How do you RAID yours?

[SM_3]

How do you decide what RAID level to use?

RAID5?

RAID1+0?

I'm sure there are lots of different factors involved!


Thanks

[Pete Randall]

My preference is always RAID 0/1. If I'm tight on disk space I'll consider RAID 5 for a non-critical application. If the app is critical I'll try my darndest to get enough disk space to go with RAID 0/1.


Pete

[SM_3]

Pete

What about 1+0?

[Patrick Wallek]

I agree with Pete. If you have the money for the disk space, the RAID 1+0 is the way to go. You will definitely see much better performance with it.

With RAID 5 you have the overhead of the parity calculation for every write to disk and that takes time and resources .

The question is always cost though. With RAID 1+0 you need *double* the amount of disk space since you basically have 2 copies of the data. RAID 5 doesn't have quite that space overhead but you will still not get the full capacity of your array.

[A. Clay Stephenson]

In general (although it can be somewhat mollified by an array with lots of cache), RAID5 typically imposes a 5-7x performance hit over RAID 1/0. You have to decide which is the more important: speed or disk utilization. In almost all cases these days, speed wins.

[Pete Randall]

SM,

What you refer to as RAID 1+0 is what I was calling RAID 0/1 - it's the same thing.


Pete

[Jeff Schussele]

And I call it RAID 10

But as mentioned the RAID type is almost always determined here by the ultimate goal:

SPEED = RAID 10

Economy AND Size = RAID 5

And Clay is correct i.e. a lot of the performance hit from RAID 5 can be mitigated by HW caches of a healthy size on the arrays.

My 2 cents,
Jeff

[Leif Halvarsson_2]

Hi,

We are going to do a storage consolidation and replare several older systems with one large (perhaps an EVA 5000).
For filesystem (file servers) we are planning to use RAID 5 and for databases (Oracle) RAID 10.

[Joshua Scott]

Cost is a major factor. consider this (using a VA7410 with 36GB drives as an example:

15 drives:
RAID5DP: $225.78/GB
RAID1+0: $361.24/GB

30 drives:
RAID5DP: $127.62/GB
RAID1+0: $229.71/GB

45 drives:
RAID5DP: $99.57/GB
RAID1+0: $185.87/GB

60 drives:
RAID5DP: $86.29/GB
RAID1+0: $163.95/GB

HTH!
-Josh

[SM_3]

I was under the impression that Raid 0+1 and 1+0 were different (I saw this...)

http://www.ofb.net/~jheiss/raid10/

[Patrick Wallek]

Yes, 0+1 and 1+0 are somewhat different, as pointed out by the web site you reference. Trying to figure out the difference always makes my head hurt! ;)

Either way you go you will usually get better performance with 1+0/0+1 than with Raid 5.

[Pete Randall]

The HP units I'm familiar with (AutoRAID, FC60) offer RAID 0/1: that is exactly the way it's described in the manuals for both. The VA7410 uses RAID 0+1 (see http://h18006.www1.hp.com/products/quickspecs/11558_div/11558_div.html ). The subleties of what may be meant by RAID 0/1, RAID 0+1, and RAID 1+0 elude me, but I think it's safe to say that any of the above offer full mirroring with some form of striping. So, in the context of your original question, I would always choose a stiped, fully mirrored configuration, whether it is described as 0/1, 0+1, or 1+0 (or even Jeff's "10").


Pete

[SM_3]

Thanks guys.




Can't seem to assign any points!

[Alzhy]

If your're using Cache-Centric Arrays (ie. Hitachi line -- HDS 9960, 8880; HP XP256,512,1024;Sun Storedge 99xx), I would have RAID5 LUNs presented to servers and observe "strict" volume (of LVOL) building/asembly procedures. Ours is to further do RAID0 (striping) of these already "RAIDed5" LUNs as long as we are sure that these LUNs belong to different Array-Controller pairs (or ACP's). Still on other really highly available configurations where speed is really not a factor -- we RAID5 these already "RAIDed5" Luns accross FC connections if we are not using DMP mode on the ports -- for path protection.
.
For Controller Centric Arrays (such as the EVA), one can do benchmarks between RAID0+1 and RAID5 LUN configurations to determine which would meet application requirements. For mostly OLTP (50r-50w) transactions -- my experience has so far shown that RAID5 luns are sufficient BUT in RDBMS configurations -- at least a dikgroup of RAID0+1 LUNS be set aside for redo logs... for mostly DSS/Datawarehouse apps -- it would be RAID0+1.
..
All other requirements ie. Fileserver filesystems -- RAID5 would do...

[Steven E. Protter]

Answer: All of the above.

Explanation:

OS is on two local disks. Exact Raid 1 mirror copy using mirror/ux

Oracle data is on a Xiotech Magnitude Disk array. RAID 10.

Binaries and executables that aren't part of the OS are on that same disk array, Raid 5 nine bit parity.

I can't say I'm happy about it, but the situation seems pretty reliable.

SEP