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Re: Raid definitions

Stephen Carville wrote:
Lord of Gore wrote:
McDougall, Marshall (FSH) wrote:
I am in the process of allocating drive space in several new servers.
Each of these servers are to house DB's of some sort.  Each has 6 X 146
gig drives and each will run RHES4.  I was thinking of 2 arrays:

1 - mirrored pair of 146's for OS
1 - Raid 5 array with 4 x 146 for db's.  That would give me a disk of
about 440 GB.

Currently, the biggest DB is about 30 GB.   I figure there are just too
many ways that I can slice and dice it.  Any advice appreciated.

Regards, Marshall
I'd go with level 5 for the extra space. Fault tolerance is the same: just 1 broken disk per "session" :) .

A four disk RAID 10 set can lose up to two drives without failing as long as both are not in the same mirror set.
Seems to me that I have to copy paste definitions from e-books. Of course in RAID 10 bla bla bla and the guy seems to know a little about these things, there's no need to clog this thread with useless info. I said I'd go for lvl 5 for the space. Anyway I think that bottlenecks are more likely to occur at hdd space level instead of hdd access time. But these are questions that should be answered by mr. McDougal. So, mr McDougal what kind of work will do these db's of yours? Give us a little more infos on the subject. We've got ourselves a very meticulous reader. While at it see how much it would cost to expand the array. It's a meticulous question.
RAID 10 has much better read and write performance than RAID 5. Should a drive fail, rebuilds to the replacement drive are faster making the window for a catastrophic failure less.

Well indeed it seems that although unnecessary we should dig a lot more and give mr Marshall a headache and suggest him that he should use drives from different manufacturers to lower the possibility to have 2 drives fail in the same time. But I have a strong feeling that he has all the disks from the same manufacturer. So given the fact that they are manufactured in approximately the same time they are subjected to the same stress and therefore fail in approximately the same time. In this case he should forget about servers and in fact about the whole IT thing and go to a monastery. Or he should try enterprise solutions like RAID 6 or even better 0+1+5 or 0+1+6 if hardware permits it and hope that the giggly girl from PR that he likes so much (no offense mr Marshall I'm just using her to make a point :) ) and pays him every once in a while a visit while bringing him a cup o coffee doesn't spill it on the servers. Or, and I think this is the best solution and the *complete* answer, we could let Marshall know what *we* as singular individuals would opt for and let him choose and forget about posing in the "know it all" Batman arret.


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