Dissapointing performance of ciss RAID 0+1 ?

Ivan Voras ivoras at fer.hr
Thu Nov 9 12:38:33 UTC 2006

Pete French wrote:

> reading from the filesystem with the vfs.read_max set to 64 I now get
> 112 meg/second though ?!!! how can the filesystem give me better performance
> than the raw device ? I do not think this is  a caching issue as I am using
> a test file nearly twice the size of the RAM in the system to get round this.
> I am delighted by the performance increase, but the results do not make sense.

It would be interesting for you to track iostat (i.e. run "iostat 1") 
with and without modified vfs.read_max and see if there's a difference.

In a similar experiment, you could watch gstat (also before and after) 
and see if it reports the difference.

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