Re: Cluster File System Versus ASM for RAC Deployment in Production?... Pros & Cons

Sorry--I forgot to also include that I completely agree with Matt's comments about using ASM + a CFS--especially to support a secondary archivelog destination. I sometimes also use a local (non-shared) filesystem for a secondary archivelog destination if a CFS isn't available. Some customers don't like to add the additional "special" software required to support the CFS in an already-complex environment.

Good comments, Matt.

Dan

• Original Message ---- From: Dan Norris <dannorris_at_dannorris.com> To: Matthew Zito <mzito_at_gridapp.com>; VIVEK_SHARMA_at_infosys.com; oracle-l_at_freelists.org Sent: Thursday, December 6, 2007 8:34:46 AM Subject: Re: Cluster File System Versus ASM for RAC Deployment in Production?... Pros & Cons

>> However, OCFS2 has no capability

 for growing filesystems, creating situations where using OCFS2 for  datafiles means increasing the number of mounts over time, which gets  messy.

That's incorrect. "tunefs.ocfs2 -S /dev/sde1" will grow the FS to the size of the partition where it resides. Just tested it this week:

[root_at_ch-srlxdb01 ~]#
tunefs.ocfs2 -S /dev/sde1  

tunefs.ocfs2 1.2.7  

Changing volume size from
1309649 blocks to 1834541 blocks  

Proceed (y/N): y  

Resized volume  

Wrote Superblock  

• Original Message ---- From: Matthew Zito <mzito_at_gridapp.com> To: dannorris_at_dannorris.com; VIVEK_SHARMA_at_infosys.com; oracle-l_at_freelists.org Sent: Thursday, December 6, 2007 8:29:24 AM Subject: RE: Cluster File System Versus ASM for RAC Deployment in Production?... Pros & Cons

I always recommend using both ASM and a CFS, where appropriate. For  example, on Linux systems, where there is a free, Oracle-supported CFS  (OCFS2), I recommend making a small OCFS2 filesystem (or two) for storage  of OCR and voting files. Then, make the primary datafile/index/log  storage on ASM. Optionally, they can then have a large dump or backup  filesystem that is OCFS2, or NFS - but I always recommend keeping an  archive location outside of ASM, so if the ASM instance won't start up, you  can at least get to your archive logs, and presumably you're doing  backups or a standby database somewhere.

The reason for using both ASM and CFS on Linux is because dealing with  multiple block devices for the various OCR and Voting devices is  annoying and complex, and typically you'll end up wasting a lot of disk space  (i.e. allocating an 8GB lun for a 100MB ocr device). By using a  clustered file system, you can put multiple objects on the one disk, and if  necessary, store other things there. However, OCFS2 has no capability  for growing filesystems, creating situations where using OCFS2 for  datafiles means increasing the number of mounts over time, which gets  messy. ASM solves that problem for you by doing very basic striping.

Thanks,
Matt

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Matthew Zito
Chief Scientist
GridApp Systems
P: 646-452-4090
mzito_at_gridapp.com
http://www.gridapp.com










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