[Gluster-users] HA NFS

[Layer7 Consultancy]

Hi Chris,

Thanks for your answer, this was also my understanding on how things
work when using the FUSE client (all storage nodes are described in
the glusterfsd.vol file and thus the client has connection info to
them).

However, when using NFS the documentation states that one should
connect to the 'management IP' and this also seems to be the only
connection information that the client has.
If this management IP is gone due to the server going down, there is
no way the client can know there are multiple other servers who are
also serving the same content, so unless this virtual IP is taken over
by another storage node, the client wouldn't know where to route the
request to.

Can anyone confirm this?

Cheers,
Koen


2010/7/13 Christopher Hawkins <chawkins at bplinux.com>:
> I can offer a little general information. My understanding is this:
>
> It is not like failover with a virtual IP. Instead, the gluster clients connect to all storage servers at the same time. If one of them becomes unavailable, the client can still reach the remaining one(s). Locks are preserved for all remaining nodes. Writes are marked (in the metadata) as having been completed on the remaining nodes, and NOT completed on whatever nodes is down. On access, the file will be healed if the downed node has returned. Or you can force healing of all files when the node comes back, simply by accessing all files with a 'find' command. See seal healing in the wiki for more information on this.
>
> I am not familiar with OpenQRM so I don't know if or how that would have be tweaked for integration.
>
> Chris
>
> ----- "Layer7 Consultancy" <info at layer7.be> wrote:
>
>> Hi all,
>>
>> I am considering the built-in NFS functionality of Gluster to build a
>> virtual server environment. The idea is to have 4 or 5 hosts (KVM or
>> Xen) that all contain around 300GB of 15K rpm SAS storage in a RAID5
>> array. On each of the host servers I would install a VM with the
>> Gluster Platform and expose all of this storage through NFS to my
>> OpenQRM installation, which would then host all the other VM's on the
>> same servers.
>> An alternative idea is to have the storage boxes separate from the VM
>> hosts, but the basic idea stays the same I think.
>>
>> Now from what I understand, the NFS storage that is exposed to the
>> clients is approached through the management IP of the first Gluster
>> Platform server. My biggest question is what exactly happens when the
>> first storage node goes down. Does the platform offer some kind of
>> VRRP setup that fails over the IP to one of the other nodes? Is the
>> lock information preserved and how does this all work internally?
>>
>> Since I would be using KVM or Xen, it would in theory be possible to
>> build the FUSE client on the host servers, though I am still in doubt
>> on how OpenQRM will handle this. When choosing local storage, OpenQRM
>> expects raw disks (I think) and creates LVM groups on these disks in
>> order to allow snapshotting and backups. OpenQRM would also not know
>> this is shared storage.
>>
>> Does anyone have some insight on a setup like this?
>>
>> Best regards,
>> Koen
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