[CentOS] network copy performance is poor (rsync) - debugging suggestions?

Gordon Messmer
Wed, 28 Jan 2015 23:39:50 -0000

On 01/23/2015 01:44 AM, G?tz Reinicke - IT Koordinator
wrote:
> I do have two centos 6.6 servers. With a "performance optimized"
rsync I
> get an speed of 15 - 20 MB/s

That *is* pretty slow for sustained writes.  Does the same rate hold
true for individual large files as it does for lots of small ones?  What
filesystem are you using on each side?

> rsync -aHAXxv --numeric-ids --progress -e "ssh -T -c arcfour -o
> Compression=no -x"

It's worth noting that -X and -A are going to perform filesystem IO that
you don't see on SMB, because it isn't going to preserve/set ACLs and
extended attributes (IIRC).  So, one possibility is that you're seeing a
difference in rate because you're doing lots of small files and
filesystem operations are relatively slow.

You might drop those two options and see how that affects the rate.  If
you determine that those are the cause of the performance difference,
you can turn them back on, understanding that there's a cost associated
with preserving that data.

> Both servers have plenty of memory and cpu usage looks low.

Define low.  If you're using top and press '1' to expand the CPU
lines,
you'll probably see one cpu with higher "us" percentage, which is
SSH
encrypting the data.  What percentage is that?  Is there a large value
in "sy" or "hi" on any CPU?  Probably not since you see good
rates using
'dd' and smb copies, but I've seen systems where interrupt
processing
was a major bottleneck, so I make it a standard check.