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Need optimal RAID configuration for existing hardware for Exchange 2010 install

Posted on 2011-09-19
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I have (2) new Dell R510 servers to be used for Exchange 2010.  I will have the mailbox, CAS and HT installed on both servers and will configure DAG.  Currently have about 750 mailboxes at a total size of under 100GB.  Each server has (2) 146GB 15k SAS drives and (10) 1TB 7.2k SAS drives.  I know I will use the (2) 15k drives in RAID 1 for the OS/Exchange, however I want recommedations on the optimal configuration for the rest of the setup.  Should I put the logs on this 15k RAID 1 as well?  Should I do multiple RAID 1's and put the DB/Logs on them together, breaking the mailboxes up into 4 or 5 different DB's?  Should I do 1 large or 2 smaller RAID 10's?  Should I keep some of them for hotspares and not use all 10?  

Experts, please provide your optimal setup with this existing hardware.
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Question by:wpstech
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by:Miguel Angel Perez Muñoz
ID: 36560192
I´ll do this:

OS > 15K SAS drives
Database(s) > 6 RAID 5 drives
Transactional logs  > RAID 1 2 drives
Hot spare 2 drives.

I think that 6 drives on RAID 5 provides good I/O to disk operations. If need more space, can make RAID with 7 disks and get only one for hot spare.

Database segmentation depends of your planning. I using departamental databases and schema runs well.
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Author Comment

by:wpstech
ID: 36560275
everything i've read and know leads me to believe that RAID 5 w/ 7.2k drives would not be a good choice, so I wasnt even considering RAID 5 for that reason.  With that said, I also want input on how the 2nd server should come into play in this Ex 2010 scenario...should it only be a passive box holding only the passive copies in the DAG?  Should I split the DB's according and put half live on one and half live on the other and split the passives between the 2 as well?  Chime in experts...I have this new hardware in hand and ready, but am not familiar enough with all of the new changes in 2010 to comfortably make the decision that I think would be optimal
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by:wpstech
ID: 36569064
bump...advice/recommendations/opinions please!
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by:gsmartin
ID: 36569750
RAID 1 is standard for OS and Application drives, RAID 5 is standard File and General Purpose, RAID 10 is standard for Databases, Transaction Logs, Exchange, etc...  RAID 5 is known for fast Read Access and single drive failure redundancy, RAID 10 is known for Fast Write Access and Better drive redundacy (supports multiple hot spares);

I recommend RAID 10 for the Exchange Database (Information stor) and transaction logs.  Note the more spindles the better the RAID 10 performance.  Given the number of drives, speed, and size I would recommend a single RAID 10 array with 2 hot spares.  Typically with RAID stripping the more Spindles the better to increase IOPS.  Then create multiple drives within the RAID 10 set to divide the databases and transaction logs.  Note either RAID 10 option will work and most likely see minimal performance difference given the separation of databases across they arrays.

FYI... Note their is a MS Exchange 2010 High Availability configuration using active and passive database copies that supports a RAID less drive (JBOD) configuration.  This configuration uses multiple drives and Exchange servers to divide Exchange databases and logs files.  Given the Active/Passive database and lag copies the High Availability/Redundancy is strictly at the database level (using database replication) vs the old storage RAID level redundancy (Note this requires at least 3 or more Exchange servers).

Note: This is the configuration we are using internally with 4 Exchange 2010 servers split across two data center sites.  My initial Exchange design was to breakout the CAS, HT, and DAG roles (2 CAS/HT and 3 DAG servers), but I ended up rearchitecting and collapsing all services on two 4 Exchange servers making them all equal with the exception of one acting as a lag copy (extended transaction log history as a restore point).  Further, we are also leveraging our load balancer to manage the inital Exchange traffic.  This is may or may not be a good option for your environment, but something to consider.  In our tests we can shutdown multiple Exchange servers without users experiencing an Exchange outage.

Below is some very good Exchange and RAID Reference Material to consider:
http://technet.microsoft.com/en-us/library/ee832791.aspx
http://technet.microsoft.com/en-us/library/ee832792.aspx
http://technet.microsoft.com/en-us/library/ee832794.aspx
http://blogs.technet.com/b/exchange/archive/2010/03/29/3409629.aspx
http://searchstorage.techtarget.com/tip/Determining-the-number-of-drives-in-a-RAID-group
http://blogs.technet.com/b/exchange/archive/2009/11/09/3408737.aspx
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by:gsmartin
ID: 36569819
Additional note: Depending on the configuration you choose for the most part, Microsoft recommends for Exchange 2010 a single LUN for both database and log file.  Spreading multiple databases with log files accross independant LUNS.  (e.g. 4 Databases each with a Log file on to 4 separate LUNS/Drives - log file remaining with the respective database.)  
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Author Comment

by:wpstech
ID: 36574848
We are limited to the 2 servers that I've described above, with the exception that I would like to deploy DAG so we'll have a 3 non-exchange server act as the witness.  So you're recommending that I use 8 of the 10 7.2k SAS drives in RAID 10 but are you suggesting that I create 1 RAID 10 with all 8 disks or that I create 2 RAID 10's, each w/ 4 disks.  

