[SunHELP] RAID 3 No. of disks

[Rob Fielding]

Ketan Vora wrote:
> My requirement is a small no. of large file transactions and RAID 3 stripes
> data across multiple drives to achieve high performance throught parallel
> disk I/Os. Hence I'm looking at RAID 3 only.

RAID 5 and just pure striping all use parallel disk I/Os. RAID 5 brings the parity into the volume, therefore having total redundancy, however you're 
reading/writing more. Since everything is in parallel the penalty isn't as bad as having the parity disk fall over, IMO

> Now I want to know if more disks will give better performance?

More controllers would give more performance. But then you've got issues on bus speed of the machine etc (ie you don't want to saturate that ;)

There's no simple answer. You have to benchmark your application cross different RAID configurations to best determin things like the effective stripe 
size, controller limits and disk numbers. Extended analysis might show the array isn't the bottleneck.

Details you need to include into a posting to sunhelp should probably include more info. Do you want reliability, performance, disk space?  All ? You 
sound like you want lots of performance - therefore do you need realiability. Straight striped array would give best performance with zero redundancy. 
A combination of mirrored disks and stripes them might give better performance with redundancy but an inefficient use of disk space. RAID 5 returns a 
more effecient use of storage, with more performance trade offs.

Are you using RAID controller cards, or is this a software RAID setup ?


> 
> Any ideas?
> 
> Rgds,
> Ketan
> ----- Original Message -----
> From: "Rob Fielding" <rob at dsvr.net>
> To: "Ketan Vora" <kvora at locuz.com>
> Sent: Thursday, April 24, 2003 5:52 PM
> Subject: Re: [SunHELP] RAID 3 No. of disks
> 
> 
> 
>>Ketan Vora wrote:
>>
>>>Hi,
>>>
>>>I want to implement RAID 3 on the new SE3510 (2 RAID controllers with 12
> 
> * 36
> 
>>>GB 15K rpm HDDs) in 8+1+1 config (8 disks, 1 parity disk and 1 Global
> 
> hot
> 
>>>spare). If I make this 10+1+1, will there be an increase in performance?
>>>
>>>Will more disks result in a better performance?
>>
>>I didn't think anyone would use RAID 3 or 4 anymore. 1 dedicated parity
> 
> disk just sounds like a noose around your neck to begin with.
> 
>>Why not raid 5 the lot, to two stiped raid 5 arrays ?
>>
>>Cheers,
>>
>>Rob
>>
>>
>>
> 
> 
> 


-- 

Rob Fielding
Development 	Designer Servers Ltd 	www.dsvr.co.uk