|
Killer,
That confirms some of my suspicion. In my testing I can see requests for 1024 sectors (512K) of data from the hard drive which the AoE client would have to carve up into individual read/write requests that can fit into an AoE packet. At the server, each of these requests would appear as individual read/write requests of the disk so if you followed the optimal packet usage for Ethernet for AoE you would end up with a jumbo frame request for 17 sectors. The initial 1024 sector request at the client would start on an aligned boundary for the first two 4k "sectors" but then have a trailing 512 byte sector request which will cause the next 7 requests to start off unaligned and end aligned... so a 1024 sector request from the host OS will result in only 1 out of 8 requests starting on an aligned boundary. Since the AoE client driver is handling disk requests from
the host OS, the host OS is going to assume certain things about
the disk and try to ensure proper alignment requests. I even
think I've seen that if you have an application that is going to
write to sector 1 that the host will read (or page) in the 4k
chunk starting at sector 0 and then write out the 4k chunk at
sector 0 with the modification of sector 1.
1) What is the test setup
to determine the results of changing the max request size?
2) How does one measure
latency and "responsiveness"?
David |
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