Oracle MVA

Tales from a Jack of all trades

Archive for the ‘VirtualBox’ Category

Shrinking thin provisioned ASM disks results in smaller diskgroup

with 5 comments

Just the other day I ran out of space on my laptop. That’s what you get with these “tiny” SSD’s nowadays. Anyway, when looking around where I had most data stored I found that an ASM disk in a VM was taking most of the space. This disk, as all my disks for VM’s, was thin provisioned. Usually I use some zero fill utillity overwrite the free space in a think provisioned disk so VirtualBox can shrink the disk. But this sounded risky to me for ASM, also those utilities need an ext filesystem.

Some googling learned me that I wasn’t the first one with this issue. Oracle actually supports a tool for this called ASRU: ASM Storage Reclamation Utility (ASMSRU must have been to long). So, easy comes easy does. Download the utility, fire it up ( ./ASRU -a sysasm DATA ) wait for some time and *presto* . 30 GB back of my 256 GB SSD. How cool is that!

Until about a week later I run into space issues in ASM in the VM I mentioned before. My ASM disk group was full. That sounded hilarious to me, since it was on a 40GB disk (checked it in VirtualBox and yes: still 40GB). Then I remembered ASRU.

Checking the v$asm_diskgroup showed something interesting:

SQL> SELECT name, total_mb, usable_file_mb FROM v$asm_diskgroup;

NAME       TOTAL_MB  USABLE_FILE_MB
--------- --------- ---------------
DATA          10090            1288

So, ASRU actually not only shrunk the disk, it also resided the disk group in ASM. Now how about that? I didn’t read any statement in the README file saying I had to resize my diskgroup after running ASRU….

SQL> ALTER DISKGROUP data RESIZE ALL;

Diskgroup altered.

SQL> SELECT name, total_mb, usable_file_mb FROM v$asm_diskgroup;

NAME       TOTAL_MB  USABLE_FILE_MB
--------- --------- ---------------
DATA          40954           32152

So, if you happen to use ASRU, don’t forget to resize your diskgroup or you will live in interesting times.

Hopes this helps.

Advertisements

Written by Jacco H. Landlust

January 13, 2013 at 3:16 pm

Posted in ASM, RDBMS, VirtualBox, VMWare