I dont completely understand how failover works with DAG so I want to ensure that I build the RAID and deploy the databases and logs in the most optimal scenario considering DAG...basically, so that I can take advantage of rolling over to a passive copy for as little of the mailboxes/databases as necessary in the event of an issue...

 
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by:gsmartin
ID: 36575643
Note the Exchange witness file's intended purpose is in a multi-site environment.

In my case, where the witness file sits on a file server at remote site apart from the DC and DR Exchange servers. The Exchange 2010 servers manages connectivity and active Exchange databases for the DAG cluster to ensure the server controlling the active database is still up and locking the witness file.  If the connectivity between the data centers go down the passive database servers checks to see if the witness file is available or still has the file locked by the active database Exchange server(s) through another connection.  This is typically implemented in a 3 or more Exchange DAG cluster configuration. Otherwise even though it's part of the base install it's not required.  

DAG uses log shipping to ship logs (replicates databases) between DAG members.  The redundancy aspect is now you have additional database copies across multiple servers.  Therefore, in a 3 plus server environment you technically no longer require backing up your Exchange servers given that you have multiple copies of the database.  In my case, I have 3 copies that are in line with each other and a 4th DAG server that has a lag (extended) copy of the log files.

Anyway, the truth of the matter is given the number of drives you have you technically can go either way with 1 or 2 RAID 10 LUNs.  Without really knowing the Exchange database server load can't determine exactly what is going to yield the best performance.  On a 2 LUN RAID 10 array, splitting the database across 2 LUNs may provide some benefit, but again the more spindles the better in terms of IOPS performance.  So without benchmarking it can go either way logically; having said that, I still stand by recommending a single RAID 10 array configuration 8 + 2 hot spares.
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Author Comment

by:wpstech
ID: 36580001
what are your thoughts on using multiple RAID 1's and dispersing the databases and logs across them?  I've read several documents, one particular was a case study/recommended deployment guide from Dell, where they recommending using 8 drives to build 4 RAID 1's, then splitting the mailboxes into 4 databases, putting one on each RAID 1 along with it's transaction logs.  This setup still allows for 2 drives to be left as hot spares.  Keep in mind that I want to take advantage of a DAG configuration as well.

What are your thoughts on this vs. the single RAID 10 setup?  Thank you for all of your opinions/recommendations, I just want to better understand what is going to work best with Ex 2010 and DAG, since both are new to me.

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by:wpstech
ID: 36580411
also, if I go with the single RAID 10 w/ 8 disks how should I configure the volumes for the databases and logs?  Since I keep reading that with Ex 2010 I should now put the DB/Logs together, should I do something like this:  Create 4 volumes (let's just say Volumes D, E, F and G) and then break out the mailboxes into 4 databases, placing one database and its respective logs onto each of these 4 volumes?
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Author Comment

by:wpstech
ID: 36580921
actually, now I'm thinking that perhaps the best option would be to create (2) RAID 10s, each using a total of 4 physical disks (1TB 7.2k SAS) and using (1) RAID 10 for databases and using (1) RAID 10 for logs.  This will allow for (2) independent RAID 10's and it will keep the databases and logs on separate physical disks
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by:gsmartin
ID: 36581844
Ok, here is some interesting information.
As we know, the bottom line is:  What is the overall IOPS performance that you can yield from 7.2 RPM SATA drives, correct?    A single 15K SAS drive has an average of 175 IOPS, where as a single 7.2K SATA drive has an average of 75 IOPS.   (Note these are only averages, actual IOPS varies between drive manufactures).  So, SATA drives are about 57% slower than a single 15K SAS drive.

Now given that, single RAID 10 with (4) 7.2K SATA drives x 75 IOPS = 300 IOPS.  This is roughly equivalent of a single 15K Fiber Channel drive that averages 200 to 300 IOPS.   Additional note:  RAID 1 and RAID 10 will cut that number to little more the half yielding 30 to 40 IOPS per drive; due to the RAID IO hit penalty, which is 2 writes for RAID 10 vs. 4 for RAID 5.  This to me is going to be the biggest issue.

This information should help put everything into perspective.  What you are running into with this configuration is your trying to squeeze as much performance as possible out of the hardware you already have vs. determining the performance you would like to achieve before buying the hardware.

Your primary objectives when implementing the new Exchange 2010 environment should be at the least performance and redundancy, especially when you need to plan for 750 users’ mailboxes.  What you have run into is the drive size and type doesn't meet the performance needs on the Exchange environment.  Don't take this the wrong way, because sometimes you don't realize these things until you dig into the numbers.

