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If you have 2 raptor 10k rpm drives in Raid0, can you add another sata (7200prm) drive outside of the RAID or would it have to be inside the RAID?

What would be the consequences of adding a 7200 RPM drive to the raptor 10k rpm RAID0 besides the I/O speed going to 7200rpm.

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3 Answers

Assuming your SATA card has enough ports then you can add it outside the RAID. Oh and don't mix disk types in RAIDs - bad idea, bad ;)

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Can you expand on why you don't mix disk types? –  Jim Mar 26 '10 at 13:47
    
Isn't I\O speed going to 7200 reason enough ? –  Jimmy Mar 26 '10 at 13:55
    
+1 for not mixing drives. Some seem to say OK but any training I had from HP or IBM said not to mix. –  Dave M Mar 26 '10 at 14:01
    
@Jim because RAIDed disks are written to in parallel, and if they are "out of sync" on writes (due to RPM, size, model etc) one will always be working to "catch up" to the other - suboptimal resource use. This could possibly result in early failure for the slower disk, but even if it doesn't you'll have one disk idling for half its life. –  Andy Mar 26 '10 at 14:06
    
You can mix size (though it's a waste, and the "new" drive has to be larger) but not speed. A really good RAID controller might be able to compensate for the fact that 1 drive is 25% slower, but I wouldn't bet on it. –  Satanicpuppy Mar 26 '10 at 14:57
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First, many hardware RAID solutions (and all software RAID I know about) will let you add a single disk beside an existing set. You can think of a single disk as a one disk RAID0.

Whether or not you can add a disk to a RAID0 set depends on the RAID implementation. An individual hardware RAID card may not let you do it, some might. As for mixing and matching disk speeds, you're going to be limited by the 7200 RPM. It's hard to say exactly how much slower as it depends on the workload. It'll still be faster than a single 10K or a single 7200 RPM disk, but slower than 3 10K disks.

If you post more details about your setup (RAID controller, how many SATA/SAS ports you have, etc) I can give more specific answers.

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As long as there is another controller port open, you can almost always add another drive in this way.

"best practices" would say don't mix drive speeds, but there is absolutely no reason to fear doing so.

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