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Old 10-01-2013, 06:32 AM   #1
harwansh
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Registered: Dec 2006
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Question RDAC to multipath conversion in SuSe Linux


Hi,

I have SuSe linux 10 SP3 in running on IBM Power server with RDAC driver of IBM Storage.
Now customer is migrating storage from IBM DS 5K to V7000. V7K support multipath opposite to RDAC.

I need to migrate from RDAC to Multipath. Is there any procedure to migrate.

Any suggestion are welcome.

Thanks
 
Old 10-01-2013, 09:17 AM   #2
MensaWater
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Haven't done IBM to Multipath but we did do EMC PowerPath to Multipath when we converted to a Hitachi VSP disk array.

Below I've pasted in the steps written at the time we did that 2-3 years ago. The powermt command mentioned is specifically for EMC.

Important point below is to remove the existing tool (RDAC) and driver if any BEFORE turning on native Linux multipathing.

Hopefully it will give you some ideas as to the general things you should be looking at - you'll of course have to adapt it for what you're doing as it can NOT be used as is for what you're doing:

Linux VSP Setups

Multipathing

1. Run powermt display dev=all /root/powermt.YYYYMMDD. This is to have information for RAW devices as well as previous mappings for reference.
2. From the output file, /root/powermt.YYYYMMDD, you just created, locate a single multi-pathed device from the DMX and note the I/O paths, these are needed at a later step. In the below example these are /dev/sdct and /dev/sdko

Pseudo name=emcpowercq
Symmetrix ID=000190100402
Logical device ID=0E27
state=alive; policy=SymmOpt; priority=0; queued-IOs=0
==============================================================================
---------------- Host --------------- - Stor - -- I/O Path - -- Stats ---
### HW Path I/O Paths Interf. Mode State Q-IOs Errors
==============================================================================
0 qla2xxx sdct FA 9dA active alive 0 0
1 qla2xxx sdko FA 8dA active alive 0 0

3. Make sure Power Path has been uninstalled before trying to do the multipath setup. The server will crash and go into continuous reboots if Power Path and dm-multipath modules both try to manage the disks.
4. Double check that all of the disks needed for the migration have been readied to be assigned to host group for this host.
5. Zone in the host to the VSP.
6. Next cd /sys/class/scsi_host.
7. Run cat host*/proc_name and look for FC adapters, which are usually of the form qla2xxx but not always.
8. Run echo “- - -“ > hostX/scan to force the card to rescan the devices presented with hostX being the instance number of the hosts listed that were FC cards.
9. Make sure the VSP is seeing the host now.
10. Have the LUNs being migrated mapped into the host group.
11. Ensure the device-mapper-multipath software is installed using yum list device-mapper-multipath. If not installed run :
a. yum -y install device-mapper-multipath to install it.
b. modprobe dm-multipath
c. service multipathd start
d. multipath -l -v2
e. chkconfig multipathd on

12. Do cp -p /etc/multipath.conf /etc/multipath.conf.YYYYMMDD
13. Run the script to find the names of the disk vendors to be blacklisted in the multipath file to keep them from being seen or scanned by the multipath daemon. Look for the Perc Controller, Megaraid and CD/DVDROM devices.
14. for each in `cd /sys/block ; ls -d sd*`; do A=`scsi_id -g -u -s /block/$each`; B=` scsi_id -g -a -p0x80 -x -s /block/$each | awk '/VENDOR/ {printf "%s ",$0}; /MODEL/ {print $0}'`; echo $each $A $B; done
15. Under the blacklist section in the multipath.conf do the following.
a. Comment out the line ‘devnode “*”’ as this says to blacklist everything from the multipath daemons.
b. Between the brockets for the blacklist section add device node entries for the Perc Controller(s) and CD/DVDRom. Wildcards are permitted. * Sometimes the CD/DVD-Rom are excluded due to previous udev rules for Symmetrix.
See examples below:
blacklist {
# devnode “*”
device {
vendor “DELL”
product “PERC*”
}
device {
vendor “TSSTcorp”
product “*”
}
} #blacklist section

