[premise-users] extending downtime today

[Robert Anderson]

The metadata storage problem is proving more difficult to resolve. I hate  
keeping Premise down longer, but it's a lot better than having to say we 
lost all your stored data.

The issue is that the primary metadata server is failing to mirror it's 
data to the secondary. We beleive a full parallel file system check is 
needed, but that fails when the secondary metadata mirror is out of sync. A 
catch 22, that has no simple solution.

The underlying low level file storage currently utilizes a hardware 
mirrored pair of SSD drives. This lowest level storage passes individuall 
file system checks.

To ensure the safety of the stored data we want to get at least one good 
offline copy of the current metadata. That process is going much slower 
than anticipated. Since we have no successful backup of this metadata, we 
have nothing to base a completion estimate on.

Once the backup safety net is in place we need to: reconfigure things to 
remove the secondary metadata mirror, perform the parallel file system 
check, and then add back the secondary meta data sever. Getting a good 
backup requires no users. The parallel file system check and re-mirror 
would be faster without users, but can also be done with normal user workloads.

While we are down we will also try to reconfigure the storage on the idle 
server to avoid this meta data backup issue in the future.
During active use the metadata is always changing, and backups take many 
hours to complete. So we can never able capture a stable backup with active 
users on Premise.  Changing the low level storage to a file system that 
supports snapshots and replication, will provide us with a few viable 
backup options moving forward.

I will send another status update email this evening.

On October 12, 2020 17:17:45 Robert Anderson <rea at sr.unh.edu> wrote:
> There was a filesystem error on Premise /mnt/home.
>
> A filesystem check on the main /mnt/home space needs to complete without 
> active users.
>
> Hopefully the system will be back online later this evening or in the 
> morning if the check takes all night.
>
>
> On Mon, 2020-10-12 at 08:33 -0400, Thomas J. Baker wrote:
>> We lost chilled water this morning and the Premise cluster has been shut 
>> down. The back up chiller appears to be misbehaving as well so no ETA yet 
>> on Premise return to service.
>>
>> Thanks,
>>
>> tjb
>> --
>> =======================================================================
>>> Thomas Baker |
>>> Systems Programmer email:
>>> tjb at unh.edu
>>> |
>>> Research Computing Center office: Morse 206 |
>>> University of New Hampshire voice: (603) 862-4490 |
>>> 213 Morse Hall fax: (603) 862-1761 |
>>> Durham, NH 03824 USA |
>> =======================================================================
>>
>>
>> _______________________________________________
>> premise-users mailing list
>> premise-users at lists.sr.unh.edu
>>
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