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Yeah, i would agree with Morgan that RAID 5 is not the demon it is made
out to be.
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.
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.
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.
cheers
anand
Received on Mon Dec 05 2005 - 05:53:31 CST