[gpfsug-discuss] correct way of taking IO server down for maintenance

[Damir Krstic]

Hi Jan,

I am sorry if my post sounded accusatory - I did not mean it that way. We
had a very frustrating experience trying to change recoverygroup yesterday
morning. I've read the manual you have linked and indeed, you have outlined
the correct procedure.

I am left wondering why the level 2 gpfs support instructed us not to do
that in the future. Their support instructions are contradicting what's in
the manual. We are running now with the --active recovery group in place
and will change it permanently back to the default setting early in the new
year.

Anyway, thanks for your help.

Damir

On Tue, Dec 20, 2016 at 1:36 PM Jan-Frode Myklebust <janfrode at tanso.net>
wrote:

> I'm sorry for your trouble, but those 4 steps you got from IBM support
> does not seem correct. IBM support might not always realize that it's an
> ESS, and not plain GPFS... If you take down an ESS IO-node without moving
> its RG to the other node using "--servers othernode,thisnode", or by using
> --active (which I've never used), you'll take down the whole recoverygroup
> and need to suffer an uncontrolled failover. Such an uncontrolled failover
> takes a few minutes of filesystem hang, while a controlled failover should
> not hang the system.
>
> I don't see why it's a problem that you now have an IO server that is
> owning both recoverygroups. Once your maintenance of the first IO servers
> is done, I would just revert the --servers order of that recovergroup, and
> it should move back.
>
> The procedure to move RGs around during IO node maintenance is documented
> on page 10 the quick deployment guide (step 1-3):
>
>
> http://www.ibm.com/support/knowledgecenter/en/SSYSP8_4.5.0/c2785801.pdf?view=kc
>
>
>   -jf
>
>
> On Tue, Dec 20, 2016 at 6:19 PM, Damir Krstic <damir.krstic at gmail.com>
> wrote:
>
> For sake of everyone else on this listserv, I'll highlight the appropriate
> procedure here. It turns out, changing recovery group on an active system
> is not recommended by IBM. We tried following Jan's recommendation this
> morning, and the system became unresponsive for about 30 minutes. It only
> became responsive (and recovery group change finished) after we killed
> couple of processes (ssh and scp) going to couple of clients.
>
> I got a Sev. 1 with IBM opened and they tell me that appropriate steps for
> IO maintenance are as follows:
>
> 1. change cluster managers to system that will stay up (mmlsmgr - mmchmgr)
> 2. unmount gpfs on io node that is going down
> 3. shutdown gpfs on io node that is going down
> 4. shutdown os
>
> That's it - recovery groups should not be changed. If there is a need to
> change recovery group, use --active option (not permanent change).
>
> We are now stuck in situation that io2 server is owner of both recovery
> groups. The way IBM tells us to fix this is to unmount the filesystem on
> all clients and change recovery groups then. We can't do it now and will
> have to schedule maintenance sometime in 2017. For now, we have switched
> recovery groups using --active flag and things (filesystem performance)
> seems to be OK. Load average on both io servers is quite high (250avg) and
> does not seem to be going down.
>
> I really wish that maintenance procedures were documented somewhere on IBM
> website. This experience this morning has really shaken my confidence in
> ESS.
>
> Damir
>
> On Mon, Dec 19, 2016 at 9:53 AM Jan-Frode Myklebust <janfrode at tanso.net>
> wrote:
>
>
> Move its recoverygrops to the other node by putting the other node as
> primary server for it:
>
> mmchrecoverygroup rgname --servers otherServer,thisServer
>
> And verify that it's now active on the other node by "mmlsrecoverygroup
> rgname -L".
>
> Move away any filesystem managers or cluster manager role if that's active
> on it. Check with mmlsmgr, move with mmchmgr/mmchmgr -c.
>
> Then  you can run mmshutdown on it (assuming you also have enough quorum
> nodes in the remaining cluster).
>
>
>   -jf
>
> man. 19. des. 2016 kl. 15.53 skrev Damir Krstic <damir.krstic at gmail.com>:
>
> We have a single ESS GL6 system running GPFS 4.2.0-1. Last night one of
> the IO servers phoned home with memory error. IBM is coming out today to
> replace the faulty DIMM.
>
> What is the correct way of taking this system out for maintenance?
>
> Before ESS we had a large GPFS 3.5 installation with 14 IO servers. When
> we needed to do maintenance on the old system, we would migrate manager
> role and also move primary and secondary server roles if one of those
> systems had to be taken down.
>
> With ESS and resource pool manager roles etc. is there a correct way of
> shutting down one of the IO serves for maintenance?
>
> Thanks,
> Damir
>
>
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