[lug] USB3 vs eSATA III question

Lee Woodworth blug-mail at duboulder.com
Sun Jul 22 19:22:07 MDT 2018

On 07/22/2018 12:27 PM, Bear Giles wrote:
> This is mostly from curiousity...

Not related to performance, but something to consider with USB connected hdds
(native or enclosure): in my experience they can do lots of head load/unloads
which might be an issue with premature aging. For one drive smartctl reports
81462 head load/unload cycles. Started out with an interpreted value of 100,
current is 60 with a fail threshold of 0. 20222 (~2.3yr) head flying hours,
40E9 lbas read and written (pvr recording/replaying full-hd ota broadcasts).

I end up arranging for smartctl -d sat -s apm,off /dev/sda at boot for USB
connected drives. I didn't do that for one wd drive and it has
1E6 head load/unloads.

A performance related issue would be hdd RPMs. External USB disks may be
5200 rpm vs. 7200 for internal hdds. Power saving modes can also cause
delays for infrequently accessed drives. If the drive isn't spinning, it
looks to take 1-2 secs to come back online. In my experience, desktop oriented
drives that aren't 'green' don't spin down the platters.

> USB 3 has a claimed bandwidth of 3 Gbps.
> eSATA II has a claimed bandwidth of 3 Gbps, and eSATA III has a claimed
> benefit of 6 Gbps.
> I don't think any USB stick is going to be pushing 3 Gbps (but I'm not 100%
> certain), but perhaps an external hard drive, esp. an external SSD. But is
> that actually realistic?
> In contrast my experience with eSATA is that it really is akin a
> traditionally installed disk.
> Like I said this is mostly from curiosity. I noticed my recent systems
> haven't had eSATA ports but it's easy to add a half-height card for one.
> Ditto external drives - they usually only have USB 3 but if you buy an
> external drive case for your own drive then it's easy to find them with
> both USB 3 and eSATA. So I have my eSATA gear but it might not be necessary
> any longer if the quoted USB 3 numbers are accurate.
> Does anyone else have experience with both USB 3 and eSATA?
> (Meanwhile I'm wondering what to do with a few old external drives that are
> USB 2. They're so much slower and smaller than my external USB 3 drives.)
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