[Lustre-discuss] Slow Copy (Small Files) 1 RPC In Flight?

Drokin, Oleg oleg.drokin at intel.com
Fri Jun 21 15:42:25 PDT 2013


On Jun 21, 2013, at 5:42 PM, Andrew Mast wrote:

> Hello, I am new to Lustre and wanted to run a small simple small copy test between 2 virtual machines from MDT/OST server to client's local disk.

> I realize small file performance is never fast, but this seems particularly slow considering the data is all buffered in memory with little to no disk activity.
> RPC stats on the client shows only 1 RPC in flight at a time. max inflight is set to 64. Is that expected behavior for a copy?

Well, it seems you are reading from Lustre. Small files too.
So Lustre reads a single file at a time (I assume you copy with somehing like cp - single threadedly), readahead does not come into play because file size
is smaller than 1 RPC.
So before we are done with a single file, we cannot guess there'd be another request to the next file. That's why you have only one RPC in flight.

Also Lustre metadata protocol is somewhat more heavy than NFS, which would explain why it's slower than NFS.
Situation should improve once you start trying bigger files.


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