Vladislav Bolkhovitin, on 03/19/2009 08:44 PM wrote:
6. Unexpected result. In case, when all IO threads work in the same IO
context with CFQ increasing RA size *decreases* throughput. I think this
is, because RA requests performed as single big READ requests, while
requests coming from remote clients are much smaller in size (up to
256K), so, when the read by RA data transferred to the remote client on
100MB/s speed, the backstorage media gets rotated a bit, so the next
read request must wait the rotation latency (~0.1ms on 7200RPM).
^^^^^^^^^^^^^^^^^
Oops, it's RP*M*, hence the full rotation latency is in 60 times more,
i.e. 8.3 ms.
Sorry,
Vlad
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