SD32k+xp12000 stripe size

[Steve Lewis]

Its finally arrived - my first Superdome. 32xPA8900 cores in 4 cells / 2 npars and a xp12000 with 6Tb and 20Gb cache. Its a DB and actuarial number cruncher. See attached photo.

200x16Gb OPENV (2+2) RAID 0/1 LUNs on the xp.
LVM + Online JFS, not vxvm.
HP put the LUNs in VGs (4Mb PE size and 38 LUNs per VG) for us.
HP-UX 11i v1.
No power path, just distributed the old fashioned way across all controllers.
100Gb filesystems and xTb of Informix DB in raw lvols.

4Mb extent-based stripe or use smaller LVM stripes?

I know that testing will decide above anything else, but I want a steer to get something up by Monday.

[Alan Meyer_4]

Such the proud papa, congratulations Steve ~warmsmile~

[TwoProc]

Nice box Steve, can we ALL come over and play on it too? :-)

4MB extent based stripes are great for us. If I remember correctly I wasn't able to use smaller ones b/c of a VG size limitation (max number of extents). In fact, in cases I've had to use larger.

I didn't know the 8900's were out - what speed are they?

[Steve Lewis]

Yes its my baby! [grins]

So I suppose a test plan is required

- different stripe widths and extent-based.
- different numbers of LUNs per stripe.
- then different DB page sizes.

[Alexandr Khristenko]

Ð hat use OnlineJFS with DB ----- the more decrease in speed

[Anthony Grouzdev]

Hi.

I think that the best performance configuration for OLTP system and this kind of hardware will be like this:


- create LVolumes with LVM-striping across all LUNs in VG, and round-robin shift of LUNs in striping for each LVolume(for additional balance the load);
- also optimize striping for all FC-paths;
- best stripe-size for random I/O is 64k.


LVM-striping is much better for performance than extend-base striping, because extend-base is not realy striping, it is extend-base destribution and performance depends on application very much in this case.

[Steve Lewis]

Thanks for your replies. We are currently doing some testing for different storage configurations - LVM stripes versus extent-based stripes.
We are currently only using about a quarter of an xp12000 with all 8 paths from the dome going to one ACP / 16 port adapter.
I read a post whch suggested striping across ACPs so another one of those may be an idea if we upgrade. Not sure about the likely percentage increase though.
The storage goes OK at the moment apart from simple Informix ontape backups where we appear to have hit an ancient bug to do with very old page timestamps. It crawls.

[TwoProc]

Steve, for performance reasons, you really should stripe across your ACP's. I don't think you're going to maximize the great hardware you've got without it. If you've not stood it up yet, it's not too late...