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March 04, 2005

V880 and AP

I had to spend some time earlier in the year investigating an interesting Unix problem (well at least I thought it was interesting - the rest of you may be bored witless by it). Sun Microsystems make an interesting server called the V880. which uses internal FCAL disks (instead of the more traditional SCSI arrangements). These disks can be attached to dual rings so that there are two hardware paths to each disk - an arrangement which helps with disk access (you can read from either controller) and with redundancy (the failure of a controller does not mean loss of access to a disk). Ideally the disks can be mirrored across backplanes which results in four paths to each filesystem and no common point of failure.

So much for the theory, how about the practice? Well, out of the box, you can see each disk twice - what you need is a meta-layer to create a common access point. In Solaris versions 6, 7 and 8; this is done with the AP package. Whack on the package, follow the instructions and Bob (or possibly Bert) is your uncle.

What about Solaris 9? Well that is the source of my problem - the AP package will not install under Solaris 9 and the official Sun solution is to use a Veritas solution (which costs money). Most customers are not real impressed by the suggestion that they spend money so what other solutions are there?

Well it turns out that what you need is the SUNWsan package set. The documentation for this specifically states that it is for *external* enclosures (like the 3300 storage boxes) but it turns out that the 880 fibre rings look like external storage to the software. So whack on the software (following the instructions for an external 33xx array) and do the normal discovery - lo and behold you will see the two controllers and you can then (still following the 33xx instructions) set up dual path names. Make sure you are working on a terminal with cut and paste because the path names are going to be really, really, really long.

Bonus tip: normally SDS (SVM) can work out path names - you can use c0t0d0s0 and the software knows that you actually meant /dev/dsk/c0t0d0s0. In the case of SUNWsan devices, this does not work. Use the full path names or you will get many, many, many error messages (that was the voice of bitter experience).

Posted by Ozguru at March 4, 2005 06:00 AM

Comments

Posted by: Rofl at March 4, 2005 06:03 AM