Re: ASM LUN sizes and number of disks

  • From: "jason arneil" <jason.arneil@xxxxxxxxx>
  • To: finn.oracledba@xxxxxxxxx
  • Date: Mon, 10 Nov 2008 09:14:43 +0000


2008/11/8 Finn Jorgensen <finn.oracledba@xxxxxxxxx>

> Because of the way ASM distributes data evenly across all disks in a
> diskgroup, adding 200GB disks to an existing diskgroup comprising of 50GB
> disks means you will never be able to use more than 50GB of those 200GB
> disks.

I think it's worth emphasising that ASM attempts to fill each device in a
diskgroup up to the same CAPACITY.  So a device that is x 4 the size of
another device within the same diskgroup should in theory receive 4 times
the number of extents meaning it would be able to be filled beyond the 50GB.

As long as you rebalance when adding the device so that the 50GB are not
full already!

> You will have to add those disks to a separate diskgroup and then start
> moving data over, which means downtime.
> Finn


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