Gluster users - Nov 2013 - Multiple Volumes (bricks), One Disk

Hi All,

I am interested in some feedback on putting multiple bricks on one physical
disk. Each brick being assigned to a different volume. Here is the scenario:

4 disks per server, 4 servers, 2x2 distribute/replicate

I would prefer to have just one volume but need to do geo-replication on
some of the data (but not all of it). My thought was to use two volumes,
which would allow me to selectively geo-replicate just the data that I need
to, by replicating only one volume.

A couple of questions come to mind:
1) Any implications of doing two bricks for different volumes on one
physical disk?
2) Will the "free space" across each volume still calculate correctly?
IE,
if one volume takes up 2/3 of the total physical disk space, will the
second volume still reflect the correct amount of used space?
3) Am I being stupid/missing something obvious?

Cheers,
Dave
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I would suggest using different partitions for each brick.  We use LVM 
and start off with a relativity small amount allocated space, then grow 
the partitions as needed.  If you were to place 2 bricks on the same 
partition then the free space is not going to show correctly.  Example:

1TB partition 2 bricks on this partition

brick: vol-1-a   using 200GB
brick: vol-2-a   using 300GB.

Both volumes would show that they have ~500GB free, but in reality there 
would be ~500GB that either could use.  I don't know if there would be 
any other issues with putting 2 or more bricks on the same partition, 
but it doesn't seem like a good idea.  I had gluster setup that way when 
I was first testing it, and it seemed to work other than the free space 
issue, but I quickly realized it would be better to separate out the 
bricks on to their own partition.  Using LVM allows you to easily grow 
partitions as needed.

my 2 cents.


On 11/12/13, 9:31 AM, David Gibbons wrote:
> Hi All,
>
> I am interested in some feedback on putting multiple bricks on one 
> physical disk. Each brick being assigned to a different volume. Here 
> is the scenario:
>
> 4 disks per server, 4 servers, 2x2 distribute/replicate
>
> I would prefer to have just one volume but need to do geo-replication 
> on some of the data (but not all of it). My thought was to use two 
> volumes, which would allow me to selectively geo-replicate just the 
> data that I need to, by replicating only one volume.
>
> A couple of questions come to mind:
> 1) Any implications of doing two bricks for different volumes on one 
> physical disk?
> 2) Will the "free space" across each volume still calculate
correctly?
> IE, if one volume takes up 2/3 of the total physical disk space, will 
> the second volume still reflect the correct amount of used space?
> 3) Am I being stupid/missing something obvious?
>
> Cheers,
> Dave
>
>
> _______________________________________________
> Gluster-users mailing list
> Gluster-users at gluster.org
> http://supercolony.gluster.org/mailman/listinfo/gluster-users

-- 
Eric Johnson
713-968-2546
VP of MIS
Internet America
www.internetamerica.com

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