* XFS without write barriers - safe on multipath device?
@ 2009-01-16 22:09 Adam Fried-Gintis
2009-01-16 22:31 ` Eric Sandeen
0 siblings, 1 reply; 2+ messages in thread
From: Adam Fried-Gintis @ 2009-01-16 22:09 UTC (permalink / raw)
To: xfs
Hi,
I am just curious, if I see the warning that write barrier support is
disabled when mounting an XFS filesystem through md multipath, does XFS have
some OTHER provision for protecting the order of its writes to the
underlying device, or is it unsafe to run with write back caching at that
point? My underlying device is an active/active storage system - combined
with the multipath driver, we are seeing metadata corruption on the
filesystem, and I'm just trying to figure out if this is an invalid
configuration to test or if the storage device is doing something wrong.
Thanks!
---
Adam Fried-Gintis
[[HTML alternate version deleted]]
_______________________________________________
xfs mailing list
xfs@oss.sgi.com
http://oss.sgi.com/mailman/listinfo/xfs
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: XFS without write barriers - safe on multipath device?
2009-01-16 22:09 XFS without write barriers - safe on multipath device? Adam Fried-Gintis
@ 2009-01-16 22:31 ` Eric Sandeen
0 siblings, 0 replies; 2+ messages in thread
From: Eric Sandeen @ 2009-01-16 22:31 UTC (permalink / raw)
To: Adam Fried-Gintis; +Cc: xfs
Adam Fried-Gintis wrote:
> Hi,
> I am just curious, if I see the warning that write barrier support is
> disabled when mounting an XFS filesystem through md multipath, does XFS have
> some OTHER provision for protecting the order of its writes to the
> underlying device, or is it unsafe to run with write back caching at that
> point? My underlying device is an active/active storage system - combined
> with the multipath driver, we are seeing metadata corruption on the
> filesystem, and I'm just trying to figure out if this is an invalid
> configuration to test or if the storage device is doing something wrong.
XFS needs to know that when the storage says a write is complete, that
it really is safe on disk.
You're ok w/o barriers if either:
a) you have no write cache, or
b) you know your write cache is guaranteed to hit the disks (UPS?)
Also, this only comes into play when the drives lose power and lose
their write cache. If that's not happening to you, then your problem is
likely not related to barrier issues.
When you say active/active; do you have 2 hosts directly accessing the
same filesystem on a SAN?
-Eric
> Thanks!
>
> ---
> Adam Fried-Gintis
_______________________________________________
xfs mailing list
xfs@oss.sgi.com
http://oss.sgi.com/mailman/listinfo/xfs
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2009-01-16 23:13 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2009-01-16 22:09 XFS without write barriers - safe on multipath device? Adam Fried-Gintis
2009-01-16 22:31 ` Eric Sandeen
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox