> worst case). The worst case for 512 emulated sectors on zfs is
> probably small (4KB or so) synchronous writes (which if they mattered
> to you, you would probably have a separate log device, in which case
> the data disk write penalty may not matter).
> Good to know. This really opens up the possibility of buying 3 or 4TB
> Hitachi drives. At least the 4TB Hitachi drives are 4k (512b emulated)
> drives according to the latest news.
It appears from the specs listed on the hitachi site that the drives I
have may actually be 512 native, in which case my testing was moot.
This does explain some other things I saw testing the drives in
question, so I will assume they are 512 native, and that my testing
was meaningless. If you copy folders containing thousands of small
files frequently, the performance impact may be relevant, if you go
for the 512 emulated drives.
> So what you are saying is that something like this will do the trick?
> If I interpret this correctly I get a SFF-8087 to SFF-8088 bracket, connect
> the 4 port LSI SFF-8077 to that bracket, then get a cable for this JBOD and
> throw in 4 drives? This would leave me with four additional HDDs without any
> SAS expander hassle. I had not come across these JBODs. Thanks a million for
> the hint.
No problem, and yes, I think that should work. One thing to keep in
mind, though, is that if the internals of the enclosure simply split
the multilane SAS cable into 4 connectors without an expander, and you
use SATA drives, the controller will use SATA mode, which as I
understand it runs at a lower signalling voltage, and won't work over
long cables, so get a short cable (1 meter, shorter if you can find
one). It looks like all of the ones mentioned so far use this method,
though it would be good to know if Carson populated his with SATA
> Do we agree that for a home NAS box a Hitachi Deskstar (not explicitly being
> a server SATA drive) will suffice despite potential TLER problems? I was
> thinking about Hitachi Deskstar 5k3000 drives. The 4TB seemingly came out
> but are rather expensive in comparison…
I'm not sure what ZFS's timeout for dropping an unresponsive disk is,
or what it does when it responds again, so I don't know if TLER would
help. I have not had any serious problems with my pool of hitachi 3TB
5400 drives. Two different drives had a checksum error, once each,
but stayed online in the pool.
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