Originally posted by: PontiacGeronimo

hello,

what are the rules for DISK BLOCK SIZE which we see on lsvg VG output?

sometimes this block size is seen set to 512 and sometimes 4096, what it depends of?

I don't see it is customizable in mkvg/chvg commands.

How does mkvg decides what block size disk has / will have?

What influence DISK BLOCK SIZE eg. 4096 has on jfs2 block size (agblksize)?

kind regards,

Originally posted by: DukePrg

It's the physical sector of physical  volume (PV) and most PVs are divided to 512 bytes.

Originally posted by: PontiacGeronimo

I am wondering where 4096 DISK Block SIZE in my VG comes from on my system, how system decided to create 4096 instead of 512.

the VG is built of 1 huge SAN disk

Originally posted by: AncientAIXer

man of crfs:

-a agblksize={ 512 | 1024 | 2048 | 4096 }
    Specifies the JFS2 block size in bytes. A file system block is the smallest unit of disk storage that can be allocated to a file. The default block size is 4096 bytes.

It defaults to largest, change if desired.

Originally posted by: wloszczowa

I guess this is not exactly agblksize - please note he mentioned parameter in VG, chfs has nothing to do with VG settings, it is rather for filesystems