diff options
Diffstat (limited to 'extras/multipath/README')
-rw-r--r-- | extras/multipath/README | 18 |
1 files changed, 8 insertions, 10 deletions
diff --git a/extras/multipath/README b/extras/multipath/README index 6a5637de4b..951c2788bc 100644 --- a/extras/multipath/README +++ b/extras/multipath/README @@ -3,6 +3,7 @@ Dependancies : o libdevmapper : comes with device-mapper-XXXX.tar.gz See www.sistina.com + This lib has been dropped in the multipath tree o libsysfs : comes with sysutils See ftp.kernel.org/pub/linux/utils/kernel/hotplug/ @@ -34,8 +35,9 @@ In 2.5+, we rely on libsysfs (sysutils) to access to sysfs device enums. the wwid is retrieved by a switch fonction. Only White -Listed HW can filled this field. For now only -StorageWorks HW is White Listed. (See notes) +Listed HW can filled this field. For now every FC array +HW listed in kernel's devinfo.c is White Listed, assuming +the WWID is stored is the SCSI-3 standard 0x83 EVPD page. When all_paths is filled, we coalesce the paths and store the result in mp array. Each mp is a struct like this : @@ -47,25 +49,21 @@ struct multipath { }; When mp is filled, the device maps are fed to the kernel -through libdevmapper. Stale paths (failed TUR) are -discarded. +through libdevmapper. Notes : ======= -o make sure you have enough /dev/sg* nodes - (/dev/MAKEDEV if necesary) +o On 2.4, make sure you have enough /dev/sg* nodes + (/dev/MAKEDEV if necesary). Same goes for /dev/sd* o path coalescing relies on a path unique id being found. This unique id, lacking a standard method, is vendor specific. A switch function (get_unique_id) is present and an example function is provided for storageworks - arrays (get_storageworks_wwid). Feel free to enrich + arrays (get_evpd_wwid). Feel free to enrich with hardware you have at hand :) -o Something goes wrong with sd.o, qla2200 & dm-mod - refcounting : I can't unload these modules after exec. - o The kernel does NOT manage properly ghosts paths with StorageWorks HW. Seems nobody cares after a load of posts to linux-scsi. |