Home > Workload Solutions > Oracle > Guides > Design Guide—Oracle RAC Database on PowerStore T Storage > Operating system devices and Oracle ASM disk group design
After the database volumes are presented to the database VMs as virtual disks, perform the following steps to prepare these virtual disks for Oracle ASM disk group creation:
KERNEL=="sd[a-z]*[1-9]", SUBSYSTEM=="block", PROGRAM=="/usr/lib/udev/scsi_id -g -u -d /dev/$parent", RESULT=="368ccf09800cd6a0eaf106e5a2155cf92", SYMLINK+="oracleasm/disks/ora-redo4", OWNER="grid", GROUP="asmadmin", MODE="0660"
The string “368ccf09800cd6a0eaf106e5a2155cf92” is the SCSI ID of the device.
# ls -l /dev/oracleasm/disks
lrwxrwxrwx 1 root root 10 Nov 9 10:21 ora-data1 -> ../../sdh1
lrwxrwxrwx 1 root root 10 Nov 9 10:21 ora-data2 -> ../../sdi1
lrwxrwxrwx 1 root root 10 Nov 9 10:21 ora-data3 -> ../../sdj1
lrwxrwxrwx 1 root root 10 Nov 9 10:21 ora-data4 -> ../../sdk1
lrwxrwxrwx 1 root root 10 Nov 9 10:21 ora-fra -> ../../sdf1
lrwxrwxrwx 1 root root 10 Nov 9 10:21 ora-ocr1 -> ../../sdc1
lrwxrwxrwx 1 root root 10 Nov 9 10:21 ora-ocr2 -> ../../sdd1
lrwxrwxrwx 1 root root 10 Nov 9 10:21 ora-ocr3 -> ../../sde1
lrwxrwxrwx 1 root root 10 Nov 9 10:21 ora-redo1 -> ../../sdl1
lrwxrwxrwx 1 root root 10 Nov 9 10:21 ora-redo2 -> ../../sdm1
lrwxrwxrwx 1 root root 10 Nov 9 10:21 ora-redo3 -> ../../sdn1
lrwxrwxrwx 1 root root 10 Nov 9 10:21 ora-redo4 -> ../../sdo1
lrwxrwxrwx 1 root root 10 Nov 9 10:21 ora-temp -> ../../sdg
The Oracle ASM disk groups are created based on these raw devices. To use the soft link alias for the devices, we set the DISK Discovery Path as /dev/oracleasm/disks/*, as shown in the following table. While the OCR disk group uses the normal redundancy setting (with triple mirroring), all other disk groups use the external redundancy setting. We used the coarse striping setting for the DATA, FRA, and OCR disk groups and the fine-grain striping setting for the REDO and TEMP disk groups.
ASM disk group |
Purpose |
ASM striping |
ASM disk group size (GB) |
Device alias in /dev/oracleasm/disks |
Virtual disk |
OCR |
OCR, voting disk, GIMR |
Coarse |
50 |
ora-ocr1, ora-ocr2, |
Hard Disk2-4 |
DATA |
Various database files |
Coarse |
2400 |
ora-data1, ora-data2, |
Hard Disk5-8 |
REDO |
Online Redo logs |
Fine-grain |
100 |
ora-redo1, ora-redo2, |
Hard Disk9-12 |
FRA |
Archive logs |
Coarse |
100 |
ora-fra |
Hard Disk13 |
TEMP |
Temp files |
Fine-grain |
500 |
ora-temp |
Hard Disk14 |
When ASM rebalances the disk group, a compacting phase at the end of the rebalance moves the data to the higher-performing tracks of the spinning disks. Because the PowerStore storage array uses all-flash devices, compacting the data might not provide any benefits. Effective from Oracle 12c, it is possible to disable compacting on individual ASM disk groups by setting the _rebalance_compact attribute to FALSE:
SQL > ALTER DISKGROUP DATA SET ATTRIBUTE '_rebalance_compact'='FALSE';