external raid arrays

W Bauske wsb at paralleldata.com
Thu Feb 21 14:57:27 EST 2002


Chris Black wrote:
> 
> We are looking for an external RAID solution that will provide at LEAST
> 100MB/s read bandwidth, probably under RAID 10 (0+1). So far I have been
> disappointed with performance for external raid arrays that we have
> looked into, and I haven't found a good site with actual benchmarks
> for external raid arrays. So I'm using the list :)
> I know some of you probably have some experience in high performance
> external raid solutions so I'm asking for tips, suggestions, links, etc.
> I don't care if it is an Ultra160 connect or fibre channel, but I have
> no experience with fibre channel and don't know about compatible cards
> with linux.
> Our budget isn't quite in the EMC range, but I still figure there is
> something out there that someone on this list might know about.
> All replies appreciated. Thanks in advance!
> 
> Chris
> 

You do understand the machine you're connecting to is pretty important
when talking about those sorts of rates. Needs to have a 64 bit PCI
slot and clocked probably at 66Mhz. Also, one assumes you don't want this
any place but on the local machine because if you want it over a network,
you double your PCI bus load. A 64 bit 33Mhz bus is 264MB/sec. 64 bit/66Mhz
is 528MB/sec. (Theoretically) Might want to decide what machine is capable
of even doing that level in addition to what subsystem. Note the threads
lately on PCI Myrinet performance. They discuss tested performance levels
of various chipsets. Select one of the good ones as a starting point for your
system. Then, go find a card that can sustain that rate. Ultra160 ought
to be able to. I personally would consider whether taking a few large SCSI
disks and striping them with Linux SW raid would do the job. If you're looking
for a canned solution, I'm not aware of one so can't help you there.

Good luck.

Wes
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