Dissapointing performance of ciss RAID 0+1 ?

Pete French petefrench at ticketswitch.com
Thu Nov 9 11:59:39 UTC 2006

> > Raw dd gives 50 meg/second
> On /dev/da1, with a reasonable block size (1m)?

Block size is 2meg. I was using da1s1 and da1s2 which were giving
me 50 and 47 meg/second resepctively - if I switch to da1 on it's
own I get 59 meg/second.

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.


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