[ClusterLabs] Antw: Re: principal questions to a two-node cluster

[Ulrich Windl]

Bernd,

I think you must be more clear on what you want: Do you want a load-balanced
active/active setup, or a failover setup? For fencing, I'd go with SBD: sbd
will still use the ProLiants hardware watchdog to reset the machine.

Regards,
Ulrich

>>> "Lentes, Bernd" <bernd.lentes at helmholtz-muenchen.de> schrieb am 20.04.2015
um
19:12 in Nachricht
<15785B7E063D464C86DD482FCAE4EBA501CAC3CA5286 at XCH11.scidom.de>:
> Michael wrote:
>>
>> Am Montag, 20. April 2015, 15:23:28 schrieb Lentes, Bernd:
>> > Hi,
>> >
>> > we'd like to create a two-node cluster for our services (web,
>> > database, virtual machines). We will have two servers and a shared
>> fiberchannel SAN.
>>
>> > What would you do e.g. with the content of the webpages we offer ?
>> Put
>> > them on the SAN so we don't need to synchronize them between the
>> two nodes ?
>>
>> Yes. That seems to be a good idea.
>>
>> > Also the database and the vm's on the SAN ? Which fs would you
>> > recommend for the SAN volumes ? OCFS2 ? Can I mount the same
>> volume on
>> > each node contemporarily ? Or do I have to use the ocfs2 as a resource
>> > managed by pacemaker, so that the volume is only mounted if it is
>> necessary ?
>>
>> In your setup I'd avoid concurrent mounts of the columes on both
>> servers. If you have concurrent mounts, you will have to use a cluster
file
>> system (OCFS2, GFS, ...). These file systems provide locking. But if
>> pacemaker takes care, that the volumes are only mounted on one
>> machine, you can go with a plain file system (ext4, efx).
> 
> I thought ocfs2 would give me a further level of security. If, somehow, 
> although pacemaker takes care, two hosts try to mount concurrently, with 
> ocfs2 nothing would happen. Right ?
> Is there any reason not to use ocfs2 ? E.g. performance, stability ?
> 
> 
>>
>> if you need LVM, you anyway need LVM2 with Distributed Locking
>> (DLM).
> 
> Yes. I will not use LVM. But if I choose ocfs2, I also need DLM. Right ?
> Or is there an advantage of choosing LVM ? Snapshots ? OCFS2 also seems to 
> be able to take snapshots.
> 
>>
>> Please also consider NFSv4 if your SAN box offers it. NFS has file locking
>> included.
> 
> The SAN does not offer NFS.
> 
>>
>> Please do not hesitate to mail to me or to the list, if there are any
other
>> problems.
>>
>> For the databases, you also could consider using a Master/Slave setup.
>> So the data replication does happen on application level and no shared
>> filesystems are needed. pacemaker handles the state (Master / Slave) of
>> the database application. Otherwise the database would need share
>> storage.
>>
>> Please note that you need fencing in ANY case if you have shared
>> storage.
> 
> Yes. I have HP ProLiant servers with ILO cards, and also a configureable 
> (via LAN) power distributor from APC.
> 
>>
>> Greetings,
>>
> 
> Bist Du der Autor von "Clusterbau: Hochverfügbarkeit mit Linux" ? Tolles 
> Buch.
> 
> 
> Bernd
> 
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