Improving hard disk performance on DL380

[Veedub]

Hi

I have a DL380 G3 with the following specs:

Dual 2.2Ghz Xeon
6GB RAM
Onboard 5i controller (no BBWC)
6 x 73GB 10K SCSI HDD in RAID 5

I am running VMWare ESX 3.5 on this server with 4 guest virtual machines. I find that hard disk performane is really quite slow. I want to try and improve the performance of the hard disks without spending too much money as the server will be upgraded in 6 months or so to a DL380 G5 or G6.

I was thinking that I would upgrade the RAID controller to a HP 6404/256MB with BBWC. I know this would improve performance, I presume mostly though because it will have 256MB of cache enabled with the BBWC. I was wondering though, would I get a significant performance boost by just adding a BBWC to the existing 5i controller? I can get a 6404 for quite cheap but am not sure how easy it will be to swap controllers while keeping the RAID array and all data intact so I need to consider this and the amount of time required to upgrade to the 6404.

Can anyone give me there thoughts on the best way to get as much HDD performance from this machine (without paying for new, faster disks that wont be able to be used in the new server). I am also playing with the thought if the RAID controller upgrade wont improve things enough of moving from RAID 5 to RAID 10. I should have enough disk space to be able to do this. Any thoughts on this option also?

Thanks
VD

[u84823]

Hi, there's really two issues here.

Firsly that you absolutely NEED the BBWC for ESX since it does NO write caching itself. Every sector write will involve five reads and two writes with a six disk volume. With the BBWC writes will be combined into complete stripes and physically committed when convenient.

Second a faster array controller will always be preferable. As it's ESX presumably you can copy the VMs elsewhere to start with, in case the upgrade is not smooth?

[Veedub]

Thanks for the input.

I do plan to add a BBWC but I suppose how I do that depends on two things. I either can add the BBWC to the onboard 5i or add a 6404 for 256MB of BBWC.

Can someone help with the following:

- What kind of performance difference can I expect by using a 6404/256MB as opposed to a 5i with BBWC. I should add that I don't have U320 drives, I have Ultra3 drives and don't intend on replacing these. Because of this, I suspect the only performance boosted will be achieve by having a 256MB cache vs a 64MB cache. Will this have a massive effect?

- Will I be able to swap the hard drives over to a 6404/256MB without breaking the RAID array and losing data (theoretically atleast) or will it require a rebuilding of the array and reinstall of ESX?

Thanks a lot.
VD

[Shayne Heidemann]

The array information is located on the hard drives and should move between the controllers with no action other than plugging them in.

That's the nice thing about Smart Array.

Always have a backup however, hardware can always fail.

The BBWC performance increase will depend on the application unfortunately.

Cheers
Shayne

[Pieter 't Hart]

look at this document to assist in your decision for an new controller.

http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?lang=en&cc=us&taskId=125&prodSeriesId=374803&prodTypeId=329290&objectID=c00180566

The 6404 comes at the end of the "high-end" list. but when not upgrading disks too the controller's cappacity is not challenged.

[SGeorge]

In VMWare pay attention also at the blocksize of the datastore (if you have local disks or iSCSI disks). Bigger blocksize will decrease the drive speed.