> 2012-07-23 18:37, Anonymous wrote:
> > Really, it would be so helpful to know which drives we can buy with
> > confidence and which should be avoided...is there any way to know from the
> > manufacturers web sites or do you have to actually buy one and see what it
> > does? Thanks to everyone for the info.
> I think that vendors' marking like 512e may give a clue on
> their support of "emulated 512-byte sectors", whatever they
> would mean by that for a specific model line.
Yeah but buying through the mail it's awfully difficult to see the vendor
markings until it's too late ;)
> I believe you can roughly be certain that all 3Tb HDDs except
> Hitachi use 4Kb native sectors, and 4Tb disks are all 4Kb.
> If these disks don't expose such sector sizing to the OS
> properly, you can work around that in several ways, including,
> as of recent illumos changes, an override config file for the
> SCSI driver.
The question was relative to some older boxes running S10 and not planning
to upgrade the OS, keeping them alive as long as possible...
> The main problem with "avoiding" 4kb drives seems to be just
> the cases where you want to replace a single disk in an older
> pool built with 512b-native sectored drives.
Right, that's what we're concerned with.
> For new pools (or rather new complete top-level VDEVs) this does not
> matter much, except that your overheads with small data blocks can get
> noticeably bigger.
> There were statements on this list that drives emulating 512b
> sectors (whether they announce it properly or not) are not
> all inherently evil - this emulation by itself may be of some
> concern regarding performance, but not one of reliability.
> Then again, firmware errors are possible in any part of the
> stack, of both older and newer models ;)
I haven't seen any post suggesting 512b emulation didn't have very adverse
effects on performance. Given how touchy ZFS seems to be I don't want to
give him any excuses! Thanks for your post.
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