[OpenIndiana-discuss] mpt_sas target to device mapping

[Liam Slusser]

Hi All -

We have a rather large zfs array of 276 disks plus 2 log devices (in a
mirror) and 2 ssd cache devices.  The total volume is 798T.  The server is
a 2u Dell r720xd with 5 LSI 9207-8e SAS controllers and 23 Dell MD1200
12-disks arrays.  All the disks are SAS.  We're running OpenIndiana.

The system works wonderfully for what we use it for (basically a big nfs
server) with very little issues.  However, with so many disks, disk
failures obviously happen.  Generally when we lose a disk ZFS marks the
disk offline and I can use prtconf and the LSI tool sas2ircu to map the
device back to a physical location in one of the MD1200s.

However, every once In a while a disk fails in such a way it hangs the
zpool.  Modifying the io timeout values helped greatly for OI to drop a
disk when it fails but still sometimes a disk has issues that hang the
system.

When this happens any command that tries to access the disk hangs.  So you
can't use system tools like zpool or format.  You also can't modify the
device state with cfgadm, so a cfgadm -c unconfigure command just hangs.
Sometimes if you wait long enough through enough retires your command will
finally succeed, but generally, it just takes too long.  The event log
shows error messages like this over and over:

May  2 23:02:18 zintstore01 scsi: [ID 107833 kern.warning] WARNING: /pci at ff
,0/pci8086,3c0a at 3,2/pci1000,3080 at 0 (mpt_sas7):
May  2 23:02:18 zintstore01     Disconnected command timeout for Target 70
May  2 23:02:18 zintstore01 scsi: [ID 365881 kern.info] /pci at ff
,0/pci8086,3c0a at 3,2/pci1000,3080 at 0 (mpt_sas7):
May  2 23:02:18 zintstore01     Log info 0x31140000 received for target 70.
May  2 23:02:18 zintstore01     scsi_status=0x0, ioc_status=0x8048,
scsi_state=0xc

Mapping "target 70" back to a physical disk is a massive pain, they don't
make it easy and I haven't found a command/utility to do this for me.  Here
is my procedure:

1)  I pull the mptsas mapping out of the kernel:

# echo "::mptsas -t" | mdb -k > /tmp/mdbk-output

2) I found that the event log prints the target in decimal, but the
mdb kernel output is in hex.  So convert the target ID into hex

# printf "%x\n" 70
46

3)  Search through your output looking for that dev id to get the sasaddress

# egrep "ON=|devhdl 46" /tmp/mdbk-output
ffffff1156096000    0     0       0 ON=D0
                 devhdl 46, sasaddress 5000039608caef8a, phymask f0,devinfo
401
ffffff11569b9000    6     0       0 ON=D0
                 devhdl 46, sasaddress 50000c0f01c7310a, phymask f0,devinfo
401
ffffff1177028000    7     0       0 ON=D0
                 devhdl 46, sasaddress 5000c500579d2885, phymask f0,devinfo
401

4)  Now I have 5 controllers, so three of them have a deviceID of 46.  To
figure out which one get a list of controllers and their path

# echo "::mptsas -d" | mdb -k
ffffff1157c00000    6     0       0 ON=D0

                 Path in device tree /pci at ff,0/pci8086,3c02 at 1/pci1000,3040 at 0

        mptsas_t inst ncmds suspend  power
================================================================================
ffffff1177fab000    7     0       0 ON=D0

                 Path in device tree /pci at ff,0/pci8086,3c0a at 3
,2/pci1000,3080 at 0
...

Map the device path in the original event log "/pci at ff,0/pci8086,3c0a at 3
,2/pci1000,3080 at 0" to the mptsas_t address of ffffff1177fab000.  Now look
back at step three and match the mptsas target ffffff1177fab000 and grab
the sasaddress of the drive 5000c500579d2885.

5)  Once you have the sasaddress 5000c500579d2885 you can use prtconf -v
and search for it, then scroll down a few lines to get the device path
/dev/dsk/c1t5000C500579D2887d0.  Boom!  Now you can issue a "zpool remove
pool c1t5000C500579D2887d0".

Unfortunately, the only way I've figured out how to get the slot/enclosure
information is with the sas2ircu tool but it does not include the
sasaddress, only the enclosure/slot and serial number.  So I grab the
device serial number with prtconf then look for it in the sas2ircu output.
I've found it helpful to keep a copy of the current disk layout using
sas2ircu so I can map a drive to a slot in case the system is hung in such
a way I can't use the command.  Then I can call a data center tech to have
them pull slot N in device Y.  Once the device is pulled the system
immediately marks the disk bad and everything returns to normal.

Is there any easier way to do this?  I suppose I could script this and make
a handy tool but I'm wondering if anybody has a better way.

thanks!
liam