Re: A DBA philosopical question

ORA600 wrote:
> Yeah, i would agree with Morgan that RAID 5 is not the demon it is made
> out to be.
>

Think you got it wrong... Daniel does not sound like a RAID-5 supporter (unless it's Apples RAID - with new, all improved, DUAL XOR machines!)

> i mean, consider the fact that these days you have ridiculously high
> capacity disks like 146GB, 300 GB for SAN boxes. You can potentially
> have a Terabyte of storage with just 4-5 disks for RAID 5 and 8 odd
> disks for RAID 0+1.

Still a SCSI believer, eh? 500GB SATA: 4 disks for 1TB RAID 01!
>
> Well, for an IO intensive application that is bad news...because you
> only have a few disks but many Gigs of data to read and write...
>
> The key thing is IOPs and the thoroughput. and how much does your
> application need? what can the SAN do...? how many controllers do you
> have?
>
> With RAID 0+1 or 1+0, you just halve the no.of spindles and that is a
> problem. If you want to add capacity, you can add a Terabyte worth of
> storage with just 4 disks but for RAID 0+1, you only get 2 disks added
> to the Array Group for your application!!
>
> that doesn't add much to total thoroughput, if you have a large
> enterprise application or an application that is IO intensive.
>
> RAID 5 can help and by using SAME, you can use all the disks though
> with a potentially slow write speed. But, that can be offset due to the
> no.of arms present and you can get some very good write thoroughput.
> The SAN cache is another thing that can help write speeds.
>

RAID 5 (and RAID-2 for that matter) will always be slower than a similar hardware RAID10, as there's the penalty of checksum calculation.
SAME would be RAID10 (Stripe And Mirror Everything, so I fail to see you point, as in the paragraph above you see to find RAID10 counter-productive?

> Its a lot more complicated to design, implement the correct SAN
> solution and extract the best throrougput for your application and like
> always, testing is vital.
>
> RAID 5 can help if you design and implement it properly for your Oracle
> database.
>

So can a lead pipe (if designed and implemented properly).

-- 
Regards,
Frank van Bortel

Top-posting is one way to shut me up...