djk at tobit.co.uk
Thu Nov 1 13:32:05 GMT 2007
Martin A. Brooks wrote:
> Given Adaptec have managed to release some of the most shamelessly crap
> bits of RAID kit I've ever had the misfortune to use,
Yes, but they were not alone.
> 3ware/Compaq/Mylex hardware raid >
> software RAID >
> Crappy hardware RAID that's really software RAID and/or Adaptec
Depends what you want. Unless the processors in RAID cards have been
significantly beefed up in recent hardware - if it is speed you want -
then software raid wins hands down all the time.
The last time I did some serious benchmarking (3 or 4 years ago now)
software raid beat so called "enterprise" raid hardware - in speed -
(both read and write) by a factor of between 4 and 5 (depending on raid
card manufacturer). IIRC I tested again high end Adaptec and Compaq raid
cards as installed in Dell and Compaq servers respectively. Ironically
this benchmarking was done using the same card either as a raid
controller or just plain scsi. Software raid was always much faster.
Sadly though, software raid was harder to setup, to maintain and to
rebuild after a failure. So it wasn't all good news. Don't know whether
the tools have improved since then (I hope so). Don't do that anymore.
None of this should be hugely surprising as, in those days, the
processor on board the raid card was some otherwise obsolete 400Mhz
Intel part with maybe as much as 256Mb of ram as cache. At the same
time, the servers they were in were dual 2GHz+ Xeons or some such with
4GB RAM. And as these thing were just used basically as file servers, it
is easy to see the reason for the discrepancy.
Don't take your hardware manufacturer's word for it. Use bonny, it will
tell how well it *really* works.
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