[Gluster-devel] [POC] disaster recovery: reconstruct all shards

[Krutika Dhananjay]

The caveats are:

1. A non-existent/missing shard anywhere between offset $SHARD_BLOCK_SIZE
through ceiling ($FILE_SIZE/$SHARD_BLOCK_SIZE)
indicates a hole. When you reconstruct data from a sharded file of this
nature, you need to take care to retain this property.

2. The above is also true for partially filled shards between offset
$SHARD_BLOCK_SIZE through ceiling ($FILE_SIZE/$SHARD_BLOCK_SIZE).
What do I mean by partially filled shards? Shards whose sizes are not equal
to $SHARD_BLOCK_SIZE.

In the above, $FILE_SIZE can be gotten from the
'trusted.glusterfs.shard.file-size' extended attribute on the base file
(the 0th block).

-Krutika

On Mon, Feb 27, 2017 at 1:45 PM, Gandalf Corvotempesta <
gandalf.corvotempesta at gmail.com> wrote:

> Which caveats?
> Anyway, having this recovery tool integrated in gluster could be an
> appreciable plus to guarantee data recovery natively
>
> Il 27 feb 2017 6:02 AM, "Krutika Dhananjay" <kdhananj at redhat.com> ha
> scritto:
>
>> It should be possible to write a script that stitches the different
>> pieces of a single file together
>> (although with a few caveats).
>>
>> -Krutika
>>
>> On Sun, Feb 26, 2017 at 8:52 PM, Gandalf Corvotempesta <
>> gandalf.corvotempesta at gmail.com> wrote:
>>
>>> Would be possible to add a command to use in case of disaster recovery
>>> (where everything is broken) to recreate files from sharding ?
>>>
>>> In example, let's assume a totally down cluster. no trusted pools and
>>> so on but sysadmin knows which hdd is part of any distributed replica:
>>>
>>> hdd1 + hdd2 + hdd3 are distributed and replicated to hdd4 + hdd5 + hdd6
>>>
>>> a CLI could traverse hdd1,hdd2,hdd3 and reconstruct all shards
>>> creating the original, unsharded file.
>>> _______________________________________________
>>> Gluster-devel mailing list
>>> Gluster-devel at gluster.org
>>> http://lists.gluster.org/mailman/listinfo/gluster-devel
>>>
>>
>>
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