Re: File system performance, hardware performance, ext3, 3ware RA ID1, etc.

[Daniel Blueman]

Tim,

Do you get the same numbers (but slightly higher, as this is will measure
from a smaller portion of outer zones) with:

# hdparm -t /dev/sda

?

> Adam Radford wrote:
> > Perhaps you are issuing non purely sequential IO.  The card firmware
> does
> > some 
> > reodering, but at some point it will cause performance degradation.  Can
> you
> > try 
> > kernel 2.6 w/xfs? 
> 
> Not any time soon, but as I mentioned earlier, I measured 13.9 megs/sec 
> when I ran this command:
> 
>      time dd if=/dev/zero of=/dev/sda2 bs=1024k count=1024
> 
> No file system was involved; I was simply writing zeros to the block 
> device (swap partition with swap off).  It took 73.522 seconds to do the 
> above operation.  Also, I was running in single-user mode while doing 
> the test.
> 
> > 
> > Also, in my experience, the 'raw io' interface doesn't issue any
> > asynchronous IO.  The
> > card _definately_ needs asynchronous IO posted to it or you will not get
> > good results
> > because you won't get all the drives busy.
> 
> With RAID1, both drives will be written with the same data.  There is no 
> need to be asynchronous, since it's all completely linear and sequential 
> with large data blocks.

-- 
Daniel J Blueman

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