NFS Performance – Improving Slow Transfer of Small Files

nfsperformance

I'm using Openfiler 2.3 on an HP ML370 G5, Smart Array P400, SAS disks combined using RAID 1+0.

I set up an NFS share from ext3 partition using Openfiler's web based configuration, and I succeeded to mount the share from another host. Both host are connected using dedicated gigabit link.

Simple benchmark using dd:

 $ dd if=/dev/zero of=outfile bs=1000 count=2000000
 2000000+0 records in
 2000000+0 records out
 2000000000 bytes (2.0 GB) copied, 34.4737 s, 58.0 MB/s

I see it can achieve moderate transfer speed (58.0 MB/s).

But if I copy a directory containing many small files (.php and .jpg, around 1-4 kB per file) of total size ~300 MB, the cp process ends in about 10 minutes.

Is NFS not suitable for small file transfer like above case? Or is there some parameters that must be adjusted?

Best Answer

There are many reasons why transferring many small files will always be slower than transferring a single large file. For a read, the files are more likely to be scattered around the disk, requiring seeks all over the place to get them. As Evan mentioned, there's also metadata involved in the case of NFS (or any other file system for that matter!) which also complicates things.

You can try increasing your rsize and wsize parameters to the NFS mount and see if that will help performance a bit. Also check out this question on tuning NFS for minimum latency as it has a lot of helpful advice that will help in the case of many small file transfers.

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