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.

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 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. 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 ;)

HTH,
//Jim


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