From 05b92097cb751ac3e6ba126eed272f954f9c7210 Mon Sep 17 00:00:00 2001 From: mjacob Date: Tue, 27 Feb 2007 04:01:58 +0000 Subject: First cut at GEOM based multipath. This is an active/passive{/passive...} arrangement that has no intrinsic internal knowledge of whether devices it is given are truly multipath devices. As such, this is a simplistic approach, but still a useful one. The basic approach is to (at present- this will change soon) use camcontrol to find likely identical devices and and label the trailing sector of the first one. This label contains both a full UUID and a name. The name is what is presented in /dev/multipath, but the UUID is used as a true distinguishor at g_taste time, thus making sure we don't have chaos on a shared SAN where everyone names their data multipath as "Fred". The first of N identical devices (and N *may* be 1!) becomes the active path until a BIO request is failed with EIO or ENXIO. When this occurs, the active disk is ripped away and the next in a list is picked to (retry and) continue with. During g_taste events new disks that meet the match criteria for existing multipath geoms get added to the tail end of the list. Thus, this active/passive setup actually does work for devices which go away and come back, as do (now) mpt(4) and isp(4) SAN based disks. There is still a lot to do to improve this- like about 5 of the 12 recommendations I've received about it, but it's been functional enough for a while that it deserves a broader test base. Reviewed by: pjd Sponsored by: IronPort Systems MFC: 2 months --- sys/modules/geom/Makefile | 1 + sys/modules/geom/geom_multipath/Makefile | 8 ++++++++ 2 files changed, 9 insertions(+) create mode 100644 sys/modules/geom/geom_multipath/Makefile (limited to 'sys/modules') diff --git a/sys/modules/geom/Makefile b/sys/modules/geom/Makefile index 011ff4c..26e2209 100644 --- a/sys/modules/geom/Makefile +++ b/sys/modules/geom/Makefile @@ -12,6 +12,7 @@ SUBDIR= geom_bde \ geom_label \ geom_mbr \ geom_mirror \ + geom_multipath \ geom_nop \ geom_pc98 \ geom_raid3 \ diff --git a/sys/modules/geom/geom_multipath/Makefile b/sys/modules/geom/geom_multipath/Makefile new file mode 100644 index 0000000..d036fe0 --- /dev/null +++ b/sys/modules/geom/geom_multipath/Makefile @@ -0,0 +1,8 @@ +# $FreeBSD$ + +.PATH: ${.CURDIR}/../../../geom/multipath + +KMOD= geom_multipath +SRCS= g_multipath.c + +.include -- cgit v1.1