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Re: extremely slow write performance plaintext

To: xfs@xxxxxxxxxxx
Subject: Re: extremely slow write performance plaintext
From: Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx>
Date: Fri, 14 Jan 2011 13:51:33 -0600
In-reply-to: <18993_1294964274_4D2F9632_18993_1387_1_F79CF9ADB27B2646B59221B7355263830CC143B1@xxxxxxxxxxxxxxxxxxxxxxxx>
References: <3205_1294953756_4D2F6D1C_3205_1943_1_4D2F6D1C.2060409@xxxxxxxxxxxxxxx> <20110113233527.6dca104d@xxxxxxxxxxxxxx> <18993_1294964274_4D2F9632_18993_1387_1_F79CF9ADB27B2646B59221B7355263830CC143B1@xxxxxxxxxxxxxxxxxxxxxxxx>
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Cory Coager put forth on 1/13/2011 6:17 PM:

>   --- Physical volume ---
>   PV Name               /dev/cciss/c1d1p1
>   VG Name               vg0
>   PV Size               2.94 TB / not usable 1.51 MB
>   Allocatable           yes
>   PE Size (KByte)       4096
>   Total PE              769902
>   Free PE               562351
>   Allocated PE          207551
>   PV UUID               IAZAbk-eMNZ-puMJ-DqW1-zsC7-C0ux-66vYTN

Make sure the write cache on the P600 (what size is it BTW?) is enabled and that
the BBU is in working order.  Also make sure the P600 is disabling the write
caches on the drives themselves.  Then...

Mount with 'nobarrier' so XFS isn't interfering with the hardware cache
performance of the P600.  With barriers enabled (the default) XFS will
periodically flush the cache on the RAID card causing write performance 


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