[CentOS] Calling All FS Fanatics

Kirk Bocek t004 at kbocek.com
Thu Oct 5 16:34:00 UTC 2006

Morten Torstensen wrote:
> Err... are you sure you want to turn on write-caching? You will have
> filesystem corruption in case of a power-down, panic or other crashes
> then. It does help to have a battery backup on the 3ware card, assuming
> it is smart enough to write the changes to disk before the OS starts.

Yea, I'm sure. With write-caching turned off on the 3Ware controller only and
writing to an XFS filesystem:

                 ------Sequential Output------ --Sequential Input- --Random-
                 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine     Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
Beryl     5G:64k  9968  15 10447   1  3924   0 25071  38 201973  18 542.5   3
                 ------Sequential Create------ --------Random Create--------
                 -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
files:max:min     /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
Beryl         16   253   1 +++++ +++   230   1   225   1 +++++ +++   149   1

Block writes drop to 10MB/Sec plus the system becomes non-responsive during
large writes. Can anyone tell me this is acceptable? I'm really at a loss when
you and Feizhou tell me to turn off write-caching. How do you get anything
even approaching *tolerable* performance?

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