By: Hal Itosis
Admittedly this is non-"standard" practice, but every disk/drive i own (or have ever owned since the early 90's) is partitioned. The externals have at least one bootable system, and my internal HDs have at least two.

This is similar to what I do. On every computer that I've ever had that had two internal drives, they were both bootable. When I started using computers with only one internal drive, I started partitioning it into two bootable partitions. Let's call them "Normal" and "Alternate". I partition a same-size external drive the same way, into "Normal2" and "Alternate2". Normally, that external disk is unmounted and powered off, and I'm booted off of "Normal". Time Machine is backing up to a separate external drive.

When I want to back up, the procedure is:
  1. Power up the external.
  2. Use a copy of SuperDuper on Normal to clone Alternate to Alternate2.
  3. Boot off of Alternate (which, incidentally, has Time Machine turned off).
  4. Use a copy of SuperDuper on Alternate to clone Normal to Normal2.
  5. Unmount and turn off the drive containing Normal2/Alternate2.
  6. Run Software Update to bring Alternate up to date.
  7. Update anything else on Alternate that needs updating. (This is quick. Alternate is a nearly-virgin standard OS X install. The only extras are SuperDuper and Xcode.)
  8. Boot off of Normal, logging into the admin account
  9. (Optionally, turn off Time Machine here, if the following steps are expected to be lengthy.)
  10. Run Software Update to bring Normal up to date.
  11. Update anything else that has updates
  12. (Turn Time Machine back on if I turned it off above.)
  13. Log out of the admin account, and back into my normal user account.

Things to notice:
  • I never use SuperDuper to clone the volume I'm booted from.
  • The external backup drive is unmounted and turned off during all software updates, to guard against updaters grabbing the wrong disk.
  • I get a full current backup of everything before it gets updated. If an update botches things, I can back out by restoring from the backup.
  • The last TM snapshot before I start, and the first after I'm done, also give me full before/after versions to restore from. I don't let TM back up a partially updated system.
  • The internal drive (where I work), SuperDuper's external, and TM's external, are three separate drives. Two backups onto the same drive are really only one backup. (There are other externals, for a backup of my TM backup, and offsite backups, but that's another topic.)

Originally Posted By: Hal Itosis
This part of the discussion is mostly about *full* clone operations. Once that has much been achieved successfully, all the "incremental" updates (which both SD and CCC offer) are safe enough in my opinion.

Why would you think that? Any backup of a running system is risky. The "increment" would be mostly my user files, which are the files I care most about.

Originally Posted By: Hal Itosis
That all goes for Time Machine too i suppose. I was just wondering to myself how they design those programs to run while users are busy renaming, re-saving, and/or moving stuff around in realtime... while the backup is still underway.


I wrote a very lengthy post on this topic. TM knows it's backing up a running system, knows its risky, and goes to great lengths to mitigate the downside. I won't repeat the whole thing, but the highlights are:
  • It keeps multiple backups. If one is bad, there are others.
  • It uses the FSEventLog mechanism to locate changed files very quickly, reducing typical backup times from several tens of minutes to several tens of seconds. The list of changed files includes even the files that change while it's building the list.
  • It always does two backups, back to back. The second backup catches all the files that changed during the copy phase of the first backup. The second backup typically takes only a second or two, so it's an almost-simultaneous snapshot of all files everywhere.
  • It has intelligence about which files can be safely backed up while they're being changed. (It knows disk images cannot be backed up while they're mounted read/write; it knows how to get a valid copy of an SQLite database even if it's being updated.)
  • It accepts advice from applications about what can't be backed up. For example, iPhoto tells TM not to back up it's photo library while iPhoto is running.
  • Lion has a feature called File Coordination that lets any application safely copy a document being edited by another application. The editing application needs to support File Coordination, of course, but Finder and Mail both invoke it. I can only imaging that TM on Lion will invoke it too, but I haven't verified this yet.
  • It uses the FSEventStream mechanism to detect files that are changing while being copied. It knows such copies are not to be trusted, and won't keep them.
  • For files that cannot be backed up this time around, it keeps the version from the previous backup, preferring stale data to corrupted data.
  • When, despite precautions, it doesn't trust the backup it just made, it discards it (with an error alert). There'll be another attempt in an hour, or the user can do a Backup Now. Either way, such errors are transient, and the next backup will probably succeed.


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#18800 - 10/30/11 08:15 PM Re: Using DU to Clone Lion to a APM firewire drive [Re: dkmarsh]
artie505 Online


Registered: 08/04/09
Originally Posted By: dkmarsh
Originally Posted By: artie505
> When I make my clone I reboot from the drive that has the system and Super Duper, and I instruct SD to make a clone of my main drive onto the partition reserved for it.

You slipped... You "reboot from into the drive that has the system and Super Duper...."

Actually, I think ryck had it right. One boots from a particular volume or device, and boots into a particular OS or mode. Check these Google searches to see what I mean:

You're correct as relates to ryck's words, "reboot from the drive that has the system and Super Duper," but he hasn't got a drive that's got OS X and SD, rather he's got a partition on a drive that's got them, so his intention is to "reboot into the partition...," and that's what I reacted to.

Edit: In other words, I should have said "You 'reboot from into the drive partition that has the system and Super Duper....'"


Edited by artie505 (10/30/11 09:56 PM)
_________________________
The new Great Equalizer is the SEND button.

