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

Andrew Mast andrew.mast.junk at gmail.com
Fri Jun 21 18:07:42 PDT 2013


Very clear, thank you for the explanation, I misunderstood readahead. Yes
the 1gb and 10gb file transfer tests was on par with NFS.

Our use case is typically compiling and find/grep through (30gb) amounts of
source code so it seems we are stuck with small files.


On Fri, Jun 21, 2013 at 3:42 PM, Drokin, Oleg <oleg.drokin at intel.com> wrote:

> Hello!
> 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.
> Bye,
>     Oleg
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