topic Re: PE size in Operating System - Linux

PE size

unre4l — Tue, 19 Jun 2007 16:23:09 GMT

When creating LVMs in the GUI setup for redhat the default PE size is 32 mbs for LVM. I know that a lot of it might be application related but say for an oracle database is there any recommended size for PE's when creating LVM's. Is 32 mb the default good or does a 4mb PE work better?
Thanks.

Re: PE size

Stuart Browne — Tue, 19 Jun 2007 16:59:38 GMT

The extent sizes for LVM PE's really depends on how large you want to size the PE up to.

Under LVM1, you were limited ot 65536 extents per PE, thus if you used 4mb extents, you're limited to a 256GB filesystem. This is what you'd be using under RHEL3 or a 2.4 series kernel. Scaling up the extent size allows you access to a larger resultant filesyste (up to 1TB due to a signed integer being used).

Under LVM2 on a 2.6 series kernel (RHEl4+), this limit has been fixed, so you can use any extent size you want, and create a filesystem up to 16TB on x86 and 8EB on a 64bit kernel.

If you're dealing with large amounts of data, it's highly suggested you go for a larger extent size for performance reasons. RH uses the default of 32MB for a reason.. ;)

As you intend to use Oracle, you're talking large-chunks of data, so the larger extent size would suit you better in my opinion.

Re: PE size

Ivan Ferreira — Tue, 19 Jun 2007 19:18:02 GMT

You should be concerned more in the file system block size. As described above, the PE size limits the size of the LV.

Re: PE size

skt_skt — Tue, 19 Jun 2007 20:19:50 GMT

We have around 100 linux servers and we use the default size 32MB.We dont use any LUN more than 100GB.