ASM questions

[bhatia333]

Hi All,
I had a couple of ASM questions.
1) Does ASM really readuce the storage requirements for a database? What I mean to ask is...that is it true that if your db is 100gb under lets say ASSM. If you convert you db to ASM, will it reduce it to lets say 85Gb?
2) Does ASM automatically de-fragment/coelesce your tablespaces/tables?
3) Are there any benchmarks for ASM vs ASSM as far as performance and storage optimization is concerned? If no benchmarks, what has been the experience of people using ASM on PROD enviorments.

Thanks in advance

[hrishy]

1)No
Actually its other way around it wastes some space to acheive high concurrency
2)ASM does not .its more like a volume manager nothing to do with fragmentation
c)You cannot compare ASM with ASSM
ASM performance is same as raw not any faster


If your database size is 10Tb + then the default allocation unit size may need to be tweaked.
Rebalancing operation with large data takes time (this is no longer an issue with 11g )

If you keep files in ASM 10g then all file acesses has to be done through RMAN.
11g has the cp command which is quite hand.

Some companies people are reluctant to keep backups under ASM as in single instance databases ASM is a single point of failure and they are more comfortable keeping archivelogs and backups outside ASM


regards
Hrishy