[Bug 204646] 10.2 iSCSI backed zpool shows imporper warnings about non-native block sizes that 10.1 doesn't show

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=204646

            Bug ID: 204646
           Summary: 10.2 iSCSI backed zpool shows imporper warnings about
                    non-native block sizes that 10.1 doesn't show
           Product: Base System
           Version: 10.2-RELEASE
          Hardware: amd64
                OS: Any
            Status: New
          Severity: Affects Many People
          Priority: ---
         Component: misc
          Assignee: freebsd-bugs at FreeBSD.org
          Reporter: chris at acsi.ca

This is similar to Bug 197513, but that is a 9.3 system.

Consider this scenario:

Virtual FreeBSD Machine Initiator, with a zpool created out of iSCSI disks.
Physical FreeBSD Machine Target, with a zpool holding a sparse file that is the
target for the iSCSI disk. 

- The 10.2 Machines are 10.2-p7 RELEASE, updated via freebsd-update, no custom.
- The 10.1 Machine are 10.1-p24 RELEASE, updated via freebsd-update, no custom.
- iSCSI is all CAM iSCSI, not the old istgt platform. 
- The iSCSI Target is a sparse file, stored on a zpool (not a vdev Target)

The target machine is the same physical machine, with the same zpools - I
either boot 10.1 or 10.2 for testing, and use the same zpool/disks 

to ensure nothing is changing. 

If I have a 10.2 iSCSI Initiator (client) connected to a 10.2 iSCSI Target, I
get eroneous warnings. 
If I have a 10.1 iSCSI Initiator (client) connected to a 10.1 iSCSI Target, I
don't get the warnings. 

On the iSCSI Target, the file that backs the iSCSI disk is stored in a zpool
that has a recordsize=64k set. 

It's something in the CAM iSCSI Target code that is reporting the zfs
recordsize as the sector size. 

If you use a 10.1 iSCSI Initiator connected to a 10.2 iSCSI Target, or 10.1
iSCSI Target, this is what you see on the Initiator:


#zpool status
  pool: iscsi-nfs
 state: ONLINE
  scan: scrub repaired 0 in 0h0m with 0 errors on Tue Nov 17 15:25:51 2015
config:

        NAME                              STATE     READ WRITE CKSUM
        iscsi-nfs                         ONLINE       0     0     0
          diskid/DISK-MYSERIAL%20%20%201  ONLINE       0     0     0

errors: No known data errors

  pool: iscsi-nfs1
 state: ONLINE
  scan: scrub repaired 0 in 0h0m with 0 errors on Tue Nov 17 15:25:51 2015
config:

        NAME                              STATE     READ WRITE CKSUM
        iscsi-nfs1                        ONLINE       0     0     0
          diskid/DISK-MYSERIAL%20%20%200  ONLINE       0     0     0

errors: No known data errors

With a 10.2 iSCSI Initiator connected to a 10.2 iSCSI Target, this is what I
see on zpool status:

# zpool status
  pool: iscsi-nfs
 state: ONLINE
status: One or more devices are configured to use a non-native block size.
        Expect reduced performance.
action: Replace affected devices with devices that support the
        configured block size, or migrate data to a properly configured
        pool.
  scan: scrub repaired 0 in 0h0m with 0 errors on Tue Nov 17 15:25:51 2015
config:

        NAME                              STATE     READ WRITE CKSUM
        iscsi-nfs                         ONLINE       0     0     0
          diskid/DISK-MYSERIAL%20%20%200  ONLINE       0     0     0  block
size: 4096B configured, 65536B native

errors: No known data errors

  pool: iscsi-nfs1
 state: ONLINE
status: One or more devices are configured to use a non-native block size.
        Expect reduced performance.
action: Replace affected devices with devices that support the
        configured block size, or migrate data to a properly configured
        pool.
  scan: scrub repaired 0 in 0h0m with 0 errors on Tue Nov 17 15:25:51 2015
config:

        NAME                              STATE     READ WRITE CKSUM
        iscsi-nfs1                        ONLINE       0     0     0
          diskid/DISK-MYSERIAL%20%20%201  ONLINE       0     0     0  block
size: 4096B configured, 65536B native

errors: No known data errors


Notice the block size warnings. 


The /etc/ctl.conf on both of the target machines is:


portal-group pg0 {
        discovery-auth-group no-authentication
        listen 0.0.0.0
        listen [::]
}

        lun 0 {
                path /pool92/iscsi/iscsi.zvol
                blocksize 4K
                size 5T
                option unmap "on"
                option scsiname "pool92"
                option vendor "pool92"
                option insecure_tpc "on"
        }
}


target iqn.iscsi1.zvol {
        auth-group no-authentication
        portal-group pg0

        lun 0 {
                path /pool92_1/iscsi/iscsi.zvol
                blocksize 4K
                size 5T
                option unmap "on"
                option scsiname "pool92_1"
                option vendor "pool92_1"
                option insecure_tpc "on"
        }
}


Note the 4k size for my iSCSI Blocks. 


I believe this error message to be incorrect, as recordsize=64k on the Target
will not affect the ashift value at all, which is what this warning is really
designed for, correct? It's going to warn when you have ashift=9 on a 4k drive,
or similar mis-matches. 

The last interesting bit is that somehow the iSCSI Initiator is believing that
the Target's sector size _is_ the zfs recordsize, as a zpool creation with a
iSCSI drive in this situation trys zet the zpool's ashift to
vfs.zfs.max_auto_ashift of 13 (8k Sectors)


Thanks.

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