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-rw-r--r--extras/multipath/README18
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.