RE: To ASM or Not to ASM

Probably should cc: this on oracle-l.  

Regarding performance, several storage vendors (EMC and NetApp come to mind) claim optimal performance by letting the storage array stripe physical spindles inside the array, splitting this striped physical volume into multiple logical volumes, presenting them to the host as multiple LUNs and letting ASM stripe (again) over those logical volumes... hence plaiding. We never got around to testing whether this actually improves performance, instead opting to let ASM do its extent-level striping across separate RAID10 groups used as separate ASM disks. The performance has been good (actually, it's been terrific) but if I could do it all over again, I'd probably try a "plaiding" approach - I can see how this would allow ASM + SAN to improve performance.  

Official recommendations are on OTN in the "ASM" area - EMC and NetApp have published some whitepapers. In practice, I have found that we quickly can glean more information on our own than from vendor contacts.  

We have one fairly mission critical DB running on ASM, size about 200GB (not too big) and we need to be able to hit somewhere in the neighborhood of about 5K IOPS of mixed read/write (including redo), which we're able to do quite easily with ASM managing, I think, 26 x 15K disks. I've been pretty pleased.

From: Amihay Gonen [mailto:AmihayG_at_ectel.com] Sent: Tuesday, July 12, 2005 3:57 PM
To: Murching, Bob
Subject: RE: To ASM or Not to ASM

Hi bob , thanks for the feedback.  

Are the any official recommendations from EMC/NetAPP on using ASM ? Do you have contact information that I can talk with ?  

What do you mean mulipathing across LUNS ? can you give an example ?  

What are the size and I/O requirements from the databases that you have placed on the ASM ?  

From: Murching, Bob [mailto:bob_murching_at_BUDCO.com] Sent: Tue 7/12/2005 7:03 PM
To: Amihay Gonen
Subject: RE: To ASM or Not to ASM

Some quick thoughts -  

We're using ASM in a limited but production capacity. Some observations -  

• it has proven to be extremely stable, at least as of 10.1.0.4 on Solaris 64-bit
• the disk group management really does work
• there is almost no tuning necessary - it works well "out of box"
• lack of multipathing across LUNs is kind of frustrating. Well, very frustrating.
• difficult to move files in and out of ASM volumes. Difficult to "script" although this has been addressed a bit in R2
• performance monitoring interfaces are weak / clumsy / generate questionable data
• everyone (EMC, NetApp, etc.) seems to recommend using ASM stripping on top of SAN/NAS striping (i.e. "plaid") as a best practice... I find this interesting.
• oh... fast, clustered storage for RAC. always nice to have.

I'd appreciate reading any thoughts or additional feedback you receive as well... we're in the same boat, but I chose to roll out ASM for some instances just to "kick the tires"

From: Amihay Gonen [mailto:AmihayG_at_ectel.com] Sent: Tuesday, July 12, 2005 11:53 AM
To: oracle-l_at_freelists.org
Subject: Q:To ASM or Not to ASM

I've some questions on ASM (automatic storage management )  

I've read a lot of materials on this issue , I think ASM is a good concept in simplify the installation & maintenance of oracle database.  

I work in R&D in my organization , and we need to decided if to cooperate ASM instead of some other LVM.  

I build a small list of advantanges and disadvantages on ASM , and some questions . I would like to hear you comments .  

Advantanges:
1. Simply configuration and maintenance. (same layout ,with regard to O/S type . The only change is the numbers of disk per disk group) 2. Reduce extra level of LVM (reduce price , same vendor in all the stack ). 3. Performance (raw device access , striping in extent level )  

disadvantages:
1. New technology . Not wide speared , most IT doesn't have enough knowledge in this area.
2. Backup & recovery must be done using RMAN . 3. Single point of failure - If ASM instance is down ( , I'm not sure about this point).  

My questions are :
1. Do you think that ASM will be acceptable next year as LVM solution for oracle database in big companies ?
2. Do you think that ASM can be fine tuned as you can tune in a file base level installation ?  

Amihay Gonen
DBA  

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