Re: Performance with RAID5 / mirroring ?

On 29 Jan 2003 06:36:22 -0800, Mark.Powell_at_eds.com (Mark D Powell) wrote:

>LandRoverManREMOVETHIS_at_tiscalimail.nl (Hans van Dam) wrote in message news:<3e37be05.424238406_at_pollux.casema.net>...
>> On Wed, 29 Jan 2003 09:43:54 +0100, "RoBog" <robog_at_tin.it> wrote:
>>
>> >We have Oracle 8.17 (win NT) on 4 hd (data + index + redo + system)
>> >
>> >If we use RAID5 what's the impact on performance?
>> >
>> >If we use mirroring (4+4 hd) what's the impact on performance?
>>
>> RAID 0 = performance (striping)
>> RAID 1 = safety (mirrorring)
>> RAID 5 = compromise between performance and safety
>> RAID 0+1 = performance and safety without compromise
>>
>> Read all (?) about it at http://www.mylex.com/solutions/aboutrdr.html
>>
>> Groeten,
>>
>> Hans van Dam.
>
>Given a choice I would use OS level stripping with mirroring, but it
>data loss prevention is a very high priority I would not hesitate to
>mirror RAID-5. We run EMC and their version of RAID-5 is called
>RAID-S and we perform OS mirroring of the RAID-S disk system to a
>second RAID-S device. Performance is (amazingly) good.

That doesnt seem like a logical configuration to me. If you need mirroring and striping, the best choice is RAID 0+1 because a with mirrored RAID S you overdo things, because of the "redundant redundancy".

Furthermore OS mirroring is always slower and less reliable than hardware mirroring, even if you are satisfied it is not optimal and certainly not maximal.

So if you're happy with it, fine, but you can do better with less disks (= money).

Regards,

Hans van Dam. Received on Thu Jan 30 2003 - 06:45:00 CST