atom feed19 messages in org.opensolaris.zfs-discussRe: [zfs-discuss] Does your device ho...
FromSent OnAttachments
Bryant EadonFeb 10, 2009 10:35 am 
Peter SchullerFeb 10, 2009 10:52 am 
Miles NordinFeb 10, 2009 11:23 am 
Chris RiddFeb 10, 2009 11:27 am 
TimFeb 10, 2009 12:19 pm 
Peter SchullerFeb 10, 2009 1:36 pm 
David Collier-BrownFeb 10, 2009 1:55 pm 
Miles NordinFeb 10, 2009 2:56 pm 
Peter SchullerFeb 10, 2009 3:45 pm 
Bob FriesenhahnFeb 10, 2009 4:08 pm 
Jeff BonwickFeb 10, 2009 4:41 pm 
Toby ThainFeb 10, 2009 5:23 pm 
Miles NordinFeb 10, 2009 6:10 pm 
Frank CusackFeb 10, 2009 7:36 pm 
Toby ThainFeb 10, 2009 8:53 pm 
Bryant EadonFeb 10, 2009 10:28 pm 
Eric D. MudamaFeb 11, 2009 12:25 am 
David Dyer-BennetFeb 11, 2009 7:27 am 
Frank CusackFeb 11, 2009 8:24 am 
Subject:Re: [zfs-discuss] Does your device honor write barriers?
From:Eric D. Mudama (edmu@bounceswoosh.org)
Date:Feb 11, 2009 12:25:39 am
List:org.opensolaris.zfs-discuss

On Tue, Feb 10 at 16:41, Jeff Bonwick wrote:

Not if the disk drive just *ignores* barrier and flush-cache commands and returns success. Some consumer drives really do exactly that. That's the issue that people are asking ZFS to work around.

Can someone please name a specific device (vendor + model + firmware revision) that does this? I see this claim thrown around like fact repeatedly, and yet I've never personally experienced an actual "consumer" device that discarded FLUSH CACHE (EXT) before, and nobody I know can name one that did.

The only exceptions that might "appear" to be ignoring a barrier that I've witnessed are "high fly" writes in rotating drives, where the servo system couldn't detect that the head struck a defect and was deflected too high to write, and devices that don't support the command at all (and thus abort 51/04 attempts to flush the cache).

BTW, funky/busted bridge hardware in external USB devices don't count. I'm more interested in major rotating drive vendors... Seagate/Maxtor, WD, Hitachi/IBM, Fujitsu, Toshiba, etc.

--eric