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#37208 - 11/16/15 05:52 AM How inviolate are volumes/partitions?
Pendragon Offline


Registered: 08/04/09
Loc: Georgetown, Texas, USA
In another post (thread 37181), joemike noted: “…Apple does not recommend putting the Time Machine backups on a drive with any other files. Not even if you put the Time Machine data set in a separate partition.

That caught my attention as I thought partitions were inviolate. And if they are not inviolate, can it also be that different volumes are likewise not inviolate?

And to make matters worse, is the answer dependent on whether the drive is spinning or SSD?

Clearly, I am confused. So please, any info/clarification will be appreciated.
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#37216 - 11/16/15 08:09 AM Re: How inviolate are volumes/partitions? [Re: Pendragon]
tacit Offline


Registered: 08/03/09
Loc: Portland, Oregon, USA
They are. The information on one partition doesn't know or care what's on another.

I suspect the reasoning is more about backup reliability and speed, and less about any kind of problem with combining Time Machine data and other data.

Backup reliability: Backup storage devices should not be used for day to day operations, or they may fail when you need them most. hey should be used as little as possible to maximize their lifespan.

Speed: If you are reading from or writing to the TM drive while a TM backup is running, that may impact the speed of the backup, even if you're reading from or writing to a different partition on the drive.
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#37220 - 11/16/15 12:29 PM Re: How inviolate are volumes/partitions? [Re: tacit]
Pendragon Offline


Registered: 08/04/09
Loc: Georgetown, Texas, USA
Many thanks, Tacit. Good info, indeed. Though it does seem odd that speed and/or reliability would be affected to the extent that caution is called for. To me, it smacks of the rationale that if you don't use your drive it will last longer and be more relaible. confused
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#37224 - 11/16/15 01:25 PM Re: How inviolate are volumes/partitions? [Re: Pendragon]
artie505 Online


Registered: 08/04/09
Here is joemike's response to your question.
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#37225 - 11/16/15 02:38 PM Re: How inviolate are volumes/partitions? [Re: artie505]
Pendragon Offline


Registered: 08/04/09
Loc: Georgetown, Texas, USA
Thanks, Artie.

I may be beginning to understand and appreciate the nuances here, but only with respect to SSDs (I still don't see the problem with spinning drives).

I don't doubt the counsel is sound, it's only that I would be uncomfortable explaining all this to others. And to me, that is a clue is clue that my understanding ain't really what it ought to be...
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#37226 - 11/16/15 07:06 PM Re: How inviolate are volumes/partitions? [Re: artie505]
ryck Offline


Registered: 08/04/09
Loc: Okanagan Valley
Originally Posted By: artie505
Here is joemike's response to your question.

Really? I had originally thought about tacking my question onto Pendragon's thread until I realized my question wasn't the same. I ask about adding files to a Time Machine drive without being in a separate partition. i.e. the Time Machine data and the other files are in the same partition. I assumed that, without the barrier of a partition, the problem might be more serious.


Edited by ryck (11/16/15 07:08 PM)
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#37227 - 11/16/15 11:26 PM Re: How inviolate are volumes/partitions? [Re: ryck]
artie505 Online


Registered: 08/04/09
Quoting ryck: "Really?"

Actually, joemike's post in your thread doesn't specifically deal with your question; it only specifically addresses your intro, which is more or less Harv's question.

Originally Posted By: ryck
In another post joemike noted: “…Apple does not recommend putting the Time Machine backups on a drive with any other files. Not even if you put the Time Machine data set in a separate partition."

I assume this means files that share the drive on an ongoing basis. What does it mean for files that are temporarily stored on a Time Machine drive, not in a separate partition? (Emphasis added)

Originally Posted By: Harv
In another post (thread 37181), joemike noted: “…Apple does not recommend putting the Time Machine backups on a drive with any other files. Not even if you put the Time Machine data set in a separate partition.

That caught my attention as I thought partitions were inviolate. (Emphasis added)

Originally Posted By: joemike
That is Apple's recommendation and I have always "understood" the reason was primarily to leave as much space free on the Time Machine disk as possible to avoid backups falling off the back end of the set prematurely! (Emphasis added)

On the other hand, though, tacit has specifically addressed your question in this thread...

