Turning off Strict Allocation

[WSS]

Can someone please tell me the consequences of turning off Strict Allocation on a logical volume so I can extend the logical volume?

There is enough space to extend it to what I want, but won't allow me cause of Strict Allocation is true, and would like to know why.

Thanks in advance.
Trev

[James R. Ferguson · Accepted solution]

Hi Trev:

Strict allocation (when true) prevents mirrored extents of a logical volume from being allocated on the same physical volume.

To allow mirrored extents to occupy the same physical volume (if strict allocation is OFF) defeats the whole value of mirroring! A failure in a physical volume then means a loss of the logical volume at large.

Strict allocation, is analogous to a red traffic light. Obeying it keeps you from hurting yourself.

Regards!

...JRF...

[Patrick Wallek]

Is this LV mirrored? If so, the strict allocation prevents you from having both the original and mirror copies of extents on the same volume. Yes, it is possible.

To turn strict allocation off you would use lvchange.

# lvchange -s n /dev/vg??/lvol?

[Geoff Wild]

As James says - don't turn it off.

More info on mirrors here:

http://docs.hp.com/en/B2355-90672/ch07s03.html

Rgds...Geoff

[WSS]

Thanks for your input everyone...

So reading some more doco, it looks as though you can change a Strict Alloction policy to n lvchange -s n, but once you've done that you can't change it back to Strict? Is this correct?

Trev

[Geoff Wild]

Well - once you've removed the strict, and used extents on the same disk - then you can't go back - only way would be to delete the lvol and recreate it and restore your data.

Rgds...Geoff

[WSS]

Thanks for your comments guys.... Much appreciated.
Points awarded :-)
Trev

[Patrick Wallek]

>>Points awarded :-)

Really? Not that I can see.

[WSS]

>>Really? Not that I can see.

Happy?
Not sure why it didn't allocate first time around!