How many RAID “Channels” are on the PERC H700

dell-percraid

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?

Best Answer

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.

Related Solutions

Dell PERC H700 – 3x RAID 1

According to the Dell documentation, the H700 integrated supports 0,1,5,6,10,50,60 and the modular supports 0,1,5,6,10. According to the technical guidebook, they both support a maximum number of 16 raid volumes.

Typically, when ordering Dell equipment, the configuration options do not necessarily reflect all possible configurations. However, if it is not specified, your RAID will not come preconfigured.

How to Over-Provision an Intel SSD RAID Array via Dell H700 PERC RAID Controller

You can use the Linux hdparm utility to set your provisioning parameters in this fashion:

root@ubuntu-10-10:~# hdparm -N /dev/sdb

/dev/sdb:
 max sectors   = 312581808/312581808, HPA is disabled

root@ubuntu-10-10:~# hdparm -Np281323627 /dev/sdb

/dev/sdb:
 setting max visible sectors to 281323627 (permanent)
Use of -Nnnnnn is VERY DANGEROUS.
You have requested reducing the apparent size of the drive.
This is a BAD idea, and can easily destroy all of the drive's contents.
Please supply the --yes-i-know-what-i-am-doing flag if you really want this.
Program aborted.

root@ubuntu-10-10:~# hdparm -Np281323627 --yes-i-know-what-i-am-doing /dev/sdb

/dev/sdb:
 setting max visible sectors to 281323627 (permanent)
 max sectors   = 281323627/312581808, HPA is enabled

root@ubuntu-10-10:~#

To give credit where it's due, I've got this info from a German server builder's website wiki.

But according to the Intel docs, it would be enough simply to keep the sectors in a "clean" state (in which they would be after a secure erase) by never writing to them. If you define a container/volume which only ever uses 300 GB of each of your drives, this is exactly what you are doing for half of your drives' sectors.

Best Answer

Related Solutions

Dell PERC H700 – 3x RAID 1

How to Over-Provision an Intel SSD RAID Array via Dell H700 PERC RAID Controller

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