[gpfsug-discuss] Mitigating Poor Small-file I/O Performance

Howard, Stewart Jameson sjhoward at iu.edu
Tue May 20 15:17:32 BST 2014

Hi All,

My name is Stewart Howard and I work for Indiana University as an admin on a two-site replicated GPFS cluster.  I'm a new member of this mailing list and this is my first post  :)

Recently, we've discovered that small-file performance on our system is pretty lack-luster.  For comparison, here are some numbers:

1)  When transferring large files (~2 GB), we get outstanding performance and can typically saturate the client's network connection.  We generally see about 490 MB/s over a 10Gb line, which should be about right, given that we lose half of our bandwidth to replication.

2)  When transferring a large number of small files, we get a very poor transfer rate, generally on the order of 2 MB/s, writing from a client node *inside* the GPFS cluster.

I'm wondering if anyone else has experience with similar performance issues and what ended up being the cause/solution.  Also, I would be interested in hearing any general rules-of-thumb that the group has found helpful in balancing performance between large-file and small-file I/O.

We have gathered some diagnostic information while performing various small-file I/O operations, as well as a variety of metadata operations in quick succession.  I'd be happy to share results of the diagnostics, if it would help provide context.

Thank you so much for all of your help!

Stewart Howard
Indiana University

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