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SamC
White Water Yakist
3467 Posts |
 Posted - 2003-05-22 : 16:21:03
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| If I downgrade my dedicated server from a 3 disk RAID 5 to a 2 disk RAID 1, how much of a performance hit should I expect?Sam |
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JimL
SQL Slinging Yak Ranger
1537 Posts |
Posted - 2003-05-22 : 16:49:07
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| I would not even be conserned about the performance issue.Going to Raid 1 removes you auto redundency and Hot Spair rebuild online capability. On Most Raid arrays if the primary of a Raid 1 config fails the system will crash.JimUsers <> Logic |
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SamC
White Water Yakist
3467 Posts |
Posted - 2003-05-22 : 16:57:51
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| Thanks Jim,I was concerned that there might be a performance problem. I hadn't heard about the system crash on primary failure though. Wasn't RAID 1 designed to allow nonstop replacement of a failed disk?Here's a pretty good website that discusses RAID.Sam |
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MichaelP
Jedi Yak
2489 Posts |
Posted - 2003-05-22 : 17:21:24
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| Sam,I think your reads will be slower, but writes should be faster. You will also lose some storage space. I don't think there is any way to easily convert your existing RAID 5 into a RAID 1 array. I think you'll haev to create the RAID 1 and copy over the data from the RAID 5. Jim has a good point about the system "stopping" until you fix the dead disk. I think it depends on your RAID controller and how you have it setup. I think many of them have a "What do I do if this happens" setting.Michael<Yoda>Use the Search page you must. Find the answer you will.</Yoda> |
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chadmat
The Chadinator
1974 Posts |
Posted - 2003-05-23 : 12:07:56
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| I don't think either would be faster. With RAID 5 you have 2 disks reading/writing data, and one writing parity. With RAID 1 you only have one reading/writing, and one mirroring. RAID 1 is great for T-Log, becasue T-Log writes are sequential, but for data it isn't good.I would keep the RAID 5 array.-Chadhttp://www.clrsoft.comSoftware built for the Common Language Runtime. |
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aiken
Aged Yak Warrior
525 Posts |
Posted - 2003-05-27 : 14:33:22
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| Any modern hardware-based RAID 1 solution is fine if either disk goes away; the logical drive is made up of the two physical drives, and neither one is "primary".If you're talking about plain old RAID 5, I think your performance will be slightly better. In a 3 disk RAID 5 array, you have two disks with data and one disk with parity. The two disks will be used for reads, but writes will involve 2 writes and 1 read (write to disk 1, read from disk 2, calculate parity, write to disk 3).In the two disk RAID 1 scenario, reads will still come from two disks: RAID controllers are smart enough to know that if you want a bunch of data, it's more effecient to read half from one disk and half from the other. Writes will be a bit faster, as there's no read/write penalty.However, I'd expect that the difference wouldn't be significant or noticeable. I'd worry much more about having the log and data on the same array, if that's the case -- that's a real performance killer.Cheers-b |
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RAID performance question