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Re: [dm-devel] dm-multipath has great throughput but we'd like more!

The system bus isn't a limiting factor is it? 64-bit PCI-X will get 8.5 GB/s (plenty), but 32-bit PCI 33MHz got 133MB/s.

Can your disks sustain that much bandwidth? 10 striped drives might get better than 200MB/s if done right, I suppose.

Don't the switches run at 2 Gbits/s? 2 Gbits/s / 10 (throw in 2 bits for protocol) ~= 200MB/s.

Could be a bunch of reasons...


On May 18, 2006, at 2:05 AM, Bob Gautier wrote:

Yesterday my client was testing of multipath load balancing and failover
on a system running ext3 on a logical volume which comprises about ten
SAN LUNs all reached using multipath in multibus mode over two QL2340

On the one hand, the client is very impressed: running bonnie++
(inspired by Ronan's GFS v VxFS example) we get just over 200Mbyte/s
over the two HBAs, and when we pull a link we get about 120MByte/s.

The throughput and failover response times are better than the client
has ever seen, but we're wondering why we are not seeing higher
throughput per-HBA -- the QL2340 datasheet says it should manage
200Mbyte/s and all switches etc. run at 2GBps.

Any ideas?

Bob Gautier
+44 7921 700996

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