Originally Posted By: tacit
I suspect the reasoning is more about backup reliability and speed, and less about any kind of problem with combining Time Machine data and other data.


Edited by artie505 (11/17/15 01:23 AM)
Edit Reason: Add quotes
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#37228 - 11/16/15 11:37 PM Re: How inviolate are volumes/partitions? [Re: Pendragon]
artie505 Online


Registered: 08/04/09
Originally Posted By: Harv
That caught my attention as I thought partitions were inviolate. And if they are not inviolate, can it also be that different volumes are likewise not inviolate?

Unless I'm mistaken, Harv, you've got a nomenclature issue going there: a partition is a volume.

Edit:
Originally Posted By: Harv
I may be beginning to understand and appreciate the nuances here, but only with respect to SSDs (I still don't see the problem with spinning drives).

I don't follow your differentiation between SSDs and HDDs as respects the issue.


Edited by artie505 (11/16/15 11:43 PM)
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#37234 - 11/17/15 09:00 AM Re: How inviolate are volumes/partitions? [Re: Pendragon]
joemikeb Offline
Moderator

Registered: 08/04/09
Loc: Fort Worth, Texas
Originally Posted By: Pendragon
Thanks, Artie.

I may be beginning to understand and appreciate the nuances here, but only with respect to SSDs (I still don't see the problem with spinning drives).

I don't doubt the counsel is sound, it's only that I would be uncomfortable explaining all this to others. And to me, that is a clue is clue that my understanding ain't really what it ought to be…

As far as Time Machine or OS X (and the same is true for Windows, Ubuntu, Unix, etc.) is concerned they see exactly the same logical drive regardless of whether the drive is a rotating media HD or an SSD. The intelligence/firmware in the drive itself is specifically designed to make the physical layout of data on the drive as well as the actual storage media invisible to the operating system and therefore to applications. That is the principal function of the IDE/PATA/SATA interface.

The OS views Fusion Drives and even multi-drive RAID arrays as having the same logical structure as a single HD or SSD but there is an additional layer of abstraction either in software or hardware required to make that happen.
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#37248 - 11/18/15 03:35 AM Re: How inviolate are volumes/partitions? [Re: joemikeb]
Pendragon Offline


Registered: 08/04/09
Loc: Georgetown, Texas, USA
Originally Posted By: joemikeb
Originally Posted By: Pendragon
Thanks, Artie.

I may be beginning to understand and appreciate the nuances here, but only with respect to SSDs (I still don't see the problem with spinning drives).

I don't doubt the counsel is sound, it's only that I would be uncomfortable explaining all this to others. And to me, that is a clue is clue that my understanding ain't really what it ought to be…

As far as Time Machine or OS X (and the same is true for Windows, Ubuntu, Unix, etc.) is concerned they see exactly the same logical drive regardless of whether the drive is a rotating media HD or an SSD. The intelligence/firmware in the drive itself is specifically designed to make the physical layout of data on the drive as well as the actual storage media invisible to the operating system and therefore to applications. That is the principal function of the IDE/PATA/SATA interface.

The OS views Fusion Drives and even multi-drive RAID arrays as having the same logical structure as a single HD or SSD but there is an additional layer of abstraction either in software or hardware required to make that happen.


That explanation, joemike, helped a lot. Progress has been made.

In a way, this reminds me of quantum physics-- I understand it (pretty much, sorta) when working at it. But should I return to the issue in a few weeks, a cerebral restart is required.
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#37254 - 11/18/15 06:22 AM Re: How inviolate are volumes/partitions? [Re: artie505]
Virtual1 Offline


Registered: 08/04/09
Loc: Iowa
Originally Posted By: artie505
Unless I'm mistaken, Harv, you've got a nomenclature issue going there: a partition is a volume.

Not sure if splitting hairs here or if I'm using it wrong, but I've always assumed a volume is a data partition, like one formatted HFS/NTFS/FAT32. Other types could be "Free", "drivers", etc. OS 9 had typically around 9 different partitions on any given drive, only one was the Macintosh HD. The others were the drivers needed for the older machines to boot the drive. Macintosh HD may be on partition disk0s8 for example. Also, technically, the entire device is a partition too. It's the first partition on the drive, which describes itself.
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