PP Size

[mrn]

Has anyone done any or seen any analysis on how the PP size of a disk affects I/O performance in general terms.

e.g.

PP Size
8mb - small files / large files read/write
16mb - small files / large files read / write
32mb - ...........

--
| Mike Nixon
| Unix Admin
|
----------------------------

 

[victorv]

hi,
I don't know relations between perf. and PP size:
usually the choice of PP size is forced by the disk size:

a VG has a maximum number of PP ( it's a AIX data ) ,
then if the disk is very large and you choose a little
PP size, you go over this limit, and AIX does not permit it.

The minimum size of a fs you can create is equal at PP size
(1 PP) : than if you choose PP size very large,
you have the problem that the minimum fs size you can create is (ie) 128 Mb, and this can waste your disk space.

bye

 

[ddlldd2000]

You can also use -t (mkvg or chvg) to change the limitation of 1016 pps/vg. But I really don't know the relationship between the perf and pp.

 

[azuret]

I dont think it should affect the performance of the system as the read/write are managed by inodes and fragmentation size. You may tune your VMM using vmtune command.
There's some helpful information in this redbook on system performance and tuning:

http://www.redbooks.ibm.com/redbooks/pdfs/sg246184.pdf

 

[mrn]

Thanks guys, but not realy what I'm after, I know about tuning but didn't want to re-invent the wheel. I'll do some testing myself.

--
| Mike Nixon
| Unix Admin
|
----------------------------