Re: [oracle-l] Re: is this a failover - or ....
- From: "Markus Reger" <reger@xxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Wed, 28 Jan 2004 09:51:38 +0100
thank you for feedback - I just developped/configured it from the scratch =
as I didn't know of any existing systems.=20
<ggg> as regards to thriftyness we are a bank <ggg>
kr MR
>>> cjpengel.dbalert@xxxxxxxxx 01/27/04 20:44 PM >>>
Markus,
You described an almost perfect failover, and far cheaper than RAC.
Actually, we set this up years ath the datacenter of a local government.=20=
They had many applications, and appr. 18 oracle instances running.
Two HP servers, one storage. Half of the databases mounted form one =
server,=20
the other half from the other. In case of a failure, all non-critical =
apps=20
were stopped, and the critical ones were started from the remaining =
server.
I know of a dutch bank, that is setting up their HA systems in the way =
you=20
describe, thus saving from the horrendous costs of RAC. When you don't =
need=20
the scalability, and can afford a few minutes downtime, your're safe. =
They=20
call it PM/RAC, Poor Man's RAC. As a bank, they're always short of =
money,=20
that's why. :-)
There is at least one Single Point of Failure remaining: your storage=20
cabinet. No problem, but take care of proper procedures what to do if =
the=20
storage fails. You can mirror that to another storage cabinet (or SAN, =
NAS,=20
or whatever non-BAARF-banned configuration you can think of (see=20
www.baarf.com)) or consider using Data Guard, one of my favourites ;-).
Regards, Carel-Jan Engel
=3D=3D=3D
If you think education is expensive, try ignorance. (Derek Bok)
=3D=3D=3D
At 06:45 PM 1/27/2004, you wrote:
>we have - amongst others - 2 sun fire v240, each has fibre channel =3D
>adapters and is connected to a storage system. a storage system is a =3D
>system, that makes the connected machine(s) - if correctly configured - =
=3D
>believe, that there is one ( or more ) additional scsi drive(s), that can =
=3D
>be treated like physically built in device(s). in this document i'll call =
=3D
>it vdisk (like HP does).
><gggg>
>(in case you all know it: forgiveness for beeing smart allecky)=3D20
><gggg>
>
>tricky: both of the 2 sun-v-240 can mount both devices, so - in a =3D
>completely stupid and unusable case - both machines have both devices =3D
>mounted in rw. never considered this as a seriously working configuration.=
=3D
>*BUT* if one sun-v-240 is down, the other one can mount it in rw and use =
=3D
>it. this is a working - and not stupid - situation. (admitted: the =3D
>sun-v-240 is not likely to be down, but just for the sake of this now let =
=3D
>us assume) =3D20
>
>consider the scenario described the paragraph before. and now consider =
=3D
>there is an (identical) oracle installation on both machines, correctly =
=3D
>designed (pathes, sysmlinks...), so that both machines can - mutually =3D
>exclusively - mount the device and start the oracle machine (instance) =
and =3D
>mount and open ... the database(s). it works. listeners can be configured.=
=3D
>works too.=3D20
>
>can this be considered a failover scenario???=3D20
>did I possibly overlook some nasty detail???
>
>any input appreciated. (... even rebukes)
>
>assumed: the storage area network (2TB) never really fails - raid 5, .... =
=3D
>and so forth.
>
>kr MR
>
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