Chris's AIX Blog

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In a perfect world....rootvg would always reside on hdisk0.

cggibbo Tags: hdisk0 chris_gibson rendev rootvg aix 9 Comments 26,493 Views

In a perfect world, 99.9% of AIX administrators would prefer their systems to look like this:

# lspv | grep rootvg

hdisk0 00c342c68dfcbdfb rootvg active

However, in reality, 99.9% of AIX administrators live with systems that look something like this:

# lspv | grep rootvg

hdisk39 00c342c68dfcbdfb rootvg active

And 99.9% of them don’t have time to tidy up their systems so that rootvg resides on hdisk0.

Most of them have much bigger fish to fry, such as performance, virtualisation, automation, security, project delivery, TPS reports, etc!

If they did have time, they could use the mirrorvg and rendev commands to ‘bring order to the Universe’.

1. Add a new disk to the system.

# lspv

hdisk39 00c342c68dfcbdfb rootvg active

hdisk40 00c342c6161c6b47 None

2. Rename the new disk to hdisk0.

# rendev -l hdisk40 -n hdisk0

hdisk0

3. Add the disk to rootvg and mirror to it.

# extendvg rootvg hdisk0

# mirrorvg rootvg hdisk0

0516-1804 chvg: The quorum change takes effect immediately.

0516-1126 mirrorvg: rootvg successfully mirrored, user should perform

bosboot of system to initialize boot records. Then, user must modify

bootlist to include: hdisk0 hdisk39.

4. Create a boot image on hdisk0.

# bosboot –a –d /dev/hdisk0

bosboot: Boot image is 49180 512 byte blocks.

# ipl_varyon -i

[S 3670248 14942228 07/24/12-10:18:11:104 ipl_varyon.c 1270] ipl_varyon -i

PVNAME BOOT DEVICE PVID VOLUME GROUP ID

hdisk39 YES 00c342c68dfcbdfb0000000000000000 00c342c600004c00

hdisk0 YES 00c342c6161c6b470000000000000000 00c342c600004c00

[E 3670248 0:087 ipl_varyon.c 1410] ipl_varyon: exited with rc=0

5. Check and update the bootlist. Ensure hdisk0 is in the bootlist.

# bootlist –m normal hdisk0

# bootlist –m normal –o

hdisk0 blv=hd5 pathid=0

hdisk0 blv=hd5 pathid=1

6. Unmirror rootvg on hdisk39. Remove hdisk39 from rootvg.

# unmirrorvg rootvg hdisk39

0516-1246 rmlvcopy: If hd5 is the boot logical volume, please run 'chpv -c <diskname>'

as root user to clear the boot record and avoid a potential boot

off an old boot image that may reside on the disk from which this

logical volume is moved/removed.

0516-1804 chvg: The quorum change takes effect immediately.

0516-1144 unmirrorvg: rootvg successfully unmirrored, user should perform

bosboot of system to reinitialize boot records. Then, user must modify

bootlist to just include: hdisk0.

# lspv –l hdisk39

# reducevg rootvg hdisk39

7. Order in the Universe has been restored.

# lspv | grep rootvg

hdisk0 00c342c6161c6b47 rootvg active

Of course, all of this assumes that the name, hdisk0, is not already in use by a hdisk in another volume group on the system.

Again, if you have the time, then you could perform the following to rectify the situation.

1. datavg resides on hdisk0.

# lspv | grep datavg

hdisk0 00c342c6161c6b47 datavg active

2. Unmount all data file systems in this volume group. Varyoff the VG.

# unmount /datafs

# varyoffvg datavg

3. Rename hdisk0 to hdisk99 (or something other than hdisk0).

# rendev -l hdisk0 -n hdisk99

hdisk99

4. Varyon the volume group, datavg. Mount the data file systems in datavg.

# varyonvg datavg

# mount /datafs

5. datavg now resides on (the newly renamed) hdisk99.

# lspv | grep datavg

hdisk99 00c342c6161c6b47 datavg

Now that the name, hdisk0, is free, you can perform the steps, outlined above, to restore ‘Order in the Universe’ and put rootvg back on hdisk0!

Renaming devices in AIX 7.1

cggibbo Tags: 7.1 gibson aix chris rendev 20 Comments 59,414 Views

I remember reading this interesting document about some challenges renaming AIX devices.

http://gibsonnet.net/aix/ibm/The_Fun_of_Oracle_RAC_ASM_and_Device_Names.doc

This poor guy had to jump through some hoops to rename some disk and network devices in a clustered AIX (Oracle RAC) environment.

