On Tuesday, 13 June 2000 at 16:39:01 -0700, Jaye Mathisen wrote:
>
> I was just curious what people's thoughts were on the potential "total
> system throughput" (whatever you choose it to be), wrt using software
> RAID.
>
> It would seem that software RAID would just kill big chunks of
> cache, especially CPU cache, moving lots of data throught it to
> calcuate CRC's.
Hmm. Yes, it might seem that way, but that's a very different order
of magnitude from the I/O transfers themselves.
> perhaps the raid 1/0's would be fine, since the calcuation could be
> ignored.
Well, there is no calculation.
> It would seem that for file-server type tasks, where hopefully CPU
> is not an issue, then as long as you can exceed the capacity of your
> network, you're probably fine.
>
> And most workstations probably don't run 100% (modulo things like
> the various crackers and seti), that it's a non issue.
It's a non-issue anyway. The RAID-5 parity calculations don't take up
any time. The real issue is that each write requires two physical
reads and two physical writes, reducing write performance to about 25%
of the performance of RAID-1 writes. Take a look through
http://www.lemis.com/vinum.html for further details.
Greg
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