Anyway, given your hardware a single RAID 10 is still going to give you the better IOPS this way all database can take advantage of the additional IOPS, but ultimately it would be preferred to do it with faster drives for Exchange purposes to yield event much greater performance.

And to your last question:
"Create 4 volumes (let's just say Volumes D, E, F and G) and then break out the mailboxes into 4 databases, placing one database and its respective logs onto each of these 4 volumes?"

Yes, this would be the best way to go.  


References:
http://www.yellow-bricks.com/2009/12/23/iops/
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Author Comment

by:wpstech
ID: 36583375
thanks again for all of your comments, I really appreciate it.   To better clarify a few points, the drives I have are 7.2k nearline SAS, which should be better than the SATA specs you've provided here.  

Secondly, as the title of the question states "for existing hardware", this is the result of me being a brand new employee and being tasked with the Ex 2010 migration where hardware was already purchased.  This is not hardware that I purchased without doing the proper planning in advance.  

Also, I've recently checked and the current database size is actually even much smaller than I originally stated.  For all 700+ mailboxes the total combined DB size is only around 40GB.  While I do anticipate this size increasing as we likely will increase the allowed mailbox size for all users, it does seem wild that I have (10) 1TB disks available for mailboxes and logs for only 40GB worth of mailboxes.  

With that said, your final recommendation is that I should build a single RAID 10 w/ 8 drives rather than build 2 RAID 10s with 4 drives each (1 for databases and 1 for logs, like I would have done w/ older versions of Exchange)?  And regardless of the RAID setup, you recommend that I should create multiple volumes and spread the databases and their logs across these volumes, keeping the logs on the same volume as their database?

Please confirm.  Thanks again.
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by:gsmartin
ID: 36584152
I've been your situation before, so I know where you are coming from.  Besides, most of us don't often have the time to do indepth research to due to other projects and priorities.  So, I didn't mean anything personal by the comments.  I am not always able to build test environments to implement solutions.

The average IOPS for nearline from what I've seen was 75 to 100 IOPS, but typically always have been referenced on the lower side at about 75 or 80 IOPS.  7.2K standard SATA has been referenced at about 60 IOPS, again this doesn't factor the RAID IO hit, which cuts the overall numbers in half.

Recommendation:  Build a single RAID 10 with 8 drives plus 2 hot spares.  Partition the drive equally into 4 partitions (D, E, F, G) .  With (4) Exchange databases and log files; each partition should contain 1 database and it's respective log file.    Just as a confirmation, I confirmed this recommendation with my Microsoft Exchange vendor who assisted in completing our Exchange 2010 server architecture; and they validated my recommendation of the single RAID 10 due to the higher IOPS.  

Note when Exchange has to work hard and run various read/write tasks, RAID 10 with alot spindles will be able to provide the better performance for the database(s) requiring it; smaller RAID 10 sets won't.  Therefore, it's better to pool the drive resources, becuase the demand(s) between the database will vary.  
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gsmartin earned 500 total points
ID: 36585270
REWRITE: Had to clean up some of the bad verbiage...

I apologize for my tone in original comments. My objective is to help and not scrutinize people’s skills, environments, and situations.  We are all here to collaborate and fill in each other’s gap in experience; where applicable.

In any case, the average IOPS for nearline SATA, from what I've seen, was 75 to 100 IOPS, but typically this has been referenced on the lower side at about 75 or 80 IOPS.  7.2K standard SATA has been referenced at about 60 IOPS; again this doesn't factor in the RAID IO hit, which cuts the overall performance numbers down to more than half.

Recommendation:  Build a single RAID 10 with 8 drives plus 2 hot spares.  Partition the drive equally into 4 partitions (D, E, F, G).  With (4) Exchange databases and log files; each partition should contain 1 database and it's respective log file.    Just as a confirmation, I confirmed this recommendation with my Microsoft Exchange vendor who assisted in completing our Exchange 2010 server architecture; and they validated my recommendation of the single RAID 10 due to the higher IOPS.  

Note when Exchange has to work hard and run various read/write tasks, RAID 10 with a lot spindles will be able to provide the better performance for the database(s) requiring it; smaller RAID 10 sets won't.  Therefore, it's better to pool the drive resources, because the demand(s) between the databases will vary.  
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Author Closing Comment

by:wpstech
ID: 36586854
thanks so much for all of your help, i appreciate your insight.  

another item that I completely forgot about is that they are also using GFI MailArchiver, so I dont exactly know how that will play into all of this.  I dont know if that is the reason why the database size is so small (around 40GB) because possibly they the policies in place to reduce the databases by removing old messages since they are in the GFI databases...i'm not sure, I'll have to look further into this...

again, thanks for the insight and for confirming what I think is the best storage setup for the hardware we have available.
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by:gsmartin
ID: 36591426
It's recommended to have GFI on it's own server, apart from Exchange.  So there won't be a direct impact, but it will add more load on Exchange.
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