[Ocfs2-users] ASM over OCFS2 vs. Standard locally managed tablespaces

[Karim Alkhayer]

We're using OCFS2 for RAC on top of  SLES9, which we're going to upgrade to
SLES10. Around 10 TB RAID6 multi disk arrays, 5 databases on RAC, and 5
single instances standby for the primary site

 

As there is no AI component in ASM to detect the fast LUNs, and RAC on SLES
requires a shared file system. Therefore, on a set of identical LUNs, in
terms of capacity and speed, ASM should take care of distributing the
balance over LUNs, and OCFS2 is expected to work even better if these LUNs
are placed on several disk groups (arrays)

 

How would this scenario (ASM over OCFS2) work? What are the cons and pros?
Keep in mind that the goal of such a concept is provide performance and
reliability with  the least possible administration

 

Appreciate your thoughts

 

Best regards,

Karim

 

 

From: ocfs2-users-bounces at oss.oracle.com
[mailto:ocfs2-users-bounces at oss.oracle.com] On Behalf Of Luis Freitas
Sent: Monday, February 09, 2009 2:16 PM
To: <ocfs2-users at oss.oracle.com>
Subject: Re: [Ocfs2-users] ASM over OCFS2 vs. Standard locally managed
tablespaces

 


Karim,

   I dont see why run ASM over OCFS2. It seems to be a useless overhead.
Either you run ASM or OCFS2.

   Btw, neither ASM nor OCFS2 are smart enough to detect that some LUNs are
faster than others. ASM expects each diskgroup to be comprised of LUNs of
similar performance in order for it's load balancing algorithms to work.
OCFS2, as far as I know doesnt have this type of management built in.

See:
http://www.oracle.com/technology/products/database/asm/pdf/take%20the%20gues
swork%20out%20of%20db%20tuning%2001-06.pdf
Section: ASM Best practices and principals.

   About the performance, ASM is said to have similar performance to raw
devices in a SAME layout, being tightly integrated to Oracle. OCFS2 has some
overheads that are inherent to a file system, like cache management,
locking, context switching, so it is likely to use more CPU power than ASM.
But I dont remember any specific benchmark comparing those. 

    Also, keep in mind that when you use a filesystem you are using part of
the memory for the filesystem cache. When using RAW or ASM you would need to
allocate this memory to the block buffer in order to compare results.

Regards,
Luis




> Hello All,


>


>


>


> Are there any benchmarks with respect to performance with respect to  


> ASM over OCFS2 vs. standard locally managed tablespaces?


>


> In our environment, data files hosting tables/lobs are stored on a  


> RAID6 disk array with 10K rpm disks, whilst indices are  stored on a  


> different RAID6 disk array with 15K rpm disks.


>


> We?re using oracle managed files for the
 rollback/undo and temporary 


>  tablespaces.


>


> Would ASM over OCFS2 be smart enough to detect the fast LUNs?


>


>


>


> Appreciate your thoughts.


>


>


>


> Best regards,


>


> Karim


>


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