Raid1 vs Raid5 Microsoft exchange data

5 pts.
Tags:
EMC
Microsoft Exchange
RAID
RAID 1
RAID 1 vs RAID 5
RAID 5
SAN
Storage
We are implementing Microsoft Exchange on a EMC DMX3500 DASD Subsystem that has 146GB and 300GBs. Talked to Gartner Group Consultant Bob Passmore and he is strongly recommending RAID 1: his justification is based on the fact that RAID 1 is double the number of disk drives; therefore you cut what is called QUEUE DEPTH of the data path in half which will significantly help performance. Exchange data is small blocks of data; short I/O burst and RAID 1 will work a lot faster. With RAID 5 you are spreading the writes across multiple drives; however, it is to fewer drives and the QUEUE DEPTH is significantly increased even in normal I/O activity. You asked what Queue depth is: it is the number of I/O operations that can be run in parallel on a device. It is usually possible to set a limit on the queue depth on the subsystem device driver (SDD) paths (or equivalent) or the host bus adapter (HBA). Also general recommendations are to utilize Raid 1 for transaction log files SMTP queues and MTA queues. After Exchange Server's databases and transaction logs, the resources that consume the highest number of disk I/Os are queues. Exchange Server uses two different queues: the MTA queue and the SMTP queue. MTA queues are used as a temporary message repository for messages received from Exchange 5.5 servers, or for messages that arrive via an X.400 connection. MTA queues are also used to temporarily store messages that arrive while a mailbox is being moved. SMTP queues handle inbound and outbound SMTP messages. Whether or not you decide to group the SMTP and MTA queues together, they need to be placed on a dedicated partition. Microsoft recommends a SAN-based RAID 1 volume. Some administrators have been known to cut corners and not use a dedicated volume for the SMTP and MTA queues. If you decide that you don't want to use a dedicated volume for Exchange Server's queues, then it is extremely important that you don't place the queues on the same volume as the Exchange databases or transaction logs. And finally; the storage vendor that we are utilizing toady EMC is recommending RAID1 for Microsoft Exchange data. Would you agree with the above statements. My management want to place Exchange on RAID 5.
ASKED: April 30, 2008  2:31 PM
UPDATED: May 1, 2008  1:36 PM

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Hi Bobc – RAID10 is definitely what’s recommended for Exchange. Have a look at: http://msexchangeteam.com/archive/2004/10/11/240868.aspx for more information.

David

—————–Blithespirit——————

look at the IO’s of the data

Raid five has 5 disk writes to raid 1 having 2.

Raid 1 is faster for writes and offers better protection as well and resilience in event of failure.
Raid 5 is a reasonably priced resilience model based of reduced performance in the event of a disk failure.

—————-

Raid 1 is expensive and raid 5 is cheaper but raid 1 offers better performance at a higher cost

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  • Wrobinson
    There is more than meets the eye here. RAID-1 is recommended for transaction logs and queues because of heavy write activity. The Exchange databases typically perform more read than write activity, so the speed sacrificed using RAID-5 is not as impactful and the positive trade-off in terms of capacity and ault-tolerance is often desirable. There is specific guidance on Exchange storage design considerations for Exchange Server 2003 and Exchange Server 2007 on TechNet. You should check the following references as starters (see: http://technet.microsoft.com/en-us/library/bb125079.aspx and http://technet.microsoft.com/en-us/library/bb124518.aspx).
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