On Sun, Jul 26 at 1:47, David Magda wrote:
On Jul 25, 2009, at 16:30, Carson Gaspar wrote:
Frank Middleton wrote:
Doesn't this mean /any/ hardware might have this problem, albeit
with much lower probability?
No. You'll lose unwritten data, but won't corrupt the pool, because
the on-disk state will be sane, as long as your iSCSI stack doesn't
lie about data commits or ignore cache flush commands.
But this entire thread started because Virtual Box's virtual disk /
did/ lie about data commits.
Why is this so difficult for people to understand?
Because most people make the (not unreasonable assumption) that disks
save data the way that they're supposed to: that the data goes in is
the data that comes out, and that when the OS tells them to empty the
buffer that they actually flush it.
It's only us storage geeks that generally know the ugly truth that
this assumption is not always true. :)
Can *someone* please name a single drive+firmware or RAID
controller+firmware that ignores FLUSH CACHE / FLUSH CACHE EXT
commands? Or worse, responds "ok" when the flush hasn't occurred?
Everyone on this list seems to blame lying hardware for ignoring
commands, but disks are relatively mature and I can't believe that
major OEMs would qualify disks or other hardware that willingly ignore
commands.
--eric
--
Eric D. Mudama
edmud...@mail.bounceswoosh.org
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