[Gluster-users] Online operations

Anselm Strauss amsibamsi at gmail.com
Mon Nov 15 21:46:13 UTC 2010

But you can not remove a brick without interrupting applications that
access data on that brick, right? The documentation says: "Data residing
on the brick that you are removing will no longer be accessible at the
Gluster mount point." So is there a way of doing a "imbalance" so that
data on the brick to be removed will first be allocated in the
background and online onto other bricks?

What I meant by splitting and merging volumes was motivated by a use
case I often see, that is when you decide that certain data in a folder
needs to be isolated onto a separate volume. This happens e.g. when a
NFS volume needs to be restricted in access only to certain hosts or
when one wants to avoid the interruption of an application by another
one that runs crazy and fills up all space. Often I see that people
first realizing this after the application is already in production or
simply when the requirements change.
For myself I always see this with ZFS. Data sets are really cheap and
easy to do. So I start with one for the whole pool, then later when I
see how the application really works I start to split up and set
different properties (like quota, compression, etc.) for each data set.
But when I do that later on I always have to migrate the data manually
to the new mount point and interrupt the application.
But I guess this is also a problem of the idea of mount points. How do
you move data between mount points without interrupting access to it ...

On 11/14/10 03:59, Craig Carl wrote:
> Anselm - 
> You can remove a brick online, you can't change the type of an existing volume, if you could explain what you what to do with a 'merge' and a 'split' I could give you a better answer, you can 'split' a volume by moving half the data to another volume and 'merge' data by copying all the data from one volume to another, is that what you want to do? 
> Parity based storage in a distributed file system is difficult for several reasons, we are currently investigating some possibilities with erasure coding and will keep everyone up to date on our progress. 
> Thanks, 
> Craig 
> --> 
> Craig Carl 
> Senior Systems Engineer 
> Gluster 
> From: "Anselm Strauss" <amsibamsi at gmail.com> 
> To: gluster-users at gluster.org 
> Sent: Saturday, November 13, 2010 1:56:03 AM 
> Subject: [Gluster-users] Online operations 
> Hi, 
> I have done some testing with glusterfs on the localhost. I was 
> wondering what all operations you can do online with a glusterfs volume. 
> Is it possible to remove a brick and shrink the volume without taking 
> some data offline? Like a pvmove in Linux LVM that moves all data off a 
> disk before you take it offline? 
> Are the following operations possible to do online? 
> - Change between mirroring and striping 
> - Change the mirror or stripe count 
> - Merge two volumes 
> - Split a volume into two 
> Is there a plan for supporting other redundancy levels that mirror, e.g. 
> RAID 5, 6, ...? 
> Thanks for any ideas, 
> Anselm Strauss 
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