[Gluster-users] Online operations

[Craig Carl]

On 11/15/2010 01:46 PM, Anselm Strauss wrote:
> 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
>> Thanks,
>>
>> Craig
>>
>> -->
>> Craig Carl
>> Senior Systems Engineer
>> Gluster
>>
>> Is there a plan for supporting other redundancy levels that mirror, e.g.
>> RAID 5, 6, ...?
>>
>> Thanks for any ideas,
>> Anselm Strauss
>> _______________________________________________
>> Gluster-users mailing list
>> Gluster-users at gluster.org
>> http://gluster.org/cgi-bin/mailman/listinfo/gluster-users
Anselm -
    I think you may be looking at older documentation, Gluster 3.1 
introduced a migrate command, I think it exactly what you are looking 
for - 
http://www.gluster.com/community/documentation/index.php/Gluster_3.1:_Migrating_Volumes. 
I think you identified the problem with 'spliting' a volume, the volume 
name has to change so there is an application interruption no matter what.


Thanks,

Craig

-->
Craig Carl
Senior Systems Engineer
Gluster