Re: H/W RAID 5 on slower disks versus no raid on faster

How are you going to make use of the three faster drives under 
postgresql?   Were you intending to put the WAL, system/swap, and the 
actual data files on separate drives/partitions?  Unless you do 
something like that (or s/w RAID to distribute the processing across the 
disks), you really have ONE SCSI 15K Ultra320 drive against 3 slower 
drives with the RAID overhead (and spreading of performance because of 
the multiple heads).

I don't have specifics here, but I'd expect that the RAID5 on slower 
drives would work better for apps with lots of selects or lots of 
concurrent users.  I suspect that the Ultra320 would be better for batch 
jobs and mostly transactions with less selects.

Charlie

Rajesh Kumar Mallah. wrote:

>Hi folks,
>
>I have two options:
>3*18 GB 10,000 RPM Ultra160 Dual Channel SCSI  controller + H/W Raid 5
>and 
>2*36 GB 15,000 RPM Ultra320 Dual Channel SCSI and no RAID
>
>Does anyone opinions *performance wise*  the pros and cons of above 
>two options.
>
>please take in consideration in latter case its higher RPM and better
>SCSI interface. 
>
>
>
>Regds
>Mallah.
>
>
>
>
>  
>

-- 


Charles H. Woloszynski

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