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Raid 5 vs. Raid 10

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Raid 5 vs. Raid 10 - 9.Aug.2011 1:58:01 PM   
sabel9579

 

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Hi all,

Its been awhile since I have been on this forum. I would like to get a consenus on whether it is better to use a Raid 5 vs Raid10 for the Exchange Databases in 2010. I will be using an HP MSA 70 with 25 300GB SAS drives. I figured chopping them up into 5 separate luns for the databases. With the amount of space I am fortunate enough to have (only supporting 1500 users) I think I could do 5 Raid 10's at 600GB each (with a hot spare) and that would be more than sufficient.

Thoughts?
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RE: Raid 5 vs. Raid 10 - 9.Aug.2011 2:16:47 PM   
mark@mvps.org

 

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RAID 5 performance on those very low-spec systems is diabolical so for that reason alone I would advise you to steer clear of the number 5 at all costs.
You need to balance the IO that you can get out of the ox with both RAID types versus the capacity you need. If your IO requirements are low (see the MS spreadsheet calculator) and the capacity requirements are high you may well be OK, but you would need to be careful on how you carve up the MSA.

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(in reply to sabel9579)
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RE: Raid 5 vs. Raid 10 - 10.Aug.2011 2:48:36 PM   
sabel9579

 

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Mark,

Thanks for the feedback. I have a follow up. The MSA70 is attached to a DL380G7 server that currently has 8 disks that are not in use. would it be better if I configure the db's using those 8 disks (either raid 5 or 10, leaning towards 10) and use the MSA for something different (restore LUN's)?

Thanks!

(in reply to mark@mvps.org)
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RE: Raid 5 vs. Raid 10 - 17.Aug.2011 3:42:36 PM   
sabel9579

 

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Bump to anyone that can provide some insight

(in reply to sabel9579)
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RE: Raid 5 vs. Raid 10 - 17.Aug.2011 5:13:06 PM   
travis.sheldon

 

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If you are going to use RAID and you need larger than 2TB 'arrays', then I would recommend RAID 10. I currently have a server with 3.5k users with an average mailbox size of 5GB running off RAID 1 SATA drives with very little latency..it's all a matter of your requirements. Exchange 2010 was designed to take advantage of the single disk solutions and SATA solutions, so your biggest concern in my eyes will be growth and expansion..I haven't come across anything that demanded better IO performance than what my SATA drives provided.

For instance, if you chop the MSA as RAID 10 with 8x 300GB SAS, you're going to have ~1200GB of storage (If my math is correct) .. if within a year your database(s) total over 1TB, you're going to have to expand with more drives..eventually, you may hit the ceiling with being at complete capacity. With larger databases that dont have size limitations, it's a lot harder to expand to a different solution or to move databases.

I've noticed better performance from using multiple drive sets, IE, 4x 300GB RAID1. I'm not familiar with HP MSA so I'm not sure of the limitations of the storage device in terms of number of RAIDs, so if they only allow under 4 arrays, then you're only left with RAID 5 and 10.

I have two 2010 mailboxes servers in another network connected to Dell Powervault MD1000 servers via SAS, each has roughly 15 SATA drives. The first one that I deployed I used RAID 5 for the benefit of larger capacity and within 6 months I had to deploy the second server because of performance issues and databases breaking. The second server I deployed had RAID 10 and I've yet to have a problem.. I had to double my drive size to make up for the lost space between RAID 5 and 10, but I'll never look back at RAID 5 for >= Exchange 2007. This network needed both decent/good performance on IO, but more capacity than performance as it's a blind archive server.

(in reply to sabel9579)
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RE: Raid 5 vs. Raid 10 - 17.Aug.2011 5:20:47 PM   
sabel9579

 

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Thanks Travis!! You basically sealed it for me. the MSA has 25 slots all filled with 300 gb SAS drives. I only manage about 1700 users all with mailboxes between 350mb and 1GB. I believe I will have plenty of space and the 8x300 scenario will work well I believe. I figure I can create 2 or 3 LUNS but only use one of them to start off. If my DB's start growing too fast too quick I can simply add another LUN and more space

(in reply to travis.sheldon)
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RE: Raid 5 vs. Raid 10 - 17.Aug.2011 5:30:01 PM   
travis.sheldon

 

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Sounds like you have a good plan :) only thing to consider is if there is/will be a DAG implemented as you'll have to mirror the database layouts across the LUNs of the DAG member, (ie, you put the databases on drive D, E, F on MBOX1, server MBOX2 needs to have the same layout, drives D, E ,F available)...the DAG is the only thing that I've seen raise IO, but on my 3.5k network it wasn't noticeable enough to worry, and all of my users are remote (none are in the local network of the Exchange network)

I would start off with 2 LUNs with either 2 or 4 databases spread between them..if you then see the need to expand, you can create a new LUN and database and perform online moves to the new database for users.

I always recommend keeping the DBs to 40% of the LUN capacity just in case you ever have to run eseutil on the DBs.

(in reply to sabel9579)
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RE: Raid 5 vs. Raid 10 - 17.Aug.2011 5:42:20 PM   
sabel9579

 

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Much appreciated Travis. Thank you!

(in reply to travis.sheldon)
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