On Wed, Mar 19, 2008 at 11:46:17AM -0400, Damon L. Chesser wrote: > Alex Samad wrote: >> 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 > 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 HP Storeage works support mutlipathd - with their HBA (qlogic) and their eva (and I think XP ) range
and they are moving towards using the standard drivers, not having to
install their own
> 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
Storeage works have a whitepaper on doing multipath with linux and their
storeage, using multipathd
> 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.
>
> 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
> [EMAIL PROTECTED]
>
>
>
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--
His mind is like a steel trap: full of mice.
-- Foghorn Leghorn
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