lvm

[Indrajit Bhagat]

what do you mean by strict alocation .

[James R. Ferguson]

Hi:

"Strict allocation" simply means that the mirrored extents of a logical volume must reside on different physical disks or physical volume groups.

Mirroring is a high-availablity technique. If you allowed mirrored extents to reside on the same physical disk, failure of that disk would render ALL of the data unavailable. That's not "high availability".

Regards!

...JRF...

[Fabian Briseño]

hello. Indrajit.

Check this link out.

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=1118436

[Patrick Wallek]

Have a look at the 'lvcreate' man page, specifically the section regarding the '-s' option to lvcreate.

That should explain it fully.

[whiteknight]

Strict Allocation
=================
The purpose of disk mirroring is to have the data stored on more than one disk
in case of a disk failure. The lvcreate command sets the "strict" allocation
policy by default. This means that mirrors of a logical extent cannot share
the same physical volume.

The default value can be overidden by using the "-s" option with the lvcreate
(1M) or lvchange(1M) commands. The possible values for the "-s" option are:

1)y Set a strict allocation policy. Mirrors of a logical extent cannot share the same physical volume. This is the default policy.

2)g Set a PVG-strict allocation policy. Mirrors of a logical extent cannot share the same physical volume group. To learn more about physical volume groups see the vgcreate(1M) man page.

3)n Do not set a strict or a PVG-strict allocation policy. Mirrors of a logical extent can share the same physical volume group.


WK