Gluster users - Apr 2018 - Reconstructing files from shards

Il dom 22 apr 2018, 10:46 Alessandro Briosi <ab1 at metalit.com> ha
scritto:
> Imho the easiest path would be to turn off sharding on the volume and
> simply do a copy of the files (to a different directory, or rename and
> then copy i.e.)
>
> This should simply store the files without sharding.
>
If you turn off sharding on a sharded volume with data in it, all sharded
files would be unreadable
>
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So a stock ovirt with gluster install that uses sharding 
A. Can't safely have sharding turned off once files are in use
B. Can't be expanded with additional bricks

Ouch.


On April 22, 2018 5:39:20 AM EDT, Gandalf Corvotempesta
<gandalf.corvotempesta at gmail.com> wrote:
>Il dom 22 apr 2018, 10:46 Alessandro Briosi <ab1 at metalit.com> ha
>scritto:
>
>> Imho the easiest path would be to turn off sharding on the volume and
>> simply do a copy of the files (to a different directory, or rename
>and
>> then copy i.e.)
>>
>> This should simply store the files without sharding.
>>
>
>If you turn off sharding on a sharded volume with data in it, all
>sharded
>files would be unreadable
>
>>
-- 
Sent from my Android device with K-9 Mail. All tyopes are thumb related and
reflect authenticity.
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Il 22/04/2018 11:39, Gandalf Corvotempesta ha scritto:
> Il dom 22 apr 2018, 10:46 Alessandro Briosi <ab1 at metalit.com
> <mailto:ab1 at metalit.com>> ha scritto:
>
>     Imho the easiest path would be to turn off sharding on the volume and
>     simply do a copy of the files (to a different directory, or rename
>     and
>     then copy i.e.)
>
>     This should simply store the files without sharding.
>
>
> If you turn off sharding on a sharded volume with data in it, all
> sharded files would be unreadable
Is it that really so?

I thought that sharding was a extended attribute on the files created
when sharding is enabled.

Turning off sharding on the volume would not turn off sharding on the
files, but on newly created files ...

Anyway if that is so the simplest path would be to crete a new volume
and move/copy files over.

Alessandro
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2018-04-23 9:34 GMT+02:00 Alessandro Briosi <ab1 at
metalit.com>:
> Is it that really so?
yes, i've opened a bug asking developers to block removal of sharding
when volume has data on it or to write a huge warning message
saying that data loss will happen
> I thought that sharding was a extended attribute on the files created when
> sharding is enabled.
>
> Turning off sharding on the volume would not turn off sharding on the
files,
> but on newly created files ...
No, because sharded file are reconstructed on-the-fly based on the
volume's sharding property.
If you disable sharding, gluster knows nothing about the previous
shard configuration, thus won't be able to read
all shards for each file. It will only returns the first shard,
resulting in data-loss or corruption.

2018-04-22 15:10 GMT+02:00 Jim Kinney <jim.kinney at
gmail.com>:
> So a stock ovirt with gluster install that uses sharding
> A. Can't safely have sharding turned off once files are in use
> B. Can't be expanded with additional bricks
If the expansion bug is still unresolved, yes :-)