Re: multi-owner diskset, database failover

From: Rob Verschoor (rob_at_DO.NOT.SPAM.sypron.nl.REMOVE.THIS.DECOY)
Date: 10/04/04 

Date: Mon, 04 Oct 2004 12:41:47 GMT

Active-active failover is about the same databases.
The setup is this:
- two ASE servers (say, A and B) are running indepently on hardware which an
HA subsystem
- each ASE server has its own databases, but can access the disks on which
the other server's databases are stored
- when one ASE server -say, A- goes down, the OS's HA subsystem initiates a
sequence where the databases from server A are mounted in server B, and the
active user connections to server A are migrated to server B. This is
actually a very fast process (typically seconds rather than minutes) and is
often fully transparant to the users.

There's much more to say about this topic, so I recommend yoou read the HA
manual in the ASE documentation (sybooks.sybase.com/as.html).

HTH,

Rob
-------------------------------------------------------------
Rob Verschoor

Certified Sybase Professional DBA for ASE 12.5/12.0/11.5/11.0
and Replication Server 12.5 / TeamSybase

Author of Sybase books (order online at www.sypron.nl/shop):
"Tips, Tricks & Recipes for Sybase ASE"
"The Complete Sybase Replication Server Quick Reference Guide"
"The Complete Sybase ASE Quick Reference Guide"

mailto:rob@YOUR.SPAM.sypron.nl.NOT.FOR.ME
http://www.sypron.nl
Sypron B.V., P.O.Box 10695, 2501HR Den Haag, The Netherlands
-------------------------------------------------------------

"noone" <noone@noone.org> wrote in message
news:JXJ5d.5607$5O5.3596@news-server.bigpond.net.au...
> Solaris Volume Manager multi-owner diskset, shared disk array.
>
>
> I'm at a lost ( no clustering experience ), so please bear with me:
>
> 1) I could not understand how multi-owner diskset actually work, with 2
> or more noders in a cluster actively reading AND writing to the disks in
> the diskset concurrently. How does this actually work ? Dont you need
> some sort of SCSI reservation ( or diskset's reseveration ) ? I always
> thought only 1 host can ever write to a physical disk.
>
>
> 2) When asking about Sybase's Failover / HA, they have an active-active
> and active-standby setup. Initially, I thought "wow!" active-active. Two
> ( or more ) sybase instances on 2 ( or more ) separate hosts actively
> reading and writing to the same sybase raw devices! But I did not
> actually understood how would that work. Then read about DiskSuite 4.2.1
> diskset documentation ( without reading Solaris9's SVM multi-owner
> diskset yet ), it says that with a diskset can only have one host
> reading / writing from the disks on the diskset at any given time.
>
> Therefore, I then thought that Sybase's active-active is not really what
> I though it was ... now thinking that it was actually "active" on
> different databases ( and therefore different raw devices ). Thus, 2
> sybase instances are running on different hosts, but serving different
> databases.
>
>
> 3) Then I read about Solaris9's SVM multi-owner diskset, which according
> to the docs says allows nodes on the cluster actively reading/ writing
> to disks on the diskset at the same time.... refuelling my initial
> thoughts of Sybase active-active setup.
>
>
> So my questions are:
>
> *) Which of my understanding of active-active is actually correct ?
> Active on the same user database or active on different user databases.
>
> *) To actually make use of active-active on the same database on
> solaris, I presume you would at a minimum need Solaris9, since disksuite
> on Solaris8 does not seem to support multi-owner disksets.
> Am I correct ?
>
>

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