[Gluster-users] rebalance on large filesystems

[Strahil]

Also consider  switching to 'replica 2 arbiter 1' volumes - arbiter can be '192.168.0.3' for the first pair  and '192.168.0.1' for the second.
You will avoid situations with split brain.

Best Regards,
Strahil NikolovOn Oct 1, 2019 19:15, Strahil <hunter86_bg at yahoo.com> wrote:
>
>
> On Oct 1, 2019 15:40, ML <lists at websiteburo.com> wrote:
> >
> > Hi there,
> >
> > I'm looking for the community's opinion on a gluster volume rebalance 
> > I'm hestitating to start :)
> >
> > Here is my config :
> >
> > Volume Name: nas-3
> > Type: Distributed-Replicate
> > Status: Started
> > Number of Bricks: 2 x 2 = 4
> > Transport-type: tcp
> > Bricks:
> > Brick1: 192.168.0.1:/home/nas-3
> > Brick2: 192.168.0.2:/home/nas-3
> > Brick3: 192.168.0.3:/home/nas-3
> > Brick4: 192.168.0.4:/home/nas-3
> > Options Reconfigured:
> > performance.quick-read: off
> > performance.cache-size: 500MB
> > performance.io-thread-count: 32
> > transport.address-family: inet
> > performance.readdir-ahead: on
> >
> > The bricks are constitued of 4 gluster servers version 3.10.12 :
> >
> > 192.168.0.1 + 192.168.0.2 = 2 x 22 TiB (global usage : 86%)
> > 192.168.0.3 + 192.168.0.4 = 2 x 7   TiB (global usage : 40%) (this 2 
> > bricks came 1 year after the 2 first ones, without rebalance after went 
> > live)
> >
> > Actual usage :
> >
> > on 192.168.0.1 + 192.168.0.2 : /home/nas-3 = 2 x 14,5TiB (Items: 49327658)
> > on 192.168.0.3 + 192.168.0.4 : /home/nas-3 = 2 x 2,8TiB (Items: 10343981)
> >
> > I need advice regarding :
> >
> > - Should I rebalance to fill the 2 x 7.2TiB servers ? (I need space on 
> > the 22TiB servers)
>
> I would say - yes.
>
> > - Is rebalance process dividing files based on disk usage for each 
> > connected brick ? (I'm afraid to see my 7.2 TiB servers become full)
> Nah... Gluster is way smarter than that.Still, distribution is calculated via an algorithm which we can easily call hashing.Each brick has a hash range and when a file is not on it's hashed location - you should rebalance.
>
> By the way, this should have been done when you added the new bricks.
>
> For details, check: https://staged-gluster-docs.readthedocs.io/en/release3.7.0beta1/Features/dht/
>
> > - Given the number of files stored, how to get an idea of the time 
> > needed for the rebalance process to be complete ?
>
> You can't estimate that with high accuracy as you got plenty of variables ->  number of files that should be balanced,size of the files that should be balanced, network bandwidth, load on the volume from your clients, speed  of the underlying disks, etc.
>
> It could take a week , maybe less .
>
> > Thank you for reading me & considering answering :))
> >
> > (If there's a gluster consultant you would recommand for these 
> > questions, please let me know)
> >
> > Quentin
> >
> > ________
> >
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> >
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> >
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> >
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>
> Best Regards,
> Strahil Nikolov
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