Thanks Gordan! You put me to the right direction. Yes, we are driving an active/passive solution. Each node can see the storage LUNs of both nodes on startup. We sort them in an init script within the initrd (remove and re-add) to get a well-defined order. Then we start multipathing via vpath. Afterwards, we start root-raid1 via MD, then we mount the root fs and go on booting. This is what we did for the last 4 years. Driver-based multipathing was our first trial, before we found the current solution, but our colleagues rebelled. Therefore RDAC/vpath. Makes up for a big fat initrd, though. But ok, techniques evolve, and today dm-multipath is a supported solution. DRBD is unknown land for me. But it's really promising. The drawback is a resync when one node boots and longer resync times. (..if it works as I guess. link to documentation highly welcomed) We will see how this biest works when FC-communication fails on one or both nodes. > > I still have a third opportunity. I can use Qlocig's driver-based > > multipathing and keep using host-based mirroring instead of > > using dm-multipath, which currently prevents me from setting up > > raid-devices as root-fs. > > I'm still not sure how all these relate in your setup. Are you saying > that you are using the qlogic multi-path driver pointing at two > different SANs while the SANs themselves are sorting out the synchronous > real-time mirroring between them? No, both qlogic HBAs do see both Storage controllers via their own SAN. There are two switched SANs, crossovered for fault-tolerance, but else autonomous. (don't ask how) The driver does multipathing over both HBAs, so we see the same controllers/LUNs once instead of twice. But we don't use this anymore. It worked ok, though. Mirroring disk partitions from controllerA to controllerB was always done by MD-raid1. (simple&good) > > > Well, that will work, but is somewhat ugly. > > > > So far, I had only a short glimpse on OSR. I think I will need > > to dive deeper. > > It sounds like you'll need to add support for qlogic multi-path > proprietary stuff to OSR before it'll do exactly what you want, but > other than that, the idea behind it is to enable you have have a shared > rootfs on a suitable cluster file system (GFS, OCFS, GlusterFS, etc.). As far as I understood, no. I need to do multipathing and mirroring. Whether I do it by dm-multipath and MD-raid or by QLA-Multipath and DRBD, or any other combination, doesn't change the result. It only changes the way the whole thing behaves in case of a failure. Actually, I hope to be able to start a DRBD device in the initrd and mount it as root. That is the first hurdle to be taken. The rest is nice-to-have. > It's generally useful when you need a big fat initrd > to bootstrap things such as RHCS components, block device drivers > (e.g. DRBD), or file systems that need a fuller environment to start up > than a normal initrd (e.g. GlusterFS, things that need glibc, etc.). Nice-to have. I am glad to know there is such a thing. When we started, there was nothing. I will report back when I have some results. Thanks for your help! Thomas -- http://www.openstreetmap.org/?lat=47.172&lon=7.4395&zoom=15&layers=B000FTFTT&mlat=47.16677&mlon=7.43513 Jetzt kostenlos herunterladen: Internet Explorer 8 und Mozilla Firefox 3.5 - sicherer, schneller und einfacher! http://portal.gmx.net/de/go/atbrowser -- Linux-cluster mailing list Linux-cluster@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cluster
