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

To: Linux fs XFS <xfs@xxxxxxxxxxx>
Subject: Re: XFS: Abysmal write performance because of excessive seeking (allocation groups to blame?)
From: Stefan Ring <stefanrin@xxxxxxxxx>
Date: Fri, 6 Apr 2012 09:27:19 +0200
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References: <CAAxjCEwBMbd0x7WQmFELM8JyFu6Kv_b+KDe3XFqJE6shfSAfyQ@xxxxxxxxxxxxxx> <20350.9643.379841.771496@xxxxxxxxxxxxxxxxxx> <20350.13616.901974.523140@xxxxxxxxxxxxxxxxxx>
> As to this, in theory even having split the files among 4 AGs,
> the upload from system RAM to host adapter RAM and then to disk
> could happen by writing first all the dirty blocks for one AG,
> then a long seek to the next AG, and so on, and the additional
> cost of 3 long seeks would be negligible.

Yes, that’s exactly what I had in mind, and what prompted me to write
this post. It would be about 10 times as fast. That’s what bothers me
so much.

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