From: Ric Wheeler <ric@emc.com>
To: Molle Bestefich <molle.bestefich@gmail.com>
Cc: NeilBrown <neilb@suse.de>, linux-raid@vger.kernel.org
Subject: Re: [PATCH 003 of 5] md: Change ENOTSUPP to EOPNOTSUPP
Date: Fri, 28 Apr 2006 12:48:37 -0400 [thread overview]
Message-ID: <44524765.6070703@emc.com> (raw)
In-Reply-To: <62b0912f0604280634x7df2a8a5m9022826876446cb6@mail.gmail.com>
Molle Bestefich wrote:
> NeilBrown wrote:
>
>> Change ENOTSUPP to EOPNOTSUPP
>> Because that is what you get if a BIO_RW_BARRIER isn't supported !
>
>
> Dumb question, hope someone can answer it :).
>
> Does this mean that any version of MD up till now won't know that SATA
> disks does not support barriers, and therefore won't flush SATA disks
> and therefore I need to disable the disks's write cache if I want to
> be 100% sure that raid arrays are not corrupted?
>
> Or am I way off :-).
>
You are absolutely right - if you do not have a validated, working
barrier for your low level devices (or a high end, battery backed array
or JBOD), you should disable the write cache on your RAIDed partitions
and on your normal file systems ;-)
There is working support for SCSI (or libata S-ATA) barrier operations
in mainline, but they conflict with queue enable targets which ends up
leaving queuing on and disabling the barriers.
ric
next prev parent reply other threads:[~2006-04-28 16:48 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-04-28 2:51 [PATCH 000 of 5] md: Introduction - assorted raid10/raid1 fixes NeilBrown
2006-04-28 2:50 ` [PATCH 001 of 5] md: Avoid oops when attempting to fix read errors on raid10 NeilBrown
2006-05-01 21:52 ` [stable] " Greg KH
2006-04-28 2:51 ` [PATCH 002 of 5] md: Fixed refcounting/locking when attempting read error correction in raid10 NeilBrown
2006-04-28 2:51 ` [PATCH 003 of 5] md: Change ENOTSUPP to EOPNOTSUPP NeilBrown
2006-04-28 13:34 ` Molle Bestefich
2006-04-28 16:48 ` Ric Wheeler [this message]
2006-04-29 13:50 ` Molle Bestefich
2006-04-29 20:23 ` Ric Wheeler
2006-05-01 16:14 ` Gil
2006-05-02 1:54 ` Paul Clements
2006-05-02 2:17 ` Mike Hardy
2006-05-02 11:37 ` Ric Wheeler
2006-04-30 4:13 ` [PATCH 003 of 5] " Neil Brown
2006-04-30 5:33 ` Guy
2006-04-30 6:00 ` Neil Brown
2006-04-28 2:51 ` [PATCH 004 of 5] md: Improve detection of lack of barrier support in raid1 NeilBrown
2006-04-28 2:51 ` [PATCH 005 of 5] md: Fix 'rdev->nr_pending' count when retrying barrier requests NeilBrown
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