[Gluster-users] Increasing replica count from 2 to 3

[Jackie Tung]

Ravi,

Got it thanks.  I’ve kicked this off, it seems be doing OK.

I am a little concerned about a slow creep of memory usage:

* swap (64GB) completed filled up on server_1
* general memory usage creeping up slowly over time.

$ free -m
              total        used        free      shared  buff/cache   available
Mem:         128829       55596         614          53       72618       71783
Swap:         61034       61034           0

Similar issue on server_2, though lower starting memory usage:

The “available” number is slowly going down - at this rate, probably will go to 0 before heal is done.

We are actually running 3.8.6, I’d like to try to pause the heal, upgrade to 3.8.7, and resume.  Is this possible heal suspend/resume possible or advisable?

The upgrade idea came from this on bugzilla (not 100% if it will help my leak):

https://bugzilla.redhat.com/show_bug.cgi?id=1400927 <https://bugzilla.redhat.com/show_bug.cgi?id=1400927>

Even without doing the upgrade, I may need to restart glusterfs-server anyway to reset memory usage.

Thanks,
Jackie

> On Dec 28, 2016, at 9:40 PM, Ravishankar N <ravishankar at redhat.com> wrote:
> 
> On 12/29/2016 10:46 AM, Jackie Tung wrote:
>> Thanks very much for the advice.
>> 
>> Would you mind elaborating on the "no io" recommendation?  It's somewhat hard for me to guarantee this without a long maintenance window.
>> 
>> What is the consequence of having IO at point of add-brick, and for the heal period afterwards?
> 
> Sorry I wasn't clear. Since you're running  16 distribute legs (16x2), a lot of self-heals would be running and there is a chance that clients might experience slowness due to the self-heals. Other than that it should be fine.
> Thanks,
> Ravi
> 
>> 
>> 
>> 
>> On Dec 28, 2016 8:27 PM, "Ravishankar N" <ravishankar at redhat.com <mailto:ravishankar at redhat.com>> wrote:
>> On 12/29/2016 07:30 AM, Jackie Tung wrote:
>>> Version is 3.8.7 on Ubuntu xenial.
>>> 
>>> On Dec 28, 2016 5:56 PM, "Jackie Tung" <jackie at drive.ai <mailto:jackie at drive.ai>> wrote:
>>> If someone has experience to share in this area, i'd be grateful.  I have an existing distributed replicated volume, 2x16.
>>> 
>>> We have a third server ready to go.  Redhat docs say just run add brick replica 3, then run rebalance.
>>> 
>>> The rebalance step feels a bit off to me.  Isn't some kind of heal operation in order rather than rebalance?
>>> 
>>> No additional usable space will be introduced, only replica count increase from 2 to 3.
>> 
>> You don't need to run re-balance for increasing the replica count. Heals should automatically be triggered when you run 'gluster vol add-brick <volname> replica 3 <list of bricks for the 3rd replica>`. It is advisable to do this when there is no I/O happening  on the volume. You can verify that files are getting populated in the newly added bricks post running the command. 
>> 
>> -Ravi
>>> 
>>> Thanks
>>> Jackie
>>> 
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> 


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