Convert simplex array to duplex

[CA1411553]

My DL380 G3 is running has 6 internal drives running on a SA6402 in "simplex" mode. With a terminator I can use both channels to run the 6 internal drives in "duplex" mode.

I'm not finding much on simplex vs duplex. If I use duplex I can tell that 3 internal drives will run on each channel.

Will it be possible to have the same 6 disk logical array if the disks are on 2 channels or will I have to delete and recreate the array and restore from a backup?

Thanks!

[Chris Rosan]

From what I understand with smart array, you can move the drives around, BUT as with anything like this you should do a FULL system backup, and test the backup before you change anything.

From memory, if the 6 drives are all part of one logical drive, then I don't think you'll see an advantage as the i/o has to traverse across the card to the other channel, rather than just drive to drive.

If the drives are a seperate logical drive, then you should. EG I run my MSSQL servers with DB's on one set of drives on one channel, & OS & Logs on another set of drives and channel. I read it improves performance (and it seems to), but that is with 2 seperate Raid's.

[CA1411553]

Thanks for the reply.

Since the 6402 can transfer 640mb/s total with 320mb/s per channel I would have thought that spanning a single array over 2 channels would provide a performance increase.

Since there are only 6 drives in the cage I feel 3 drive raid arrays use too much overhead for me to go the with that; 33.33% overhead with 3 drives vs 16.67% for 6.

Know any good tools to measure hard drive performance? I can test it out and see what the difference really is.

[CA1411553]

Oh wait a sec. With my poor eyesight I didn't realize that it isn't 3 drives on each channel with duplex, it's 2 drives on one channel and 4 on the other with the cage.

Obviously the intent is to have the OS mirrored on the first two drives and the data on a raid with 4 drives. That's 25% overhead on the raid 5 array which isn't as bad.

[Chris Rosan]

Then I would say you'll need to start from scratch again.

I had to do something similar to this with a server about 6 months ago when we were putting more drives in it. I purchased new drives, then one weekend I installed it & set the machine up, sunday night put the old drives back in and completed the job the next weekend. Worked really well, just make sure you label which drive is which, just in case.