vfast on clusters

[Orjan Petersson]

Hi,
Does it matter (performanswise or other) on which cluster node I activate vfast? (Or on which node I enable e.g. defragment?)

The system is two clustered ES80 running Tru64 5.1 PK5. Except for 2 local disks on each node, the disks are on an EVA5000 shared between the nodes.

Thanks,
Örjan

[Orjan Petersson]

Oops,
> The system is two clustered ES80 running Tru64 5.1 PK5
That should be Tru64 5.1b PK5

[Han Pilmeyer · Accepted solution]

The vFast status for a domain gets recorded in the metadata. The actions are executed on the CFS server.

At least that is what a small experiment showed. And that's what would make sense too.

So it doesn't matter where you give the command, but the activity will be on the node that is the CFS server.

[Orjan Petersson]

Thanks Han!

What triggered my question is that I started to see, on one node, one of the kernel threads use close to 100% CPU (as shown by ps -o pcpu -m -p "kernel-pid"). This started a short time after I activated vfast and enabled defragment.

After playing around with the cfs SERVER attribute for the file systems and deactivating/reactivating vfast on the domains everything seems to be back to normal.

Any known bugs related to vfast in 51b PK5?

[Han Pilmeyer]

PK5 (BL26) should be be pretty much okay.

If you want to make sure, you could load pfm (sysconfig -c pfm) and then run kprofile. If the top routines are in the msfs space, then it's AdvFS.

[Orjan Petersson]

There is definitely something strange going on. During the night the "kernel idle" process on node 1 again started to eat CPU (105%). This happened with vfast running defragment on 3 domains.

After stopping vfast on 2 of the domains everything went back to normal. (CPU usage for "kernel idle" back to 20-25%)

I did run kprofile and there are a couple of "msfs" routines high up in the list. The results from both with and without the problem are in the attached file.

(I will raise a support case through our local support company)

[Han Pilmeyer]

It's supposed to do this when the CPU and disks are idle. Are you saying it was doing this when the system wasn't idle?

[Orjan Petersson]

No the system was not idle.

If the system is supposed to use only "idle" time to run vfast, I would expect the %CPU of the "kernel idle" process to stay the same before and after deactivating vfast.
What happened is that it went from 105% to 25%.

[Han Pilmeyer]

Yes, but wasn't the 25% with one domain active (instead of 3 with 105%)?

[Orjan Petersson]

Yes, the 25% was after I deactivated vfast on 2 domains.

If I understand you correctly, vfast is supposed to use only othewise idle time to do its work. So, the %CPU of "kernel idle" should not change between vfast running on three domains or on a single one, and either the system would be "idle doing nothing" or "idle doing vfast".

Do I miss something here?