On 05/01/2017 02:42 PM, Pranith Kumar Karampuri wrote:
On Tue, May 2, 2017 at 12:07 AM, Shyam <srangana@xxxxxxxxxx
<mailto:srangana@xxxxxxxxxx>> wrote:
On 05/01/2017 02:23 PM, Pranith Kumar Karampuri wrote:
On Mon, May 1, 2017 at 11:43 PM, Shyam <srangana@xxxxxxxxxx
<mailto:srangana@xxxxxxxxxx>
<mailto:srangana@xxxxxxxxxx <mailto:srangana@xxxxxxxxxx>>> wrote:
On 05/01/2017 02:00 PM, Pranith Kumar Karampuri wrote:
Splitting the bricks need not be a post factum
decision, we can
start with larger brick counts, on a given node/disk
count, and
hence spread these bricks to newer nodes/bricks as
they are
added.
Let's say we have 1 disk, we format it with say XFS and that
becomes a
brick at the moment. Just curious, what will be the
relationship
between
brick to disk in this case(If we leave out LVM for this
example)?
I would assume the relation is brick to provided FS
directory (not
brick to disk, we do not control that at the moment, other than
providing best practices around the same).
Hmmm... as per my understanding, if we do this then 'df' I guess
will
report wrong values? available-size/free-size etc will be
counted more
than once?
This is true even today, if anyone uses 2 bricks from the same mount.
That is the reason why documentation is the way it is as far as I can
remember.
I forgot a converse though, we could take a disk and partition it
(LVM thinp volumes) and use each of those partitions as bricks,
avoiding the problem of df double counting. Further thinp will help
us expand available space to other bricks on the same disk, as we
destroy older bricks or create new ones to accommodate the moving
pieces (needs more careful thought though, but for sure is a
nightmare without thinp).
I am not so much a fan of large number of thinp partitions, so as
long as that is reasonably in control, we can possibly still use it.
The big advantage though is, we nuke a thinp volume when the brick
that uses that partition, moves out of that disk, and we get the
space back, rather than having or to something akin to rm -rf on the
backend to reclaim space.
Other way to achieve the same is to leverage the quota functionality of
counting how much size is used under a directory.
Yes, I think this is the direction to solve the 2 bricks on a single FS
as well. Also, IMO, the weight of accounting at each directory level
that quota brings in seems/is heavyweight to solve just *this* problem.
Today, gluster takes in a directory on host as a brick, and
assuming
we retain that, we would need to split this into multiple
sub-dirs
and use each sub-dir as a brick internally.
All these sub-dirs thus created are part of the same volume
(due to
our current snapshot mapping requirements).
--
Pranith
--
Pranith
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