This comment stayed with me:

“The easy way to get network adapters and disk names to match between systems would be to run something like

# chdev –l old_name –n new_name

Except, this command option does NOT exist.”

Since then I’ve always been on the “look out” for an easy way to rename devices in AIX.

In particular in large clustered environments where it is sometimes very important to have the same disk and network device names in sync across all nodes in a cluster. And besides, it’s a lot easier to verify a cluster configuration if the hdisk names are all the same. Matching PVIDs works but it requires a lot more effort! For example, knowing that hdisk123 is the same device on all nodes makes life easier than scanning lspv output for a PVID like 00f6048868b4gead. Of course you can script things to make this easier but it would be great if you didn’t need to do this and that there was a way to rename devices as needed, without resorting to unsupported methods.

Well, this is no longer an issue for AIX.

Starting with AIX 7.1, you can now easily rename devices. A new command called rendev was introduced to allow AIX administrators to rename devices as required.

From the man page:

The rendev command enables devices to be renamed. The device to be renamed, is specified with the -l flag, and the new desired name is specified with the -n flag.

The new desired name must not exceed 15 characters in length. If the name has already been used or is present in the /dev directory, the operation fails. If the name formed by appending the new name after the character r is already used as a device name, or appears in the /dev directory, the operation fails.

If the device is in the Available state, the rendev command must unconfigure the device before renaming it. This is similar to the operation performed by the rmdev -l Name command. If the unconfigure operation fails, the renaming will also fail. If the unconfigure succeeds, the rendev command will configure the device, after renaming it, to restore it to the Available state. The -u flag may be used to prevent the device from being configured again after it is renamed.

Some devices may have special requirements on their names in order for other devices or applications to use them. Using the rendev command to rename such a device may result in the device being unusable. Note: To protect the configuration database, the rendev command cannot be interrupted once it has started. Trying to stop this command before completion, could result in a corrupted database.

This functionality was required to help simplify cluster device configuration with the new Cluster Aware AIX (CAA) feature in AIX 7.1.

I’ll be blogging about CAA in a future post.

Here are some examples of using the rendev command on AIX 7.1 (GA) system. In the first example I will rename hdisk3 to hdisk300. Note: hdisk3 is not in use (busy).

If the disk had been allocated to a volume group, I would have needed to varyoff the volume group first.

# lspv

hdisk0 00f61ab2f73e46e2 rootvg active

hdisk1 00f61ab20bf28ac6 None

hdisk2 00f61ab2202f7c0b None

hdisk4 00f61ab20b97190d None

hdisk3 00f61ab2202f93ab None

# rendev -l hdisk3 -n hdisk300

# lspv

hdisk0 00f61ab2f73e46e2 rootvg active

hdisk1 00f61ab20bf28ac6 None

hdisk2 00f61ab2202f7c0b None

hdisk4 00f61ab20b97190d None

hdisk300 00f61ab2202f93ab None

Easy!

Next, I’ll rename a virtual SCSI adapter. I renamed vscsi0 to vscsi2. Note: I placed the adapter, vscsi0, in a Defined state before renaming the device.

# rmdev -Rl vscsi0

# lsdev -Cc adapter

ent0 Available Virtual I/O Ethernet Adapter (l-lan)

ent1 Available Virtual I/O Ethernet Adapter (l-lan)

vsa0 Available LPAR Virtual Serial Adapter

vscsi0 Defined Virtual SCSI Client Adapter

vscsi1 Available Virtual SCSI Client Adapter

# rendev -l vscsi0 -n vscsi2

# lsdev -Cc adapter

ent0 Available Virtual I/O Ethernet Adapter (l-lan)

ent1 Available Virtual I/O Ethernet Adapter (l-lan)

vsa0 Available LPAR Virtual Serial Adapter

vscsi1 Available Virtual SCSI Client Adapter

vscsi2 Defined Virtual SCSI Client Adapter

Now I’ll rename a network adapter from ent0 to ent10. I bring down the interface before changing the device name

