Hello Goswin, On Mon, Jun 25, 2012 at 6:50 PM, Goswin von Brederlow <[email protected]>wrote:
> Ritesh Raj Sarraf <[email protected]> writes: > > > Do you see this affecting multipath? > > > > There is no use case to run dm-multipath on a local block device. > > Don't be too sure about that. I've been playing with dm-multipath on > local block devices because it has a timeout feature. If a single device > in a raid hangs (which can take up to several minutes till all the > resets on all levels have been tried before you get an error or may > actualy hang forever) you can use multipath to make it give up faster. > > I am still curious why you would want to run multipath on top of a local device ? You definitely want device mapper but multipath IMO. As for USB deivces, multipath highly recommends blacklisting local (which includes USB) devices. > > There are setups where you would want LVM on top of your SAN Multipath > > Device, but I think we already take care of that. > > Since multipath-tools doesn't provide any initramfs-tools scripts yet > I don't see how that could be. I think booting from a multipath device > isn't supported at all yet, right? > > It does. http://anonscm.debian.org/gitweb/?p=pkg-lvm/multipath-tools.git;a=tree;f=debian/initramfs;h=79f50dfee645e2dc72268a306099285bf0dc0b33;hb=HEAD We care to create the proper multipath maps in the initrd. > I can also imagine setups with a multipath SAN with LVM that and each LV > having a different multipath setup. E.g. LV1 uses path1 with fallback to > path2 and LV2 the other way around. > > Which would be asking for trouble for all your LVs are are served of a VG that resides on multiple maps. Your VG will hang/error out when only one of the maps go down. > Please let me know if you are expecting something else from multipath. > > One of the problems in current initramfs-tools is with devices that take > a long time to be detected. My experience with external enclosures was > that detecting the drives takes rather long, just like USB takes it > time. > Yes. The remote SAN devices have timing issues. And we try best to handle that situation. I still think that is not the use case you have. And if you have issues with a remote SAN device setup, please do report it. > > So I think that if you add support to boot from multipath then it would > definetly fall under the problem cases and need a local-block script > rather than local-top. > > Boot from multipath (i.e. Root on multipath) is a setup we support. It is documented in the README.Debian file. MfG > Goswin > > Thanks, Ritesh -- Ritesh Raj Sarraf RESEARCHUT - http://www.researchut.com "Necessity is the mother of invention."