16. Find the uncommented defaults section and make sure that it has user_friendly_names yes defined. This has the software create a /dev/mapper/mpathX device as well as a World Wide ID (WWID) device name. This is to give a much better name for configuration than the long WWID name. It should look like the following:
## Use user friendly names, instead of using WWIDs as names.
defaults {
user_friendly_names yes
}

17. Go to the bottom of the file and add a device section for the Hitachi matching one below. These are the recommended settings for a USP and this also suggested for a VSP.
devices {
device {
vendor "HITACHI"
product "OPEN-V.*"
getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
features "0"
hardware_handler "0"
path_grouping_policy multibus
failback immediate
rr_weight uniform
rr_min_io 1000
path_checker tur
}
}
 
Old 10-02-2013, 12:33 AM   #3
harwansh
LQ Newbie
 
Registered: Dec 2006
Posts: 4

Original Poster
Rep: Reputation: 0
Quote:
Originally Posted by MensaWater View Post
Haven't done IBM to Multipath but we did do EMC PowerPath to Multipath when we converted to a Hitachi VSP disk array.

Below I've pasted in the steps written at the time we did that 2-3 years ago. The powermt command mentioned is specifically for EMC.

Important point below is to remove the existing tool (RDAC) and driver if any BEFORE turning on native Linux multipathing.

Hopefully it will give you some ideas as to the general things you should be looking at - you'll of course have to adapt it for what you're doing as it can NOT be used as is for what you're doing:

Linux VSP Setups

Multipathing

1. Run powermt display dev=all /root/powermt.YYYYMMDD. This is to have information for RAW devices as well as previous mappings for reference.
2. From the output file, /root/powermt.YYYYMMDD, you just created, locate a single multi-pathed device from the DMX and note the I/O paths, these are needed at a later step. In the below example these are /dev/sdct and /dev/sdko

Pseudo name=emcpowercq
Symmetrix ID=000190100402
Logical device ID=0E27
state=alive; policy=SymmOpt; priority=0; queued-IOs=0
==============================================================================
---------------- Host --------------- - Stor - -- I/O Path - -- Stats ---
### HW Path I/O Paths Interf. Mode State Q-IOs Errors
==============================================================================
0 qla2xxx sdct FA 9dA active alive 0 0
1 qla2xxx sdko FA 8dA active alive 0 0

3. Make sure Power Path has been uninstalled before trying to do the multipath setup. The server will crash and go into continuous reboots if Power Path and dm-multipath modules both try to manage the disks.
4. Double check that all of the disks needed for the migration have been readied to be assigned to host group for this host.
5. Zone in the host to the VSP.
6. Next cd /sys/class/scsi_host.
7. Run cat host*/proc_name and look for FC adapters, which are usually of the form qla2xxx but not always.
8. Run echo “- - -“ > hostX/scan to force the card to rescan the devices presented with hostX being the instance number of the hosts listed that were FC cards.
9. Make sure the VSP is seeing the host now.
10. Have the LUNs being migrated mapped into the host group.
11. Ensure the device-mapper-multipath software is installed using yum list device-mapper-multipath. If not installed run :
a. yum -y install device-mapper-multipath to install it.
b. modprobe dm-multipath
c. service multipathd start
d. multipath -l -v2
e. chkconfig multipathd on

12. Do cp -p /etc/multipath.conf /etc/multipath.conf.YYYYMMDD
13. Run the script to find the names of the disk vendors to be blacklisted in the multipath file to keep them from being seen or scanned by the multipath daemon. Look for the Perc Controller, Megaraid and CD/DVDROM devices.
14. for each in `cd /sys/block ; ls -d sd*`; do A=`scsi_id -g -u -s /block/$each`; B=` scsi_id -g -a -p0x80 -x -s /block/$each | awk '/VENDOR/ {printf "%s ",$0}; /MODEL/ {print $0}'`; echo $each $A $B; done
15. Under the blacklist section in the multipath.conf do the following.
a. Comment out the line ‘devnode “*”’ as this says to blacklist everything from the multipath daemons.
b. Between the brockets for the blacklist section add device node entries for the Perc Controller(s) and CD/DVDRom. Wildcards are permitted. * Sometimes the CD/DVD-Rom are excluded due to previous udev rules for Symmetrix.
See examples below:
blacklist {
# devnode “*”
device {
vendor “DELL”
product “PERC*”
}
device {
vendor “TSSTcorp”
product “*”
}
} #blacklist section

