[Gluster-users] how well will this work

Joe Julian joe at julianfamily.org
Fri Dec 28 03:06:08 UTC 2012

I have 3 servers with replica 3 volumes, 4 bricks per server on lvm 
partitions that are placed on each of 4 hard drives, 15 volumes 
resulting in 60 bricks per server. One of my servers is also a kvm host 
running (only) 24 vms.

Each vm image is only 6 gig, enough for the operating system and 
applications and is hosted on one volume. The data for each application 
is hosted on its own GlusterFS volume.

For mysql, I set up my innodb store to use 4 files (I don't do 1 file 
per table), each file distributes to each of the 4 replica subvolumes. 
This balances the load pretty nicely.

I don't really do anything special for anything else, other than the php 
app recommendations I make on my blog (http://joejulian.name) which all 
have nothing to do with the actual filesystem.

The thing that I think some people (even John Mark) miss apply is that 
this is just a tool. You have to engineer a solution using the tools you 
have available. If you feel the positives that GlusterFS provides 
outweigh the negatives, then you will simply have to engineer a solution 
that suits your end goal using this tool. It's not a question of whether 
it works, it's whether you can make it work for your use case.

On 12/27/2012 03:00 PM, Miles Fidelman wrote:
> Ok... now that's diametrically the opposite response from Dan Cyr's of 
> a few minutes ago.
> Can you say just a bit more about your configuration - how many nodes, 
> do you have storage and processing combined or separated, how do you 
> have your drives partitioned, and so forth?
> Thanks,
> Miles
> Joe Julian wrote:
>> Trying to return to the actual question, the way I handle those is to 
>> mount gluster volumes that host the data for those tasks from within 
>> the vm. I've done that successfully since 2.0 with all of those 
>> services.
>> The limitations that others are expressing have as much to do with 
>> limitations placed on their own designs as with their hardware. Sure, 
>> there are other less stable and/or scalable systems that are faster, 
>> but with proper engineering you should be able to build a system that 
>> meets those design requirements.
>> The one piece that wasn't there before but now is in 3.3 is the 
>> "locking and performance problems during disk rebuilds" which is now 
>> done at a much more granular level and I have successfully 
>> self-healed several vm images simultaneously while doing it on all of 
>> them without any measurable delays.
>> Miles Fidelman <mfidelman at meetinghouse.net> wrote:
>>     Joe Julian wrote:
>>         It would probably be better to ask this with end-goal
>>         questions instead of with a unspecified "critical feature"
>>         list and "performance problems".
>>     Ok... I'm running a 2-node cluster that's essentially a mini 
>> cloud stack
>>     - with storage and processing combined on the same boxes. I'm 
>> running a
>>     production VM that hosts a mail server, list server, web server, and
>>     database; another production VM providing a backup server for the
>>     cluster and for a bunch of desktop machines; and several VMs used 
>> for a
>>     variety of development and testing purposes. It's all backed by a
>>     storage stack consisting of linux raid10 -> lvm -> drbd, and uses
>>     pacemaker for high-availability failover of the
>>     production VMs.  It all
>>     performs reasonably well under moderate load (mail flows, web 
>> servers
>>     respond, database transactions complete, without notable user-level
>>     delays; queues don't back up; cpu and io loads stay within 
>> reasonable
>>     bounds).
>>     The goals are to:
>>     - add storage and processing capacity by adding two more nodes - 
>> each
>>     consisting of several CPU cores and 4 disks each
>>     - maintain the flexibility to create/delete/migrate/failover virtual
>>     machines - across 4 nodes instead of 2
>>     - avoid having to play games with pairwise DRBD configurations by 
>> moving
>>     to a clustered filesystem
>>     - in essence, I'm looking to do what Sheepdog purports to do, 
>> except in
>>     a Xen environment
>>     Earlier versions of gluster had reported problems with:
>>     - supporting databases
>>     - supporting VMs
>>     - locking and performance problems during disk rebuilds
>>     - and... most of the gluster documentation implies that it's
>>     preferable
>>     to separate storage nodes from processing nodes
>>     It looks like Gluster 3.2 and 3.3 have addressed some of these 
>> issues,
>>     and I'm trying to get a general read on whether it's worth 
>> putting in
>>     the effort of moving forward with some experimentation, or 
>> whether this
>>     is a non-starter.  Is there anyone out there who's tried to run this
>>     kind of mini-cloud with gluster?  What kind of results have you had?
>>         On 12/26/2012 08:24 PM, Miles Fidelman wrote:
>>             Hi Folks, I find myself trying to expand a 2-node
>>             high-availability cluster from to a 4-node cluster. I'm
>>             running Xen virtualization, and currently using DRBD to
>>             mirror data, and pacemaker to failover cleanly. The thing
>>             is, I'm trying to add 2 nodes to the cluster, and DRBD
>>             doesn't scale. Also, as a function of rackspace limits,
>>             and the hardware at hand, I can't separate storage nodes
>>             from compute nodes - instead, I have to live with 4 nodes,
>>             each with 4 large drives (but also w/ 4 gigE ports per
>>             server). The obvious thought is to use Gluster to assemble
>>             all the drives into one large storage pool, with
>>             replication. But.. last time I looked at this (6 months or
>>             so back), it looked like some of the critical features
>>             were brand new, and performance seemed to be a problem in
>>             the configuration I'm thinking of. Which leads me to my
>>             question: Has the situation improved to the point that I
>>             can use Gluster this way? Thanks very much, Miles Fidelman
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