I was looking at LaCie User Manuals - Precautions and came across the statement Do not place the LaCie hard drive near sources of magnetic interference, such as computer displays, televisions or speakers. Magnetic interference can affect the operation and stability of your LaCie hard drive.
Given the hard drive in your proposed iMac is a LOT closer to the monitor and CPU than any external HD could possibly be that would imply…
- LaCie enclosures (LaCie does not make drives, just enclosures with third party drives they purchase in bulk from whoever has the lowest price) are incredibly sensitive to electrical interference
- That warning is block copy from a long time ago when CRTs were the rule and not todays LED monitors
- The copy writers are extremely cautious in covering their exposed nether regions
- All of the above
Right now I have an OWC and a NewTech drive enclosures parked directly beneath my monitor and have never had a seconds problem with either. I am not a particular fan of LaCie but they are better engineers than to build an enclosure that sensitive to magnetic fields.
The LaCie drives run at 5400 rpm but the connection speed via Thunderbolt is super fast. Given the choice between a 7200 rpm drive on USB 3 and a 5400 rpm drive on Thunderbolt, which would have faster data transfer?
There are other factors than rotation speed that can have a major effect on perceived drive performance. If you are transferring lots of small data files and/or the drive is badly fragmented a 7200 RPM drive will generally yield better performance. If you are transferring large data files the sustained data transfer rate of the drive is more important and 5400 RPM drives may be capable of higher sustained data transfer rates than some 7200 RPM drives. In external enclosures you also have to consider the sustained data transfer rate of the enclosure's SATA bridge chip. The drive may be capable of 6 Mbps and the bridge chip can only handle 3 Mbps.
Little "gotchas" like that long ago drove me to buying bare enclosures and installing my own hard drive. By doing that I am able to optimize system performance to match my personal application needs. Besides that I found buying an enclosure with a drive pre-installed usually limited the warranty for both to one year whereas buying them separately I can end up with a one year warranty on the enclosure and three to five years on the drive. In my experience the drive is more likely to fail than the enclosure is. I have one little enclosure that has outlived two drives. Of course the FW400 interface in that enclosure is relatively antiquated by today's standards, but for some situations it continues to soldier valiantly along.
FWIW I have been duly impressed by the performance of the USB 3 interface in my NewerTech MaxMini enclosure. All things are not equal but comparing the performance of the NewerTech on USB 3 with an OWC enclosure on FW800 shows the USB 3 to be roughly 45% faster. (No guarantees on that as there are too many other variables that are not controlled but a reasonable approximation.
If you want absolute maximum drive performance using the Thunderbolt port you really need to consider a RAID 1 or Raid 5 enclosure. OWC has one that used 3.5" drives and another less expensive one that uses 2.5" drives. Of course by the time you add 4 1TB drives you are looking at nearly $700 but blazing performance.
