Chan Ching Yu, Patrick
2013-Jun-22 23:50 UTC
Re: Poor Direct-IO Performance with Lustre-2.1.5
Hello! On Jun 22, 2013, at 7:50 PM, Chan Ching Yu, Patrick wrote:> Record Size 1024 KBThis is your problem. DirectIO is synchronous in nature so only as much data as you fit into a single syscall will be in flight at any given moment. In this case you only have 1 RPC in flight. The key to adequately performing DirectIO is to have read/write syscalls with a lot of data. 8*num_stripes is the very minimum, I would think. Even then you likely won''t get cached read/write performance unless you run a very underpowered client that gets choked on memory copies. Bye, Oleg