How we can reduce the time for mirroring a root disk.

[Silver_1]

Gurus,

Is anyway can we make the root mirroring, lvextend -m 1 command to do its job faster ?

As i know we can increase the buffers in Netware to do the mirroring faster..

Tx,
Nair

[RAC_1]

The time taken will depend upon size of the lvol, pvs involved in it.

You can not do much except that you can increase the priority of the process of lvextend.

[Sivakumar TS]

Dear Nair,

there is no concurrent remirror requests and remirror block size in HPUX as in Netware, alternatively you can try this.

Mirror the disks before you install the OS / restore the data, ie..

first create the LV ,
extend it... ( -m 1 )
then restore the data...

in this case, without the data, the mirroring would be faster.

With Regards,

Siva.

[Geoff Wild]

Best way - use faster disks - like 15,000 RPM ones...

Rgds...Geoff

[Victor Fridyev]

Nair,

As it was mentioned, you can do almost nothing in order to reduce time of mirroring, but, IMHO, it's not a critical thing. First of all, you can run mirroring in parallel with a normal jobs, it does not decrease performance significantly.
For new machines the process does not take more than 1 hour, even for 72 GB disks. Look at the attached script, it builds mirroring for system disks.
HTH

[Sanjay_6]

Hi,

You do not have control over the time it takes to do the mirroring. The only thing you can do is use faster disks.

Hope this helps.

Regds

[Luk Vandenbussche]

If you mirror a volume when you create it then it is done immediatly

lvcreate -m 1 ..

[Bill Hassell]

The only way to get instant morroring is to create the lvol (as mentioned) with the -m 1 option (hundreds of GB can be created and mirrored in just a second or two). But when you extend the lvol, some very detailed code will lock a block from being written, copy the block, verify that the block was copied correctly, then marks the copy as synced and unlocks the block. This is why you can run the system at the same time as syncing the disks. It is also why it takes a long time. You don't want to skip any of these low level steps or you'll have a mess.

[Zubek, Mathias]

Hi Nair,

creating mirror before extending it as suggested by admins before is OK, but not helpful for you in case of mirroring the root. Try enabling the writecache temporarly on the disks. This sometimes boosts the measured IO- rate in iostat up to 50..100% ! It depends on your environment (disk, controller, machine..).

scsictl -a -ir=1 -a /dev/rdsk/cxtydz

Regards

Mathias

[Lolupee]

do the mirroring when nothing is happening to the disks or on single user mode. but I bet the gain would not be significant.

[Silver_1]

Thanks