topic Optimum disk layout in Operating System - HP-UX

Optimum disk layout

David J Ryan — Thu, 11 Oct 2007 03:24:37 GMT

Hi,
I have an rp4440 with a MSA30. We have had disk throughput issues and I am reviewing the disk layout. We have 1 LV with two mirror copies. The LV is lvsplit overnight to allow offline backup and lvemerged at the end. Currently it is contained on three PVG's with 6*73gb disks in the vg. The app causes v.high logical reads and I am trying to decide the best layout (striped, mirrored, both?) Any advice would be appreciated. OS is HP.UX 11.11. We have Mirror-UX.

Re: Optimum disk layout

Aneesh Mohan — Thu, 11 Oct 2007 03:42:04 GMT

Hi David,

I feel better to create a lun ,RAID 1+0 in MSA and have one mirror copy in OS .

Thanks,
Aneesh

Re: Optimum disk layout

Steven E. Protter — Thu, 11 Oct 2007 03:46:43 GMT

Shalom,

Heavy read applications generally perform best in a RAID 5 environment.

If there is heavy write activity, these logical volumes will perform better raid 1 or raid 1+0.

Since you have only and MSA-030, you can't do RAID on the hardware. If you had an MSA-1000/1500 fiber channel switch, you could handle raid on the hardware.

In general, its best to handle RAID on the hardware, not with OS software. Mirror/UX in this case should be used if you want to implement RAID 1. Striped can be done with LVM.

SEP

Re: Optimum disk layout

Torsten. — Thu, 11 Oct 2007 05:06:10 GMT

Is your MSA30 connected to "simple" SCSI controllers or a smart array? Does it have SB, DB or MI modules?

With your OS version, you cannot have striped mirrors, only extend based. But even this could help you.

Re: Optimum disk layout

David J Ryan — Thu, 11 Oct 2007 05:45:58 GMT

Hi Torsten,
It is SCSI 4 channel path no smart array

Re: Optimum disk layout

Hein van den Heuvel — Thu, 11 Oct 2007 06:59:38 GMT

David,

Welcome to the HP HPUX ITRC Forums.

Unfortunately I can not see your attachments from the thin client I am currenty on which does not support .doc files. Use .txt next time?

3 disks is an 'odd' number, as well as a small number!
Is it just those 3 containing main and mirrors or an other 3 for mirrors?
Did you manage to define the mirrored lv's such that they do not reside on the same physical spindle or just let the blocks drops wherever?
The cheapest way to fix this may well be to just add more drives, as long as you have slots available.

With so few spindles, placement withing the spindles may become critical. For example, you may want the critical, high IO rate, data on the outside (lower blocks) of the disk and low used zones (swap) explicitly on the inside. That may give lower seek average distances, and faster transfer rates.

Still, any ond all of this tuning will likely result in less than 20% differences. To make a real impact, look back at the application (undisclosed?!) and see if it can be aranged more smartly, given more (cache) memory to play with and such. That often easily gives 2x or 10x reduction in io rates.

Your mileage will vary!....

Hope this helps some,
Hein van den Heuvel
HvdH Performance Consulting.

Re: Optimum disk layout

David J Ryan — Thu, 11 Oct 2007 07:15:28 GMT

The disk layout is 6 disks, with strict mirror policy. 2 + 2 + 2. The third copy is used for the lvsplit offline backup, the other four maintain mirrored pair for the live service during the backup. The app is propriety software (no recognised db solution like ORACLE). It uses OS buffer cache.

Re: Optimum disk layout

Torsten. — Thu, 11 Oct 2007 07:28:24 GMT

Could you post

ioscan -fn
vgdisplay -v
strings /etc/lvmtab

the config is still not clear to me.