NFS _write_ Performance became horrible overnight

[Igor Chudov <ichudov@gmail.com>]

Hello,

I would like to apologize in advance if, for any reason, my question
is inappropriate for this mailing list. Please let meknow if that is
the case.

This seems to be a very odd problem that I have isolated to NFS.

I have two NFS servers. Server A and server B. They serve unrelated
shares.

Server A is actually two servers using DRBD to stay in sync.

I also have a number of NFS clients.

Both servers worked great up to about last night.

Somehow, NFS writes became extremely slow over Server A, for all
clients, but not for Server B.

I have no idea, yet, what changed, but wanted to ask here if anyone
ever had a similar problem (NFS performance going to shit overnight).

Some data points:

1) From any client, reading files over NFS is fast
2) From any client, writing to NFS on Server A is VERY SLOW
3) From any client, writing to Samba shares on Server A is fast.
4) From any client, writing to NFS on Server B is fast.
5) When logged on to Server A, copying a file from local A filesystem
to itself is fast.

IOW, everything is fast, EXCEPT for NFS writes to server A.

Any ideas what might cause this sudden deterioration of Server A?

Thank you!!!!!!!!!!!

i