From: Josef Bacik <jbacik@fusionio.com>
To: Martin <m_btrfs@ml1.co.uk>
Cc: <linux-btrfs@vger.kernel.org>
Subject: Re: raid1 inefficient unbalanced filesystem reads
Date: Fri, 28 Jun 2013 11:34:18 -0400 [thread overview]
Message-ID: <20130628153418.GW4288@localhost.localdomain> (raw)
In-Reply-To: <kqk4sc$t5d$1@ger.gmane.org>
On Fri, Jun 28, 2013 at 02:59:45PM +0100, Martin wrote:
> On kernel 3.8.13:
>
> Using two equal performance SATAII HDDs, formatted for btrfs raid1 for
> both data and metadata and:
>
> The second disk appears to suffer about x8 the read activity of the
> first disk. This causes the second disk to quickly get maxed out whilst
> the first disk remains almost idle.
>
> Total writes to the two disks is equal.
>
> This is noticeable for example when running "emerge --sync" or running
> compiles on Gentoo.
>
>
> Is this a known feature/problem or worth looking/checking further?
So we balance based on pids, so if you have one process that's doing a lot of
work it will tend to be stuck on one disk, which is why you are seeing that kind
of imbalance. Thanks,
Josef
next prev parent reply other threads:[~2013-06-28 15:34 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-28 13:59 raid1 inefficient unbalanced filesystem reads Martin
2013-06-28 15:34 ` Josef Bacik [this message]
2013-06-28 15:39 ` Hugo Mills
2013-06-28 15:56 ` Duncan
2013-06-28 16:25 ` Martin
2013-06-28 16:55 ` George Mitchell
2013-06-28 17:04 ` Josef Bacik
2013-06-28 17:45 ` Martin
2013-06-29 9:41 ` Russell Coker
2013-06-29 14:04 ` Martin
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