From: NeilBrown <neilb@suse.de>
To: Marcus Sorensen <shadowsor@gmail.com>
Cc: linux-raid <linux-raid@vger.kernel.org>
Subject: Re: sync speed strangeness and other advice
Date: Fri, 18 May 2012 07:20:32 +1000 [thread overview]
Message-ID: <20120518072032.1f779bda@notabene.brown> (raw)
In-Reply-To: <CALFpzo6EgYjNKDjq41ZFj1_NL6AYy7OLDF18Zeis5iWd21taRA@mail.gmail.com>
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On Thu, 17 May 2012 09:37:50 -0600 Marcus Sorensen <shadowsor@gmail.com>
wrote:
> First off, I'm using the stock RHEL 6.2 kernel, so obviously not the
> latest, but I want to get some input on a strange issue I'm seeing.
> Maybe it rings a bell and someone knows a fix or a specific kernel to
> try.
Could I get that a as linux-kernel version number? RHEL numbers don't mean
anything to me.
>
> I have a few RAID 1 arrays that while resyncing refuse to use the
> bandwidth allowed to them. I'm using an internal bitmap. My impression
> was that the various sync speed settings are supposed to use all
> available bandwidth, backing off if there is other system activity.
> The disks are capable of syncing at 400MB/s, and my sync_speed_min is
> set to 10000, sync_speed_max is set to 500000, yet they sync at
> ~80MB/s and iostat shows the disks as being mostly idle. If I
> increase sync_speed_min to 200000, the array happily complies and
> resyncs at 200MB/s, no problem.
400MB/s!! SSDs??
The "is the device idle" algorithm was quite fragile for a while there,
though I feel that was quite a while ago.
So it might be a known problem but I would need the kernel version to be sure.
>
> Also, I seem to have run into an issue similar to the following
> thread, where failing a disk, then restarting the array and re-adding
> the disk results in a full resync. I'll see if I can replicate via the
> included instructions.
>
> http://www.mail-archive.com/linux-raid@vger.kernel.org/msg08745.html
>
> Last, I've been reading bits about a bad block bitmap, and if I'm
> going to a newer kernel I want to make sure I'm not using one. My
> understanding was that I have to use a new version of the mdadm
> userspace utility to even create an array with a bad block bitmap, and
> even then it's not on by default, correct?
It isn't a bitmap, it is a list. And it needs to be explicitly enabled by
mdadm, and no released version of mdadm does that.
I don't know yet what the default will be once I do add that support properly.
Suggestions welcome.
NeilBrown
>
> Thanks
> --
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prev parent reply other threads:[~2012-05-17 21:20 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-17 15:37 sync speed strangeness and other advice Marcus Sorensen
2012-05-17 21:20 ` NeilBrown [this message]
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