Using files on a shared drive as disks for ASM (on RedHat Linux)

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Firstly, you need to create files padded to the required disk size. So if you want 4 1Gb files you could execute the below commands on shared storage:

dd if=/dev/zero of=/SHAREDDISK/asmDisk1-1 bs=1024k count=1000

dd if=/dev/zero of=/SHAREDDISK/asmDisk1-2 bs=1024k count=1000

dd if=/dev/zero of=/SHAREDDISK/asmDisk1-3 bs=1024k count=1000

dd if=/dev/zero of=/SHAREDDISK/asmDisk1-4 bs=1024k count=1000

dd creates your file, ‘if’=/dev/zero gets null characters to populate the file with. ‘of=’ is the name of the file to create.

‘bs=1024k count=1000’ specifies the file size. This is 1000 times a 1024k byte size.

 

Next, you need your nodes to recognize your new files as a disk or device and you do this by attaching a loopback adapter:

On BOTH nodes

create a loopback to represent a disk

/sbin/losetup /dev/loop1 /SHAREDDISK/asmDisk1-1

/sbin/losetup /dev/loop2 /SHAREDDISK/asmDisk1-2

/sbin/losetup /dev/loop3 /SHAREDDISK/asmDisk1-3

/sbin/losetup /dev/loop4 /SHAREDDISK/asmDisk1-4

If you get a device busy message

ioctl: LOOP_SET_FD: Device or resource busy

delete the current device with:

/sbin/losetup -d /dev/loop1

And try again.

 

The next step is to create the actual ASM disks. This assumes that you have already installed the appropriate oracle ASM packages and kernel module.

On one node

Create your ASM disks:

 oracleasm createdisk DISK1 /dev/loop1

oracleasm createdisk DISK2 /dev/loop2

oracleasm createdisk DISK3 /dev/loop3

oracleasm createdisk DISK4 /dev/loop4

On both nodes:

oracleasm scandisks

oracleasm listdisks

 

Lastly, put the following lines into /etc/rc.local on both nodes so that the disks come back after a reboot.

/sbin/losetup /dev/loop1 /SHAREDDISK/asmDisk1-1

/sbin/losetup /dev/loop2 /SHAREDDISK/asmDisk1-2

/sbin/losetup /dev/loop3 /SHAREDDISK/asmDisk1-3

/sbin/losetup /dev/loop4 /SHAREDDISK/asmDisk1-4

oracleasm createdisk DISK1 /dev/loop1

oracleasm createdisk DISK2 /dev/loop2

oracleasm createdisk DISK3 /dev/loop3

oracleasm createdisk DISK4 /dev/loop4

/usr/sbin/oracleasm scandisks

 

This is because, at the point when scandisks is ran normally, your new disks will not be mounted so you need to force it to be done later.

Your new ASM disks should now be visible on all of your nodes.

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