topic How to enable write cache on P600 SATA in ProLiant Servers (ML,DL,SL)

How to enable write cache on P600 SATA

Chi Wai Lee — Tue, 13 Jun 2006 04:50:07 GMT

I've got a P600 attached to 6 SATA drives.
The write performance on the array is mighty slow less than 5MB/s on a RAID6 config.

I'm fairly sure that this slowness is caused because the P600 has forced the drives to disable write caching. I've tried to enable the write cache thru device manager but the checkbox keeps reseting to disabled with an event log claiming that the driver doesn't support this feature.

Any ideas???

Using the same drives on the motherboard's SATA connectors give me speeds in excess of 100MB/s (striping obviously)

Re: How to enable write cache on P600 SATA

raadek — Tue, 13 Jun 2006 05:06:49 GMT

Hiya,

Have a look at this:
http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?lang=en&cc=us&taskId=110&prodSeriesId=466290&prodTypeId=329290&prodSeriesId=466290&objectID=PSD_EX050519_CW01

I know that you were looking for something more helpful, but at least it explains why the P600 behaves odd in your config.

Additionaly I would say - avoid RAID6, especially on SATA drives. It has DRAMATIC performance overhead, so rather choose RAID5 + hot-spare. Or, even better, RAID10 which would give you a decent performance with slightly less capacity.

Rgds.

Re: How to enable write cache on P600 SATA

Chi Wai Lee — Tue, 13 Jun 2006 05:29:58 GMT

RAID6 is now currently supported. I must point out that even with a 6 drive RAID0 config only achieves around 10MB/s write speeds. I've tried all RAID configs and different strip sizes. On a single drive RAID0(standalone) config, I can write at 4-5MB/s!!!!

I've tried difference OSes as well.

I know that RAID6 may is significantly slower than RAID5 and that it is also slower than RAID10. But until I sort out this terrible speeds, I'm not is a ready to set down in stone which RAID level.

I'm confident that the write cache is slowing things down. If I create a a software RAID0 with 2 drives on the motherboard SATA controller. I get excellent speeds. If I disable the write caches on these drives, the write speeds fall all the way to sub 10MB/s.

I've also had engineers round to replace EVERYTHING.

Re: How to enable write cache on P600 SATA

Michael Bunker — Fri, 20 Oct 2006 15:13:04 GMT

With RAID5 and RAID6, allow parity initialization to complete after the array is first created. Before parity init completes, the controller must perform slower regenerative writes instead of faster backed out writes to keep the disk parity data coherent.

The P600 does not allow enabling disk write caching do to the data lost possibility.

Re: How to enable write cache on P600 SATA

Michael Richter — Tue, 30 Jan 2007 10:01:14 GMT

At least use SAS instead of SATA Drives or use the 6-Port SATA Controller as a workaround/temp.

regards
mike