On 10/19/20 1:03 PM, Muneendra Kumar M wrote:
Hi Michael,
Regarding the TUR (Test Unit Ready)command which I was mentioning .
Multipath daemon issues TUR commands on a regular intervals to check the
path status.
When a port_state is set to marginal we are not suppose to end up failing
the cmd with DID_TRANSPORT_MARGINAL with out proceeding it.
This may leads to give wrong health status.
If your daemon works such that you only move paths from marginal to
active if you get an ELS indicating the path is ok or you get a link up,
then why have multipathd send path tester IO to the paths in the
marginal path group? They do not do anything do they?
Hannes/James Correct me if this is wrong.
Regards,
Muneendra.
-----Original Message-----
From: Muneendra Kumar M [mailto:muneendra.kumar@xxxxxxxxxxxx]
Sent: Monday, October 19, 2020 11:01 PM
To: 'Hannes Reinecke' <hare@xxxxxxx>; 'Michael Christie'
<michael.christie@xxxxxxxxxx>
Cc: 'linux-scsi@xxxxxxxxxxxxxxx' <linux-scsi@xxxxxxxxxxxxxxx>;
'jsmart2021@xxxxxxxxx' <jsmart2021@xxxxxxxxx>; 'emilne@xxxxxxxxxx'
<emilne@xxxxxxxxxx>; 'mkumar@xxxxxxxxxx' <mkumar@xxxxxxxxxx>
Subject: RE: [PATCH v3 05/17] scsi_transport_fc: Added a new rport state
FC_PORTSTATE_MARGINAL
Hi Michael,
Oh yeah, to be clear I meant why try to send it on the marginal path
when you are setting up the path groups so they are not used and only the
optimal paths are used.
When the driver/scsi layer fails the IO then the multipath layer will
make sure it goes on a optimal path right so you do not have to worry
about hitting a cmd timeout and firing off the scsi eh.
However, one other question I had though, is are you setting up
multipathd so the marginal paths are used if the optimal ones were to
fail (like the optimal paths hit a link down, dev_loss_tmo or
fast_io_fail fires, etc) or will they be treated like failed paths?
So could you end up with 3 groups:
1. Active optimal paths
2. Marginal
3. failed
If the paths in 1 move to 3, then does multipathd handle it like a all
paths down or does multipathd switch to #2?
Actually, marginal path work similar to the ALUA non-optimized state.
Yes, the system can sent I/O to it, but it'd be preferable for the I/O to
be moved somewhere else.
If there is no other path (or no better path), yeah, tough.
Hence the answer would be 2)
[Muneendra]As Hannes mentioned if there are no active paths, the marginal
paths will be moved to normal and the system will send the io.
Regards,
Muneendra.
