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 _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
