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I'm in the process of setting up a server. Dell PE R510, 6 450GB HD. It came with all drives RAID 5'd, I'm wanting to wipe the configuration and set 0 and 1 as RAID 1, then 2-5 as RAID 5. When I go to setup RAID 1, it's asking me about which Caching Policy to use - Read/Write, Write only, Read only, and none. I'm not sure which to pick here...suggestions? This server will be used for Exchange 2010 and the RAID 1 drives will be used for the OS and Logs, and the server will be on a battery backup. Thanks in advance.

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does your raid card have a battery backup? If not read only; If so your call on read only or read/write –  Lamar B Dec 7 '11 at 23:22

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up vote 3 down vote accepted

The RAID write cache policy should be set depending on the disk I/O load. You must make sure that you have a battery on the RAID controller and that the battery is functional.

The cache policy settings can be changed at any time from Dell OMSA.

I suggest to start with write caching disabled and only if you have problems with the I/O to change the write cache policy.

I would use RAID10 only instead of splitting that stuff in a RADI5 and RAID1 volumes.

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Why would you start with write cache disabled? –  ewwhite Dec 7 '11 at 23:23
    
Batteries fail. Power failures happen. Why introduce another hazard when I do not need it? I already have the FS cache inside the OS. Imagine having 100 servers, if I increase the chances for them to fail with only 1% this means that I have high chances for one to fail when I will have the next power failure. –  Mircea Vutcovici Dec 8 '11 at 14:26
    
Thanks, it's good to know I can change it after the fact! –  Don Dec 8 '11 at 15:12

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