Matt Jacob e770bc6bf5 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		2007-02-27 04:01:58 +00:00
..
geom_apple
geom_bde
geom_bsd
geom_cache
geom_ccd
geom_concat
geom_eli
geom_fox
geom_gate
geom_gpt
geom_journal
geom_label
geom_mbr
geom_mirror
geom_multipath	First cut at GEOM based multipath. This is an active/passive{/passive...}	2007-02-27 04:01:58 +00:00
geom_nop
geom_pc98
geom_raid3
geom_shsec
geom_stripe
geom_sunlabel
geom_uzip
geom_vinum
geom_vol_ffs
geom_zero
Makefile	First cut at GEOM based multipath. This is an active/passive{/passive...}	2007-02-27 04:01:58 +00:00
Makefile.inc