Alex Samad wrote:
Yes, the kernel does (or is able) to handle multipath, however AFAIK, the major SAN,NAS mfg do not support it. I only know of one former customer who tried to use it and it was failing. All the functionality you get from HBAs is not yet working. If you use multipath, you need to use vendor HBAs and vendor applications (aka PowerPath from EMC, the only one I have experience with) AFAIK. If you know better, please inform me. I did extensive searching on behalf of that customer and I only found that at best it is only partly running and buggy. This experience is about 6 months old.On Tue, Mar 18, 2008 at 04:37:30PM -0500, Ron Johnson wrote:-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 03/18/08 15:44, Mike Bird wrote:On Tue March 18 2008 12:56:00 Michael S. Peek wrote:But now I'm looking to build replacement servers and I thought I would ask what the community uses for it's hardware RAID, and why?We use "nothing" for hardware RAID. Software RAID is much more flexible. With hardware RAID you always need to have a spare controller on hand, because without a matching replacement controller you can't retrieve your data after a controller failure.That's what dual redundant controllers are for. Both transfer data for the same "device", and if one fails, the other keeps on plugging away. Obviously, performance suffers, but at least the machine keeps on chugging until you can replace the dead controller. Does Linux have that capability?I believe the kernel (+userland tools) can handle multipath (multipathd)SNIP
In short, IF multipathd works for your SAN/NAS you're home free, however, if you can't get it configured to see your LUNS, nothing you can do about it. So it comes down to which do you have more of? Time or Money? If time, play with multipathd, and if you have kernel devs on the team, perhaps you can fix the issues. If you have more money, go with the vendor solution.
Disclaimer, we are leaving the area of Linux I know the most about and are on the outside of my knowledge base. All I know of this subject is from that one customer I could not effectively help other then to say use EMC's application, even after extensive research by me. Even after going through all the howto's I could find, his SAN was not properly being displayed.
HTH Damon L. Chesser damon@damtek.com