16. Find the uncommented defaults section and make sure that it has user_friendly_names yes defined. This has the software create a /dev/mapper/mpathX device as well as a World Wide ID (WWID) device name. This is to give a much better name for configuration than the long WWID name. It should look like the following:
## Use user friendly names, instead of using WWIDs as names.
defaults {
user_friendly_names yes
}

17. Go to the bottom of the file and add a device section for the Hitachi matching one below. These are the recommended settings for a USP and this also suggested for a VSP.
devices {
device {
vendor "HITACHI"
product "OPEN-V.*"
getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
features "0"
hardware_handler "0"
path_grouping_policy multibus
failback immediate
rr_weight uniform
rr_min_io 1000
path_checker tur
}
}

Thanks for your reply.

I am more concern with data. Will we able to get the data or have restore. File systems are configured with LVM. After enabling the multipath i will get the /dev/mapper/mpath* rather than /dev/sd*. Will we able to mount the filesystem?
 
Old 10-02-2013, 03:21 PM   #4
MensaWater
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Location: Atlanta Georgia USA
Distribution: Redhat (RHEL), CentOS, Fedora, CoreOS, Debian, FreeBSD, HP-UX, Solaris, SCO
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First:
***ALWAYS MAKE BACKUPS BEFORE PEFORMING ANY MAJOR CHANGES***

Having said that:
LVM is a different layer of things. It can be put on meta disks, multipath disks or regular disks (anything it marks as a PV (Pysical Volume). At start up LVM scans the devices to see if any of them are PVs and should activate VGs (Volume Groups) so long as it finds all the PVs it needs for a given VG.

For the most part we are doing LVM here as well and have all our SAN stuff in LVM.

So the answer is it *SHOULD* preserve your data and mount it with whatever your PVs do.

As noted I haven't done the IBM/RDAC stuff so my *ASSUMPTION* is that is not writing anything to the disks as seen by the OS so they'd be seen the same.

You haven't said HOW you're implementing the new storage though. In our case we were able virtualize the EMC disks THROUGH the Hitachi's virtualization. In your case if you're moving from one storage platform to another does it allow you to virtualize? If not can you convert the current IBM/RDAC into Linux native multipathing?

If the latter then what you could do is do that first then present your new storage and add the new PVs to existing VGs and use the pvmove command to move the data off the existing IBM PVs to the new storage PVs inside the VG. (That can be done with everything still online.)

Another alternative would be simply to create new VGs and LVs (Logical Volumes) using PVs from the new storage while the old IBM based PVs and VGs are still online then use the cp command to copy from filesystems of the old LVs to the filesystems of the new LVs. For that alternative you probably do want to have the specific filesystems quiesced while doing the copy to insure nothing is change.

P.S. You can even set specific naming in your multipath.conf if you can determine a pattern returned by scsi_id for your devices. This lets you get rid of the random mpath## names that can change on each reboot in favor of static names that are the same each time you reboot. But as noted above this is NOT necessary as LVM will find the new mpath## names on a reboot because it scans the disks to determine what PV it is rather than being tied to a specific name. (i.e. in one boot you mmight have vgbubba with PVs /dev/mpath/mpath12 and /dev/mpath/mpath20 that n next boot would instead be /dev/mpath/mpath7 and /dev/mpath/mpath31)
 
Old 10-03-2013, 02:56 AM   #5
harwansh
LQ Newbie
 
Registered: Dec 2006
Posts: 4

Original Poster
Rep: Reputation: 0
Hi
Thanks for your information. I also feel the same. Data should be available after virtualizing the DS 5K to V7K. DS5K will be virtulize through V7000. DS 5K will be managed by V7000.

Before doing the activities i will simulate in the same storage for conversion. And will ensure backups are available if required.

Thanks for your help.
 
  


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