Re: wishful thinking about atomic, multi-sector or full MD stripewidth, writes in storage

From: Ric Wheeler
Date: Fri Sep 04 2009 - 17:30:24 EST

On 09/04/2009 05:21 PM, Mark Lord wrote:
Ric Wheeler wrote:
You must disable the write cache on these commodity drives *if* the MD RAID level does not support barriers properly.

Rather than further trying to cripple Linux on the notebook,
(it's bad enough already)..

People using MD on notebooks (not sure there are that many using RAID5 MD) could leave their write cache enabled.

How about instead, *fixing* the MD layer to properly support barriers?
That would be far more useful, productive, and better for end-users.


Fixing MD would be great - not sure that it would end up still faster (look at md1 devices with working barriers with compared to md1 with write cache disabled).

In the mean time, if you are using MD to make your data more reliable, I would still strongly urge you to disable the write cache when you see "barriers disabled" messages spit out in /var/log/messages :-)


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at