[Gluster-users] Need help in understanding volume heal-info behavior

[Chalcogen]

Thank you very much!

On Monday 28 April 2014 07:41 AM, Ravishankar N wrote:
> On 04/28/2014 01:30 AM, Chalcogen wrote:
>> Hi everyone,
>>
>> I have trouble understanding the following behavior:
>>
>> Suppose I have a replica 2 volume 'testvol' on two servers, server1 
>> and server2, composed of server1:/bricks/testvol/brick and 
>> server2:/bricks/testvol/brick. Also, suppose it contains a good 
>> number of files.
>>
>> Now, assume I remove one of the two bricks, as:
>>
>> root at server1~# gluster volume remove-brick testvol replica 1 
>> server1:/bricks/testvol/brick
>>
>> Now, I unmount and delete the logical volume supporting the brick and 
>> then recreate it (with a different size), and mount it the same way 
>> as it was mounted before (at /brick/testvol/). Then, I re-add it as:
>>
>> root at server1~# gluster volume add-brick testvol replica 2 
>> server1:/bricks/testvol/brick
>>
>> I observe that the brick on server1 does not contain any of the data 
>> that was in the volume.
>>
>> root at server1~# ls /bricks/testvol/brick
>> root at server1~#
>>
>> This is all right by me, since glusterfs needs some time to discover 
>> and sync files that are absent on the brick of server1. In fact, if I 
>> leave the setup undisturbed for 15 minutes to half an hour, I find 
>> that all data appears within the brick of server1, just as you would 
>> expect. Also, if I wish to speed up the process, I simply do a ls -Ra 
>> on the directory where the volume is mounted, and all files sync onto 
>> server1's brick. This is also very much as expected.
>>
>> However, during the period where data on server1's brick is not 
>> available, if you query the heal info for the volume, gluster cli 
>> reports that 'Number of entries' is '0', and that too all of 'info', 
>> 'heal-failed', and 'split-brain'. This is what becomes a bit of a 
>> trouble for me. Fact is, we are attempting to automate the monitoring 
>> of our glusterfs volumes, and we depend upon heal info alone to 
>> decide whether data on server1 and server2 are in sync.
>>
>> Could somebody, therefore, help me with the following questions?
>> a) Which files exactly show up in heal info?
> The files which are healed either by the self-heal daemon or by the 
> gluster heal commands.
>> b) What exactly should I look to monitor if we are to ascertain that 
>> data on our servers are in sync?
>>
> After adding a new replica brick, you need to run a full heal (gluster 
> volume heal <vol-name> full). Then the results will show up in the 
> heal info output.
>> Thanks a lot for your responses!
>>
>> Anirban
>>
>> P.s. I am using glusterfs 3.4.2 over linux kernel version 2.6.34.
>>
>>
>>
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>

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