xfs
[Top] [All Lists]

Re: XFS: Abysmal write performance because of excessive seeking (allocat

To: stan@xxxxxxxxxxxxxxxxx
Subject: Re: XFS: Abysmal write performance because of excessive seeking (allocation groups to blame?)
From: Stefan Ring <stefanrin@xxxxxxxxx>
Date: Tue, 10 Apr 2012 23:00:12 +0200
Cc: Martin Steigerwald <Martin@xxxxxxxxxxxx>, Christoph Hellwig <hch@xxxxxxxxxxxxx>, xfs@xxxxxxxxxxx
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; bh=zkJF50GiR1jLgRU7u3KErh8cUZOnYmQKfnezlxyLjo8=; b=PtiomPWGU8U5yZiup1vGcNhIUSuufQliHomXvCPv6YG/xdJ6meFKsVBWlD0YaXzV8u Ws5mU76wYMqTbNnHHNze7gk8EhQtfz3qJhShn/eskwawFXMcw1YHJM4A2u0HozIDD0HM tFpgS7rCkm76ARxwISnPlopDNon89LS/hdHZtlOxtT4TG2gnLiZn9bq6XR2e4gOWTqQP q/ogPjstQzPJQZO0d+XuVtR55QxYwodYdW4LlHxchQn7L8KdHgD8PcV4iEdYNB8askwo jI5c2pVmp+jQtiGjomsB0XRHpgo1ks728bV+YtlD80K53XUUU02nCMuJvlAzTbai+RmM VdpQ==
In-reply-to: <4F849BAE.6070901@xxxxxxxxxxxxxxxxx>
References: <CAAxjCEwBMbd0x7WQmFELM8JyFu6Kv_b+KDe3XFqJE6shfSAfyQ@xxxxxxxxxxxxxx> <20120405213740.GA22824@xxxxxxxxxxxxx> <CAAxjCExBcaB6J-u7ivZKWnKiF7oP10JRxzKzQNRuppHkTE2Tzw@xxxxxxxxxxxxxx> <201204072057.38286.Martin@xxxxxxxxxxxx> <CAAxjCEzRa7CpbA9iESEDjmWQMsJTjkWHJj69ADOXDa4CiRpx3w@xxxxxxxxxxxxxx> <4F849BAE.6070901@xxxxxxxxxxxxxxxxx>
> Is the LVM volume aligned to the RAID stripe?  Is their a partition atop
> the RAID LUN and under LVM?  Is the partition aligned?  Why LVM anyway?

Yes, it is aligned. I followed the advice from
<http://www.mysqlperformanceblog.com/2011/06/09/aligning-io-on-a-hard-disk-raid-the-theory/>.

Why LVM? Because we use it on lots of servers, and there is some value
to having a somewhat similar setup in development as in production.
I’ve done similar tests time and again with LVM and without, and I’ve
never ever measured a significant difference. I haven’t re-tested it
this time, true, but I would be surprised if it would magically behave
completely differently this time.

> The devil is always in the details.  Were you using partitions and LVM
> with the RAID1 concat tesing?  With the free space testing?

I used LVM linear for the concatenation – one volume group made from 3
physical volumes. The pvols were on primary partitions. The one-volume
RAID 6 is set up similarly; from only one pvol of course.

> I assumed you were directly formatting the LUN with XFS.  With LVM and
> possibly partitions involved here, that could explain some of the
> mediocre performance across the board, with both EXT4 and XFS.  If one
> wants maximum performance from their filesystem, one should typically
> stay away from partitions and LVM, and any other layers that can slow IO
> down.

I don’t want maximum performance, I want acceptable performance ;).
This means, I am satisfied with 80% or more of what’s possible, but
I’m not satisfied with 15%.

<Prev in Thread] Current Thread [Next in Thread>