In Memory Of Harv: Those who can make you believe absurdities can make you commit atrocities. ~Voltaire

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#18802 - 10/31/11 12:25 AM Re: Using DU to Clone Lion to a APM firewire drive [Re: ganbustein]
macnerd10 Offline


Registered: 08/04/09
Loc: Los Angeles, CA
"The external backup drive is unmounted and turned off during all software updates, to guard against updaters grabbing the wrong disk."

Never happened to me. In fact, Apple software updater only updates the main disk, which is used to boot the computer (it shows with a green downward arrow); my external (bootable and with a clone of the main one) always shows up in orange color with an exclamation mark on it.


Edited by macnerd10 (10/31/11 12:26 AM)
_________________________
Alex
3.1 GHz 13" MacBook Pro 2015, 8 GB RAM, OS 10.11.2, Office 2011, TimeWarner Cable
2.8 GHz Xeon Mac Pro 2010, 16 GB RAM, OS 10.11.2, Office 2011, LAN

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#18803 - 10/31/11 12:57 AM Re: Using DU to Clone Lion to a APM firewire drive [Re: macnerd10]
artie505 Online


Registered: 08/04/09
The OS X 10.6.8 Combo offers to update any eligible volume it can find, but I'm not certain which, if any, other updaters work similarly.

Edit: It just tried, and it offered to update my main volume, my bootable clone on the same disk, and a bootable clone on an external HD.


Edited by artie505 (10/31/11 01:00 AM)

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#18830 - 10/31/11 12:35 PM Re: Using DU to Clone Lion to a APM firewire drive [Re: artie505]
ganbustein Offline


Registered: 08/04/09
The App Store application also tries to update all the copies it can see. It's not always successful. (For example, it keeps complaining that Xcode on my "Alternate" volume is not up to date, even though it actually is, probably because I updated it using the "Install Xcode" application that it downloaded to "Normal". Xcode can only be installed on the boot volume. Irritatingly, the App Store doesn't tell you which copy of an app it thinks is not up to date.) It did update the copy of "Install Mac OS X Lion.app" that I had squirreled away on a different volume where I thought it would be safe.

But I've been doing this for a long time, not because I mistrusted Apple's installers (until now), but because third-party installers are a very mixed bag from vendors with very different levels of competence. I've even seen installers try to update copies of their application on the Time Machine backup. (Fortunately, TM is very good at protecting its backups.)

Another problem, less common than it used to be, is that an alias my resolve to a target on a volume different from the one you expect, especially after you've restored from a backup. (For example, a restored alias may resolve to a file on the backup.) If you even run an application, it may think its documents are on the backup volume, and you'll silently update the wrong document. Then all your changes get wiped out on the next backup. As I say, that's less common now that Apple has changed the algorithm for resolving aliases so that it gives priority to the embedded symlink over the embedded volref and inode numbers.)

And, there was briefly a problem with Apple's installer, in that it would damage a drive using a very specific Firewire interface chip if it was powered on (it didn't need to be mounted) during an install. Apple fixed the problem, and it would never have affected me since I didn't have any drives using that chip, but I still power off my backup drives before running the installer.

Besides, you're going to power off your backups eventually, right? They're too valuable to leave mounted as a tempting target for bugs and/or operator error. Why tempt fate?

Bugs, like clothing styles, come and go, and sometimes come back again. Just because a problem has been fixed doesn't mean it'll stay fixed. Better to let someone else report the resurgence of an old problem than to experience it firsthand.

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#18832 - 10/31/11 01:56 PM Re: Using DU to Clone Lion to a APM firewire drive [Re: artie505]
macnerd10 Offline


Registered: 08/04/09
Loc: Los Angeles, CA
You are right. However, the installer offers to first update the booted disk (green arrow) by default. One can only manually choose the other disk(s). Just updated Microsoft autoupdate and it did not even ask me where to go: updated the booted disk as well. Therefore, my impression that the installers do not install something "by mistake" and try the booted disk first still stands.
_________________________
Alex
3.1 GHz 13" MacBook Pro 2015, 8 GB RAM, OS 10.11.2, Office 2011, TimeWarner Cable
2.8 GHz Xeon Mac Pro 2010, 16 GB RAM, OS 10.11.2, Office 2011, LAN

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#18836 - 10/31/11 02:24 PM Re: Using DU to Clone Lion to a APM firewire drive [Re: macnerd10]
artie505 Online


Registered: 08/04/09
> Therefore, my impression that the installers do not install something "by mistake" and try the booted disk first still stands.

I agree that installers try the booted disk by default, but I can't argue with ganbustein about the "by mistake" part; he's got too much history to my too little.

Apropos of that, did you see his "The App Store application [...] update(d) the copy of "Install Mac OS X Lion.app" that I had squirreled away on a different volume where I thought it would be safe?"
_________________________
The new Great Equalizer is the SEND button.

In Memory Of Harv: Those who can make you believe absurdities can make you commit atrocities. ~Voltaire

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#18837 - 10/31/11 03:27 PM Re: Using DU to Clone Lion to a APM firewire drive [Re: artie505]
macnerd10 Offline


Registered: 08/04/09
Loc: Los Angeles, CA
I think it happens because it must be the only copy the updater can find. Again, does not seem to be a mistake. grin
_________________________
Alex
3.1 GHz 13" MacBook Pro 2015, 8 GB RAM, OS 10.11.2, Office 2011, TimeWarner Cable
2.8 GHz Xeon Mac Pro 2010, 16 GB RAM, OS 10.11.2, Office 2011, LAN

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