Hi Joost,
On 6/4/24 12:29 AM, Joost Roeleveld wrote:
I don't use FibreChannel myself (can't justify the cost).
I hear that. I manage an old EMC for a friend who's still using it as
clustered storage for an old VMware install. It started giving us
occasional hiccups (corrected memory errors) so we're assembling a cold
spare. He's footing the bill and I get to play with the equipment.
}:-) Though honestly, the bill ins't that bad any more.
But with SAS drives with dual expanders and 2 HBAs, I do get multipath
to work.
ACK
The OS sees every drive 4 times (2 HBAs, each 2 paths to every drive).
Four times surprises me. -- I know that SAS drives have two SAS
channels / lanes / terms? on them. But I don't know how those are both
connected to two controllers. I would have naively assumed each drive
showed up as two drives, one for each channel / lane / ???. I guess if
there is some sort of multiplexor / breakout / backplane there's a way
to connect both controllers to both channels / lanes / ??? on each drive
and four paths would make sense.
Aside: I'd like to know more about how you're doing that physical
connection.
On top of this, I run multipath with the default configuration and use
the corresponding /dev/mapper/... entries.
So dev-mapper multipathing is working in a contemporary Gentoo system.
Thank you for the confirmation. That's what I was wanting.
I'm going to assume that I have something mis-configured in dev-mapper
as it wasn't originally used on my test system and only added for the FC
testing.
I NEVER use the any of the other entries in the /dev/... tree.
I understand what you're saying. I'd be following suit if multi-path
was working. -- I'm /well/ aware of the hazards of using the member /
backing disks vs the multi-path disk.
Based on that, do you see the fibrechannel drives show up as /dev/sd...
entries on your system at all?
Yes, both test LUNs (1 x 10 GB and 1 x 100 GB) show up once per client
HBA port.
Aside: I don't have the fiber switch in place yet, so I'm using cables
directly out of an HBA port into an EMC controller port.
I am seeing the expected number of /dev/sd* for the LUNs.
/dev/sdd = 10 GB
/dev/sdf = 100 GB
/dev/sdg = 10 GB
/dev/sdh = 100 GB
If yes, then multipath should pick them up.
That's what I thought.
As I get into the multipath command and debug things it seems like
something thinks the paths are offline despite the underlying member /
backing disks being online and accessible.
If not, I would expect you need to get them seen via all the paths first.
Yep. I can see them via their underlying member / backing paths without
any problem.
This feels like a device-mapper -> multipath issue to me.
It /may/ be complicated by the old EMC but I'd be surprised by that.
Thank you for confirming that device-mapper multipathing should be
working. -- Now that I know that I'm not chasing a ghost, I'll spend
some more time making sure that device-mapepr and multipathing is
installed and configured properly (USE flags, kernel options, user space
utilties, etc) before taking another swing at dm-multipath for the SAN LUNs.
--
Grant. . . .
