Minimum size requirement for a lock disk in an MC/SG cluster

[Juan Gonzalez_2]

Is there a minimum size requirement for a lock disk in an MC/SG environment? I have not found any information on how what is the maximum size and what is the minimum size for a lock disk. Does any one out there know what gets written to this disk if any thing at all?

[Michael Steele_2]

It just needs to fit within the LVM header which is the size of one PE. The default PE size is 4 mb while 1 mb is the minimum.

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0xedf85dc05a7ad711abdc0090277a778c,00.html

[Sunil Sharma_1]

Hi,
There is no size spec for lock disk it can be as small as 4 MB. It doesn't write anything on disk except LVM normal LVM info.
MC/SG doesn't write anything extra on this disk.

Sunil

[melvyn burnard · Accepted solution]

There is no specified limit for a cluster lock disc.
As you can use it as a norml shared data disc, the maximum would be more a functionality of LVM than SG.
As for a minimum, we have had it running fine on a 2Mb LUN on an EMC array, and in fact have tested it to work even less htan that.
The only thing SG does wiht the disc is to write the cluster id in hte LVM headers, and to use the Bad Block Relocation area to mark it as the cluster lock disc.

[V. V. Ravi Kumar_1]

Hi,
MC/SG has no limitations on size of Cluster lock VG. MCSG doesn't write any thing on the VG, it's only LVM that controls the VG. It is only to specify which VG should be locked when the cluster is made up, since it is a shared VG.

Regards

[Juan Gonzalez_2]

Thank you all for the information specially Melvyn gave more import imformation.