Hi Finn/Greg I am still confused (although i do agree with ideas of Greg) Is there a paper which describes whats the ideal combination of disks and sik sizes for ASM. I am using external redundancy should i still be worried about having only 2 disks ? I am planning to add 2 2000Gb disks and then simulatenously drop the 6 50Gb disks so rebalance is a single operation regards Hrishy --- On Sat, 8/11/08, Greg Rahn <greg@xxxxxxxxxxxxxxxxxx> wrote: > From: Greg Rahn <greg@xxxxxxxxxxxxxxxxxx> > Subject: Re: ASM LUN sizes and number of disks > To: finn.oracledba@xxxxxxxxx > Cc: hrishys@xxxxxxxxxxx, oracle-l@xxxxxxxxxxxxx > Date: Saturday, 8 November, 2008, 4:36 AM > On Fri, Nov 7, 2008 at 6:55 PM, Finn Jorgensen > <finn.oracledba@xxxxxxxxx> wrote: > > 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 agree with this... > > > You will have to add those disks to a separate > diskgroup and then start > > moving data over, which means downtime. > > but could you not add(2x200)/rebalance, > drop(6x50GB)/rebalance to get > all the data onto the 2x200GB? > this would alleviate downtime but... > > I would never put my whole database only on 2 spindles > anyway. If I > recall correctly, if there is not room to mirror ASM > extents from the > failed drive, the diskgroup will dismount to protect from > catastrophic > failure. This means in a two disk ASM group, losing one > disk will > result in a down database. There there is also a special > case with 3 > disks, as each is in their own failgroup and I believe the > usable > space (for files) for 3 disks is the same as 2 disks (or > something > similar). So basically the minimum recommended disks is > four. It > comes back to disk space is cheap... > > > -- > Regards, > Greg Rahn > http://structureddata.org -- //www.freelists.org/webpage/oracle-l