Extremely slow du

[mohammad kashif <kashif.alig@xxxxxxxxx>]

Hi

I have just moved our 400 TB HPC storage from lustre to gluster. It is part of a research institute and users have very small files to  big files ( few KB to 20GB) . Our setup consists of 5 servers, each with 96TB RAID 6 disks. All servers are connected through 10G ethernet but not all clients.  Gluster volumes are distributed without any replication. There are approximately 80 million files in file system.

I am mounting using glusterfs on  clients.

I have copied everything from lustre to gluster but old file system exist so I can compare.

The problem, I am facing is extremely slow du on even a small directory. Also the time taken is substantially different each time. 

I tried du from same client on  a particular directory twice and got these results.

time du -sh /data/aa/bb/cc
3.7G /data/aa/bb/cc
real 7m29.243s
user 0m1.448s
sys 0m7.067s

time du -sh /data/aa/bb/cc
3.7G      /data/aa/bb/cc
real 16m43.735s
user 0m1.097s
sys 0m5.802s

16m and 7m is too long for a 3.7 G directory. I must mention that the directory contains huge number of files (208736)

but running du on same directory on old data gives this result

time du -sh /olddata/aa/bb/cc
4.0G /olddata/aa/bb/cc
real 3m1.255s
user 0m0.755s
sys 0m38.099s

much better if I run same command again

time du -sh /olddata/aa/bb/cc
4.0G /olddata/aa/bb/cc
real 0m8.309s
user 0m0.313s
sys 0m7.755s

Is there anything I can do to improve this performance? I would also like hear from some one who is running same kind of setup.

Thanks

Kashif

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