On Sat, Sep 05, 2009 at 10:58:20PM -0400, Derek J. Balling spake thusly: > The raw-bandwidth capacity of SATA-II is 3Gbps, or about 300MB/s. > Even if I concede 50% overhead on that, that's still greater than > the capacity of a single GigE.
Right. But no SATA-II disk I have ever owned has come anywhere near saturating that. 3Gbps is pure marketing. > Which is why SANs (from my experience anyway) tend towards > FibreChannel (either 2Gbps or 4Gbps) or multiple Ethernet > connections bonded together via 802.3ad/LACP/etc. protocols (like > you're doing). Which is why I typically bond at least two. > But a single ethernet channel is *definitely* a bottleneck for most > disk access.... Most? Seems pretty unlikely to me. Depends on the workload. Even disk to disk local RAID rebuilds don't do 100MB/s. Have you actually measured how many megabytes per second you are really transferring over your SAN? I bet it isn't nearly as much as you think. I have munin graphs which show that my SAN (running various MySQL, http, email, etc servers on Linux) rarely needs even 100MB/s. And I'm handling hundreds of thousands of emails and tens of thousands of unique IPs/web hits a day. -- Tracy Reed http://tracyreed.org
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