We should document:
- the correct approach to expand a logical volume that underlies a gluster volume
- when to expand the logical volume vs when to expand the gluster volume by adding a new brick

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Context:

Prashant from GSS contacted me today about the correct approach to expand a logical volume that underlies a gluster volume [1].

As far as I can see we don't have guidance about this in the RHGS docs. This makes sense, but customers do have to consider whether to expand underlying logical volume, or expand the gluster volume, and we should provide some guidance on when to do each, and how to approach.


[1] Our conversation:
‎[10:42] ‎<‎pdhange‎>‎ do you have details of growing brick lvm disk size ?
‎[10:42] ‎<‎pdhange‎>‎ to grow gluster volume
‎[10:42] ‎<‎laubai‎>‎ ah, as in growing the underlying logical volume? it'll be in the RHEL docs, let me locate
‎[10:42] ‎<‎pdhange‎>‎ yes
‎[10:42] ‎<‎pdhange‎>‎ are there any specific restriction with respective gluster ?
‎[10:44] ‎<‎laubai‎>‎ hmm, I'm not sure... I wouldn't think so... maybe just a rebalance afterward? hunting...
‎[10:45] ‎<‎pdhange‎>‎ that's what I think of but not sure
‎[10:46] ‎<‎laubai‎>‎ Okay, growing: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/logical_volume_manager_administration/fsgrow_overview and https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/logical_volume_manager_administration/lv#lv_extend
‎[10:46] ‎<‎pdhange‎>‎ may be rebalancing required only for remove/add brick
‎[10:46] ‎* ‎pdhange‎‎ checking
‎[10:48] ‎<‎pdhange‎>‎ yup, makes sense
‎[10:48] ‎<‎laubai‎>‎ according to some upstream mailing list threads it should be fine to resize the logical volume underlying the gluster volume with POSIX....
‎[10:48] ‎<‎pdhange‎>‎ k
‎[10:48] ‎<‎laubai‎>‎ our docs only really cover expanding the gluster volume rather than the underlying... we should add some clear guidance on this