Incredible slow performance with noac option

Incredible slow performance with noac option

[Markus Grell]

Greetings!

We're observing a very strange (?) behavior when doing some simple NFS tests:

As soon as we add the nfs mount option 'noac' or 'actimeo=0', NFS
performance dramatically drops from say 100 MB/s to 2.5 MB/s.
I searched archives a little bit and read that this option might have a
"slight performance impact", but what we observe is far away from being
"slight"...

What we tested:

Fresh NFS server using Ubuntu 14.04 LTS
Fresh NFS server using RedHat Enterprise 6.4

Ubuntu 12.04 client
Redhat Enterprise 6.4 Client
Oracle 5.7 Client

Content of /etc/exports:

/shared *(rw,async,no_wdelay,insecure_locks,no_root_squash,no_subtree_check)


Mount options:
mount -t nfs -o actimeo=0,tcp,vers=3 nfsserver:/shared /mnt/

The mounted /mnt directory only contains a single file.

'Tests' are done using simple "dd if=/mnt/largefile of=/dev/null"

Output of 'nfsstat -c':

Client rpc stats:
calls      retrans    authrefrsh
1171668    0          1171668

Client nfs v3:
null         getattr      setattr      lookup       access       readlink
0         0% 1159569  98% 0         0% 1         0% 17        0% 0         0%
read         write        create       mkdir        symlink      mknod
12055     1% 0         0% 0         0% 0         0% 0         0% 0         0%
remove       rmdir        rename       link         readdir      readdirplus
0         0% 0         0% 0         0% 0         0% 0         0% 2         0%
fsstat       fsinfo       pathconf     commit
0         0% 6         0% 3         0% 0         0%


Output of 'nfsstat -s'

Server rpc stats:
calls      badcalls   badclnt    badauth    xdrcall
1265267    0          0          0          0

Server nfs v3:
null         getattr      setattr      lookup       access       readlink
8         0% 1251701  98% 0         0% 1         0% 23        0% 0         0%
read         write        create       mkdir        symlink      mknod
13510     1% 0         0% 0         0% 0         0% 0         0% 0         0%
remove       rmdir        rename       link         readdir      readdirplus
0         0% 0         0% 0         0% 0         0% 0         0% 3         0%
fsstat       fsinfo       pathconf     commit
0         0% 8         0% 3         0% 0         0%


Any explanation for this? What did I miss? what am I doing wrong?

I wouldn't use this option but unfortunately its required for Oracle RAC
over NFS...

Thanks for any help
Markus