[Gluster-users] Expanding brick size in glusterfs 3.7.11

[Pascal Suter]

I may add to that that i have expanded linux filesystems (xfs and ext4) 
both via LVM and some by adding disks to a hardware raid. from the OS 
point of view it does not make a difference, the procedure once the 
block device on which the filesytem resides is expanded is prettymuch 
the same and so far always worked like a charm.

one word of caution though: i've just recently had a case with a raid 6 
across 12 disks (1TB, a 5 year old RAID array) where during a planned 
power outage a disk failed, when turnging the storage back on, a second 
failed right after that and the third failed during rebuild. luckily 
this was a retired server used for backup only, so no harm done.. but 
this just shows us, that under the "ritght" circumstances, multi disk 
failures are possible. the more disks you have in your raidset the 
higher the chance of a disk failure.. by doubling the amount of disks in 
your raidset you double the chance of a disk failure and therefore a 
double or tripple disk failure as well.

long story short.. i'd consider creating a second raid acorss your 12 
new disks and adding this as a second brick to gluster storage.. that's 
what gluster's for after all .. to scale your storage :) in the case of 
raid 6 you will loose the capacity of two disks but you will gain alot 
in terms of redundancy and dataprotection.

also you will not have the performance impact of the raid expansion.. 
this is usually a rather long process which will eat a lot of your 
performance while it's ongoing.

of course, if you have mirrored bricks, that's a different story, but i 
assume you don't.

cheers
Pascal

On 26.04.19 05:35, Jim Kinney wrote:
> I've expanded bricks using lvm and there was no problems at all with 
> gluster seeing the change. The expansion was performed basically 
> simultaneously on both existing bricks of a replica. I would expect 
> the raid expansion to behave similarly.
>
> On April 25, 2019 9:05:45 PM EDT, Pat Haley <phaley at mit.edu> wrote:
>
>     Hi,
>
>     Last summer we added a new brick to our gluster volume (running
>     glusterfs 3.7.11).  The new brick was a new server with with 12 of 24
>     disk bays filled (we couldn't afford to fill them all at the time).
>     These 12 disks are managed in a hardware RAID-6.  We have recently been
>     able to purchase another 12 disks.  We would like to just add these new
>     disks to the existing hardware RAID and thus expand the size of the
>     brick.  If we can successfully add them to the hardware RAID like this,
>     will gluster have any problems with the expanded brick size?
>
>     -- 
>     ------------------------------------------------------------------------
>     Pat Haley                          Email:  phaley at mit.edu
>     Center for Ocean Engineering       Phone:  (617) 253-6824
>     Dept. of Mechanical Engineering    Fax:    (617) 253-8125
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>     77 Massachusetts Avenue
>     Cambridge, MA  02139-4301
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