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Le 19/05/2016 12:06, Anuradha Talur a écrit :<br>
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cite="mid:294678493.52872421.1463652378984.JavaMail.zimbra@redhat.com"
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----- Original Message -----
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<pre wrap="">From: "Atin Mukherjee" <a class="moz-txt-link-rfc2396E" href="mailto:amukherj@redhat.com"><amukherj@redhat.com></a>
To: "CHEVALIER Pierre" <a class="moz-txt-link-rfc2396E" href="mailto:pchevalier@imajing.org"><pchevalier@imajing.org></a>, <a class="moz-txt-link-abbreviated" href="mailto:gluster-users@gluster.org">gluster-users@gluster.org</a>
Cc: "Pranith Kumar Karampuri" <a class="moz-txt-link-rfc2396E" href="mailto:pkarampu@redhat.com"><pkarampu@redhat.com></a>, "Ravishankar N" <a class="moz-txt-link-rfc2396E" href="mailto:ravishankar@redhat.com"><ravishankar@redhat.com></a>, "Anuradha Talur"
<a class="moz-txt-link-rfc2396E" href="mailto:atalur@redhat.com"><atalur@redhat.com></a>
Sent: Tuesday, May 17, 2016 10:02:55 PM
Subject: Re: [Gluster-users] 2 nodes volume with existing data
On 05/17/2016 01:59 PM, CHEVALIER Pierre wrote:
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<pre wrap="">Hi everyone,
I have found a similar question in the ML but didn't find the answer I
wanted.
My situation is the following :
We have 2 existing data storage unit with 72TB each, with 10TB left.
Currently these storage unit are synced using rsync periodically. We
want to tansform these 2 nodes into glusterfs bricks without loosing any
data or deleting a node.
I was thinking setting up the 2 nodes with glusterfs in replica this way :
1) Rsync server1/brick1 and server2/brick2 content
2) Create the gluster replica and start :
gluster volume create volume1 replica 2 transport tcp server1:/brick1
server2:/brick1
gluster volume start volume1
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<pre wrap="">Gluster heavily depends on extended attributes for its business logic
and hence configuring a brick with existing data means that the extended
attributes would not be set for these files and hence this may not work
as per the expectation.
Given that you have a restriction using another brick, I'd suggest you
to do the following:
1. Delete all the contents of server2/brick as this is a secondary copy
2. Create a plain distributed volume in server2 with server2/brick1
2. Start the volume
3. Mount the volume and then do copy the content from server1/brick1 to
the mount point.
4. Probe server2 into the cluster
5. Perform an add-brick with server1/brick by gluster volume add-brick
<volname> replica 2 <brick name> (Again make sure the content is deleted
first)
6. This should trigger the self heal
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As of now converting a plain distribute volume to distribute replicate is not going to
automatically heal the files. (We are working on a solution for this.)
If you really want to go ahead with this method then I'd recommend you to do the following :
1) Stop I/O on your volume.
2) Add the new brick.
3) Stop and start your gluster volume
4) Trigger lookup on the files from mount point by doing find . | xargs stat on the mount point.
This should trigger heals on the new brick.</pre>
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Hi,<br>
<br>
OK this is good news, I wanted to avoid to have no backup of the
content. <br>
<br>
So after that I mount the new volume as gluster fs and can start I/O
on it ?<br>
<br>
Thanks for these informations.<br>
<br>
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However since the data volume is very high, self heal can take a longer
time to sync and finish.
Also with a two node setup prevention of split brains is not guaranteed.
An arbiter volume or a 3 way replica would be the solution to tackle
this problem.
Since I am not an AFR expert, I'd like to get a sign off from AFR team
(In cc) before you try this out.
~Atin
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Then, should I run a healing process, or stat each files in order to
self heal ?
What happens if there is a slight difference between the 2 nodes,
mathematically if :
server1/brick1= server2/brick1+delta
Will the delta part impact server1, or will it be lost ?
Maybe I worry for nothing, but as these 2 nodes host important data, I
wanted to make sure that eveything is OK.
Thanks for your help !
--
Pierre CHEVALIER
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<div class="moz-signature">-- <br>
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<span style="font-family: Helvetica,Arial,sans-serif;">
Pierre CHEVALIER<br>
</span><span style="font-family: Helvetica,Arial,sans-serif;"></span></small><br>
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