Re: Latest recommendation for asmlib + number of LUNs
- From: Frits Hoogland <frits.hoogland@xxxxxxxxx>
- To: Chris.Stephens@xxxxxxx
- Date: Thu, 15 Aug 2013 14:45:38 +0200
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Please mind asmlib is not available from the public yum server, which =
means updating from there will not update asmlib, meaning asmlib is gone =
if there's a new kernel.
Frits Hoogland
http://fritshoogland.wordpress.com
frits.hoogland@xxxxxxxxx
+31 6 53569942
On Aug 15, 2013, at 2:29 PM, "Stephens, Chris" <Chris.Stephens@xxxxxxx> =
wrote:
> I forgot to mention that we will be using the UEK version of Oracle =
Linux so <I think> the patching is a non-issue.
> Thanks for the links and input from everyone.
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> From: Niall Litchfield [mailto:niall.litchfield@xxxxxxxxx]
> Sent: Thursday, August 15, 2013 5:15 AM
> To: Stephens, Chris
> Cc: oracle-l@xxxxxxxxxxxxx
> Subject: Re: Latest recommendation for asmlib + number of LUNs
>=20
> As you say you'll encounter at least 2 different opinions. I fall into =
the "don't think its worth it" camp, so bear that in mind in what =
follows. We also use it exclusively here for our RAC systems - haven't =
got that standard rewritten as yet :)
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> Technically in 11.x asmlib only provides 2 features, both of which I =
would argue are available without it.
>=20
> 1) it provides an exclusive I/O interface to the device
> 2) it labels the disk so that there is persistent naming for the =
device.
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> That's it. It's worth remembering that ASMLIB was born in 2004 when =
async i/o and persistent device naming on Linux platforms was, errm, =
deficient. Those conditions just aren't true today. Disk labelling and =
aliasing is built into both multipath and udev on Linux and works =
perfectly well to ensure that Oracle always finds the same devices at =
the same name. In addition ASMLIB consists both of a userland and kernel =
module, consequently if you patch the O/S kernel - say for security =
reasons - then you *will* have to update asmlib each and every time as =
well. In many cases the *you* that has to do this will be your sys admin =
team, in the case of base O/S packages this shouldn't be an issue. In =
addition as of RHEL/OEL 6 asmlib is pre-compiled only for the =
Unbreakable Enterprise Kernel supplied by Oracle, you should probably be =
using this to be honest, but many people won't be. For these reasons I =
see asmlib as an extra layer requiring maintenance and providing no =
added value.
>=20
> Definitely read https://blogs.oracle.com/wim/entry/asmlib for a =
definitive background. Now Oracle could, and indeed to some extent (on =
Oracle hardware) has enhanced asmlib to provide further features - see =
http://www.scaleabilities.co.uk/2013/02/07/diagnosing-asmlib/ for an =
example.
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> On Wed, Aug 14, 2013 at 8:34 PM, Stephens, Chris =
<Chris.Stephens@xxxxxxx<mailto:Chris.Stephens@xxxxxxx>> wrote:
> I'm venturing into the land of Oracle RAC for the first time and will =
be installing an 11.2.0.3 2-Node cluster from scratch. The storage will =
be allocated from a Dell Compellent (not sure if that's relevant to my =
question or not).
> The official documentation recommends the use of ASMLib but I seem to =
remember a lot of folks on here thinking that was a bad idea or at least =
not a no brainer.
>=20
> What's the current recommendation / bestest idea on ASMLib use?
>=20
> Also, any recommendation on the number of LUN's to start off with for =
each disk group? (+data, +fra) Oracle recommends a minimum of 4 but I'm =
not sure how they arrived at that number or whether more would be =
advantageous. That's probably an "it depends" question so what info do =
I need to make that determination?
>=20
> Thanks,
> Chris
>=20
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> Niall Litchfield
> Oracle DBA
> http://www.orawin.info
>=20
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