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P800 Raid 10 configurations and speed

Adam Gray
Occasional Visitor

P800 Raid 10 configurations and speed

I have just taken delivery of a DL380 with a P800 and an Storage Works 70 storage array. The server 2003 with SQL2005 designed to run two small disk intensive databases around 70GB each. So we asked for a array design splitting OS, Temp.db, Log files and Data onto separate arrays. Each database has its own log file array and data array. The design was based on Raid 1 for smaller arrays and Raid 10 for the larger arrays (4 and 6 drives).

The server turned up with Raid 5 for the larger arrays and when quizzing the engineer he said that the P800 when configured in a Raid 10 in fact does a Raid 5 with mirror. (Raid 5/1) . So there was little speed advantage and you were better off going for a larger Raid 5.

Is this actually the case. And if so what is the fastest way of configuring 4 and 6 drives on a P800 controller? Also does anyone know if 3 disk Raid 5 is faster than 2 disk Raid 1 on this controller?
2 REPLIES
Joshua Small_2
Valued Contributor

Re: P800 Raid 10 configurations and speed

I'll try not to get too contraversial in my answer here..

The whole thing you learn in SQL studies about "log files, temp files and data on different drives" really assumes you've three JBOD disks and then you gain the performance splitting up your load, because the three disks can be written to at once.

With modern RAID drives, any performance difference between one large RAID 1+0 drive containing everything, and several smaller logical RAID drives is debateable. The bandwidth limiter is generally the SCSI bus or fibre channel, which will be shared amongst all logical drives. You could even argue the single large drive option is better since you get to stripe ALL your data.

As to RAID1+0 vs RAID5, differences come down to whether you're doing more writing or more reading, but there definitely are differences. It's worth doing your research here and doing what you'd prefer, rather than blindly following an HP tech.


I'd also consider the following.. for 2x 70GB databases, you could have easily fit that much storage on a DL380 without the Storageworks investment. 5x 146GB drives in the onboard backplane should provide plenty of room to spare, and spare ports to grow in.
Adam Gray
Occasional Visitor

Re: P800 Raid 10 configurations and speed

Thanks Joshua,

In this scenario there will be substancial data written to the database and log files all the time. Around 10 (very small) transactions write per second. So splitting up the logs temp.db and data are definitely worth while. Those transactions will not require any reads.

The reads queries, will be around 50 per day. and will tend to be very large. So designing the storage was easy. many drives many arrays and don't up set the writes.

The main question was is what I was told correct. when configuring P800 to do a 1+0 it actually does a 5+1 instead. And if so I would be better off with a larger raid 5 for the data disk rather than configuring a 1+0 or 5+1. I don't require the extra level of redundancy I just require the speed.