Dne 10.09.2020 v 17:40 John Stoffel napsal(a):
So why not run the backend storage on the Netapp, and just keep the
indexes and such local to the system? I've run Netapps for many years
and they work really well. And then you'd get automatic backups using
schedule snapshots.
Keep the index files local on disk/SSDs and put the maildirs out to
NFSv3 volume(s) on the Netapp(s). Should do wonders. And you'll stop
needing to do rsync at night.
Miloslav> It's the option we have in minds. As you wrote, NetApp is very solid.
Miloslav> The main reason for local storage is, that IMAP server is completely
Miloslav> isolated from network. But maybe one day will use it.
It's not completely isolated, it can rsync data to another host that
has access to the Netapp. *grin*
:o)
Miloslav> Unfortunately, to quickly fix the problem and make server
Miloslav> usable again, we already added SSD and moved indexes on
Miloslav> it. So we have no measurements in old state.
That's ok, if it's better, then its better. How is the load now?
Looking at the output of 'iostat -x 30' might be a good thing.
Load is between 1 and 2. We can live with that for now.
Miloslav> Situation is better, but I guess, problem still exists. I
Miloslav> takes some time to load be growing. We will see.
Hmm... how did you setup the new indexes volume? Did you just use
btrfs again? Did you mirror your SSDs as well?
Yes. Just two SSD into free slots, propagate them as two RAID-0 into OS
and btrfs RAID-1.
It is a nasty, I know, but without outage. It is a just quick attempt to
improve the situation. Our next plan is to buy more controllers,
schedule an outage on weekend and do it properly.
Do the indexes fill the SSD, or is there 20-30% free space? When an
SSD gets fragmented, it's performance can drop quite a bit. Did you
put the SSDs onto a seperate controller? Probably not. So now you've
just increased the load on the single controller, when you really
should be spreading it out more to improve things.
SSD are almost empty, 2.4GB of 93GB is used after 'doveadm index' on all
mailboxes.
Another possible hack would be to move some stuff to a RAM disk,
assuming your server is on a UPS/Generator incase of power loss. But
that's an unsafe hack.
Also, do you have quotas turned on? That's a performance hit for
sure.
No, we are running without quotas.
Miloslav> Thank you for the fio tip. Definetly I'll try that.
It's a good way to test and measure how the system will react.
Unfortunately, you will need to do your testing outside of normal work
hours so as to not impact your users too much.
Good luck! Please post some numbers if you get them. If you see
only a few disks are 75% or more busy, then *maybe* you have a bad
disk in the system, and moving off that disk or replacing it might
help. Again, hard to know.
Rebalancing btrfs might also help, especially now that you've moved
the indexes off that volume.
John
Thank you
Milo
