performance issue with vg

[Kgreen]

Hi,

If i have "PE Size (Mbytes) 4" instead of 16 , will I have performance issues with applications and databases such as oracle. If I would what and how can they be ?

[Pete Randall]

PE size, combined with MAXPE per volume, limits the size disk you can use within your VG. If specified too small, later attempts to introduce larger size disks will require that the VG be re-created from scratch, since the only time either of these can be specified is at vgcreate. The performance implications are minimal if any.


Pete

[Kgreen]

Thanks , I wont be going for larger disk anyway. I was more interested in knowing issues with performance if there could be any

[Hein van den Heuvel · Accepted solution]

Smaller PEs require more adminstrative overhead for the same memory, but I soudl think that is neglectable.

Smaller PEs do not permit large volumes, but you state that is no issue and it certainly has no performance impact.

A 4MB PE still holds 512 average sized (8KB) db pages, so there is little risk of excessive 'split IOs' accross extents.

Small PE will increase the chances that data is spread over mutliple spindles which has the potential to increase throughput on busy systems, balancing IO better.

So on the whole I expect better performance from smaller PE's.

fwiw,
Hein van den Heuvel
HvdH Performance Consulting.