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How many RAID "Channels" are on the PERC H700? 2? How would I verify which RAID is on which channel, and can I move them from one channel to another to balance the load per channel better?

AX1
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2 Answers2

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From what we know of your environment you don't have enough disk-drives to worry about load-balancing. As Chris S said, SAS is different than SCSI in which there is one connection (channel in old school SCSI lingo) per drive. You have 6 drives, and a total of 8 connections to connect them to. You're already getting the maximum parallelism you're going to get out of the system.

Where this kind of thing can come into effect is if you're using SAS Expanders. The H700 can connect to up to 8 of those expanders (probably). Those expanders in turn can contain up to 25 drives in them. If you were pushing this card to the limit like that, you'd want to make sure your RAID volumes were striped across the enclosures (example: disks 1-5 in each enclosure are in a single RAID set for a total RAID of 40 drives), as that would leverage the exact parallelism that using multiple SCSI channels did in the pre-SAS days.

Community
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sysadmin1138
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  • Ahhhh, I knew I mixed up some incorrect information there. +1 for remembering me and my setup and taking that into account :) – AX1 Dec 19 '10 at 19:33
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I think you're stuck in old SCSI terminology. The PERC H700 uses SAS connections, which is one connection per drive; there are no channels like there were in SCSI.

The H700 Card has a single connector which fans out to 4 SAS drives. The H700 Onboard Chip has two 4x connections as aforementioned. I don't know if the card supports SAS Expanders.

Chris S
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