Dissapointing performance of ciss RAID 0+1 ?

Pete French petefrench at ticketswitch.com
Thu Nov 9 12:52:26 UTC 2006

> 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.

On the file: KB/t is about 127.5 with both sizes. Rate is 39 on with
the read_max set to 8, but 115 with read_max set to 64.

On the raw device: KB/t is always 128. rate is 41 with the size set to 8
but rises to 57 with the size set to 64! How can the vfs parameters affect
access to the raw device ?

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

On the file: read_max=8 gives 75% busy, 42 meg/sec. 64 gives 99.7% and 120
On the device: both sizes give the same results - 98% busy, 59 meg/second

I am not sure this is helping my understanding! :-)


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