Re: Question on ASM LUN size and adding datafiles
- From: Nuno Souto <dbvision@xxxxxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Sun, 21 Nov 2010 20:28:37 +1100
Riyaj Shamsudeen wrote,on my timestamp of 21/11/2010 6:27 AM:
1. That's right, don't mix lun sizes. Extents are moved from the existing
luns to the new new luns during rebalance operations. ASM will try to keep same
number of extents in every LUN. So, if you mix 90 GB and 60GB luns, if you run
out of space in 60GB luns ( even when there is free space in 90GB luns! ) you
can run in to free space errors. I just had a client issue where the admins
decreased new luns size to 50GB from 200GB original LUN sizes causing ASM
errors.
Lovely... Is this documented anywhere?
2. If you know how much you need, it is better to allocate ahead of time.
Autoextending has *some* amount of overhead (but not too much as long as you
keep meaningful extend size). Autoextend also updates the file headers, and you
can run in to concurrency related to issues in the file header block if there
are many processes constantly trying to extend the files.
Wasn't this precisely what ASM was designed to avoid? As in: "you can add disk
anytime and it "rebalances" itself"? Looks like YAOF (Yet Another Oracle
Furphy)....
--
Cheers
Nuno Souto
in sunny Sydney, Australia
dbvision@xxxxxxxxxxxx
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