RAID 5 or 10 for 8 Disks?

[litkaj]

I'm going to be moving my forums to a new server and was planning on picking up one of the MONSTER boxes from The Planet.

The question floating around is whether I should go with RAID 5 or 10. My experience with RAID 5 and 10 performance is limited to arrays with 4 disks. I know that RAID 5 has a huge write penalty over RAID 10 when you look at a 3 drive RAID 5 array and a 4 disk RAID 10 array but how do they compare wit an 8 drive array? I would think that RAID 10 would actually suffer a read penalty over RAID 5 at that level because it's only striping over the 4 mirrors instead of over the 8 disks.

Any thoughts? Benchmarks?

[Dew]

Version 1.03 ------Sequential Output------ --Sequential Input- --Random-
-Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
Fedora5 10000M 37816 81 106135 50 35865 25 44662 89 180734 46 127.0 0
------Sequential Create------ --------Random Create--------
-Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP
16 2141 69 +++++ +++ 3760 71 2175 66 +++++ +++ 1378 52
Fedora5,10000M,37816,81,106135,50,35865,25,44662,89,180734,4 6,127.0,0,16,2141,69 ,+++++,+++,3760,71,2175,66,+++++,+++,1378,52

Here ya go
-100MB/sec sequential write, 35MB/sec random write.
-180MB/sec sequential read, 44MB/sec random read

This is RAID5 with 8 drives on a Highpoint RR2320.

[litkaj]

I don't suppose that you have similar numbers for RAID 10, do you? From what I've read over the past hour it looks like RAID 10 is going to be the way to go for a server heavy on MySQL usage.

[drizzt81]

if you are hosting a DB, RAID-10 has the advantage that each set of mirrors could -theoretically- work on a different pending request, improving the performance for lots of requests. Alternatively, if RAID-10 is implemented correctly, while one set of mirrors is reading LARGE_TABLE_A the second set could be reading LARGE_TABLE_B which you were going to join in memory.

I don't know what/ how it works in the real-world though.

[Volkum]

if you are hosting a DB, RAID-10 has the advantage that each set of mirrors could -theoretically- work on a different pending request, improving the performance for lots of requests. Alternatively, if RAID-10 is implemented correctly, while one set of mirrors is reading LARGE_TABLE_A the second set could be reading LARGE_TABLE_B which you were going to join in memory.

I don't know what/ how it works in the real-world though.

That's on a controller by controller basis. I've heard there are ones that will split read requests, but I haven't seen any evidence of any controller actually doing so. Maybe UM has some info on that ;)

[unhappy_mage]

I don't suppose that you have similar numbers for RAID 10, do you? From what I've read over the past hour it looks like RAID 10 is going to be the way to go for a server heavy on MySQL usage.
Stripe And Mirror Everything.

I'm running some tests on my machine with 4*15k 18gb disks in raid 0+1. It's on a fairly old controller, a Compaq array that uses the cciss driver, so I figure that if it does simultaneous reads, anything will ;) I just have to write the test first.... :-/

http://www.hardfolding.com/ftag1.php/mem/150072.png (http://www.hardfolding.com?go=38&tm=33&id=150072)http://www.hardfolding.com/utag1.php/mem/428/1.png (http://www.hardfolding.com?go=36&id=428&type=1)

[Rocco123]

Recently we moved 10 of our Lotus Notes servers from a 7 disk RAID 5 to a 14 disk RAID 10. We saw a huge performance increase after doing so. From past experience, we saw performance drops with using RAID 5 for any kind of DB stuff.

[eth00]

If you want max performance go with RAID10.

If you are not set on the datacenter of choice you may also want to checkout softlayer you can get a quad opteron with 16gb of ram for about the same cost, though not as much disk space for that case. They seem to have a pretty good network and reasonable support.

Personally I am a fan of ev1servers but they are pretty expensive on those higher end servers.

[litkaj]

Wel, I've already got a few boxes with The Planet so I'm going to stick with them. I've always been more than happy with their support and service. That's WAY more than I can say for EV1. I had a pair of servers with them a couple years ago and had nothing but problems. From support taking 24+ hours to return emails & phone calls, to making it difficult to cancel or add services, to their entire network going offline for an hour or two each month (and always right in the middle of the day). It made it very difficult to trust them with mission-critical services.

In any case, the server I'm replacing is Disk-I/O limited so I think this is the way to go. I've placed the order for RAID 10, thanks all.