If 512B drive is used with 4KiB ashift, there may be a performance lost (as more data will be pushed and read from the drive).
It not so much the drives are lying, just they don't implement the ATAPI standard (for SATA) to tell the OS they are really 4KiB drives. A firmware update would fix this. The modern OpenSolaris children (S11E, OpenIndiana, etc.) all read the physical size correctly when its provided via the drive. Illumos will be providing support at the driver level via a driver look up table quite soon for drives that don't tell the OS the physical block size and I would expect other OS's will also hide the problem at the driver level going forward. For now zpool pool fixes are a reasonable work-around. The previous linked zpool forces 4KiB which might not be ideal if you are also using non 4KiB drives. A link to a zpool with a command line block-size is on the OpenIndiana wiki at this link http://wiki.openindiana.org/oi/SATA+-+Advanced+Format+and+4K+Sector+drives HTH, Deano de...@cloudpixies.com -----Original Message----- From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-boun...@opensolaris.org] On Behalf Of Tomas Ögren Sent: 26 January 2011 17:01 To: zfs-discuss@opensolaris.org Subject: Re: [zfs-discuss] mix 4k wdd drives whit 512 WD drives ? On 26 January, 2011 - Benji sent me these 0,8K bytes: > Those WD20EARS emulate 512 bytes sectors, so yes you can freely mix > and match them with other "regular" 512 bytes drives. Some have > reported slower read/write speeds but nothing catastrophic. For some workloads, 3x slower than it should be. > Or you can create a new 4K aligned pool (composed of only 4K drives!) > to really take advantage of them. For that, you will need a modified > zpool command to sets the ashift value of the pool to 12. A 4k aligned pool will work perfectly on a 512b aligned disk, it's just the other way that's bad. I guess ZFS could start defaulting to 4k, but ideally it should do the right thing depending on content (although that's hard for disks that are lying). /Tomas -- Tomas Ögren, st...@acc.umu.se, http://www.acc.umu.se/~stric/ |- Student at Computing Science, University of Umeå `- Sysadmin at {cs,acc}.umu.se _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
