[Gluster-users] Recovering from remove-brick where shards did not rebalance

[Anthony Hoppe]

I've been playing with re-adding the bricks and here is some interesting behavior. 

When I try to force add the bricks to the volume while it's running, I get complaints about one of the bricks already being a member of a volume. If I stop the volume, I can then force-add the bricks. However, the volume won't start without force. Once the volume is force started, all of the bricks remain offline. 

I feel like I'm close...but not quite there... 

> From: "anthony" <anthony at vofr.net>
> To: "Strahil Nikolov" <hunter86_bg at yahoo.com>
> Cc: "gluster-users" <gluster-users at gluster.org>
> Sent: Tuesday, September 7, 2021 7:45:44 AM
> Subject: Re: [Gluster-users] Recovering from remove-brick where shards did not
> rebalance

> I was contemplating these options, actually, but not finding anything in my
> research showing someone had tried either before gave me pause.

> One thing I wasn't sure about when doing a force add-brick was if gluster would
> wipe the existing data from the added bricks. Sounds like that may not be the
> case?

> With regards to concatenating the main file + shards, how would I go about
> identifying the shards that pair with the main file? I see the shards have
> sequence numbers, but I'm not sure how to match the identifier to the main
> file.

> Thanks!!

>> From: "Strahil Nikolov" <hunter86_bg at yahoo.com>
>> To: "anthony" <anthony at vofr.net>, "gluster-users" <gluster-users at gluster.org>
>> Sent: Tuesday, September 7, 2021 6:02:36 AM
>> Subject: Re: [Gluster-users] Recovering from remove-brick where shards did not
>> rebalance

>> The data should be recoverable by concatenating the main file with all shards.
>> Then you can copy the data back via the FUSE mount point.

>> I think that some users reported that add-brick with the force option allows to
>> 'undo' the situation and 're-add' the data, but I have never tried that and I
>> cannot guarantee that it will even work.

>> The simplest way is to recover from a recent backup , but sometimes this leads
>> to a data loss.

>> Best Regards,
>> Strahil Nikolov

>>> On Tue, Sep 7, 2021 at 9:29, Anthony Hoppe
>>> <anthony at vofr.net> wrote:
>>> Hello,

>>> I did a bad thing and did a remove-brick on a set of bricks in a
>>> distributed-replicate volume where rebalancing did not successfully rebalance
>>> all files. In sleuthing around the various bricks on the 3 node pool, it
>>> appears that a number of the files within the volume may have been stored as
>>> shards. With that, I'm unsure how to proceed with recovery.

>>> Is it possible to re-add the removed bricks somehow and then do a heal? Or is
>>> there a way to recover data from shards somehow?

>>> Thanks!
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