# lsdev -Cc adapter

ent0 Available Virtual I/O Ethernet Adapter (l-lan)

ent1 Available Virtual I/O Ethernet Adapter (l-lan)

vsa0 Available LPAR Virtual Serial Adapter

vscsi1 Available Virtual SCSI Client Adapter

vscsi2 Defined Virtual SCSI Client Adapter

# ifconfig en0

en0: flags=1e080863,480<UP,BROADCAST,NOTRAILERS,RUNNING,SIMPLEX,MULTICAST,GROUPRT,64BIT,CHECKSUM_OFFLOAD(ACTIVE),CHAIN>

inet 10.1.20.19 netmask 0xffff0000 broadcast 10.153.255.255

tcp_sendspace 262144 tcp_recvspace 262144 rfc1323 1

# ifconfig en0 down detach

# rendev -l ent0 -n ent10

# lsdev -Cc adapter

ent1 Available Virtual I/O Ethernet Adapter (l-lan)

ent10 Available Virtual I/O Ethernet Adapter (l-lan)

vsa0 Available LPAR Virtual Serial Adapter

vscsi1 Available Virtual SCSI Client Adapter

vscsi2 Defined Virtual SCSI Client Adapter

# rendev -l en0 -n en10

# chdev -l en10 -a state=up

en10 changed

# mkdev -l inet0

inet0 Available

# ifconfig en10

en10: flags=1e080863,480<UP,BROADCAST,NOTRAILERS,RUNNING,SIMPLEX,MULTICAST,GROUPRT,64BIT,CHECKSUM_OFFLOAD(ACTIVE),CHAIN>

inet 10.1.20.19 netmask 0xffff0000 broadcast 10.153.255.255

tcp_sendspace 262144 tcp_recvspace 262144 rfc1323 1

If you want to be creative you can rename devices to anything you like (as long as it’s not more than 15 characters). For example I’ll rename vscsi2 to myvscsiadapter.

# rendev -l vscsi2 -n myvscsiadapter

# lsdev -Cc adapter

ent1 Available Virtual I/O Ethernet Adapter (l-lan)

myadapter Available Virtual I/O Ethernet Adapter (l-lan)

myvscsiadapter Defined Virtual SCSI Client Adapter

vsa0 Available LPAR Virtual Serial Adapter

vscsi1 Available Virtual SCSI Client Adapter

And in the last example I’ll demonstrate changing virtual SCSI adapter device names on a live system.

This is single disk system (hdisk0), with two vscsi adapters.

# lspv

hdisk0 00f6048868b4deee rootvg active

# lspath

Enabled hdisk0 vscsi0

Enabled hdisk0 vscsi1

# lsdev -Cc adapter

ent0 Available Virtual I/O Ethernet Adapter (l-lan)

ent1 Available Virtual I/O Ethernet Adapter (l-lan)

vsa0 Available LPAR Virtual Serial Adapter

vscsi0 Available Virtual SCSI Client Adapter

vscsi1 Available Virtual SCSI Client Adapter

We ensure the adapter is in a Defined state before renaming it. This will fail otherwise.

# rmdev -Rl vscsi1

vscsi1 Defined

# lsdev -Cc adapter | grep vscsi

vscsi0 Available Virtual SCSI Client Adapter

vscsi1 Defined Virtual SCSI Client Adapter

Now we rename the adapter vscsi1 to vscsi3.

# rendev -l vscsi1 -n vscsi3

# lsdev -Cc adapter | grep vscsi

vscsi0 Available Virtual SCSI Client Adapter

vscsi3 Defined Virtual SCSI Client Adapter

That was easy enough. Now I need to bring the adapter and path online with cfgmgr. The lspath output displays an additional path to vscsi3.

# lspath

Enabled hdisk0 vscsi0

Defined hdisk0 vscsi1

# cfgmgr

Method error (/etc/methods/cfgscsidisk -l hdisk0 ):

0514-082 The requested function could only be performed for some

of the specified paths.

# lspath

Enabled hdisk0 vscsi0

Defined hdisk0 vscsi1

Enabled hdisk0 vscsi3

Now I need to remove the old path to vscsi1. The path to vscsi3 is now Enabled. The adapter, vscsi3, is in an Available state. All is good.

# rmpath -l hdisk0 -p vscsi1 -d

path Deleted

# lspath

Enabled hdisk0 vscsi0

Enabled hdisk0 vscsi3

# lsdev -Cc adapter | grep vscsi

vscsi0 Available Virtual SCSI Client Adapter

vscsi3 Available Virtual SCSI Client Adapter

The same steps need to be repeated for the vscsi0 adapter. This is renamed to vscsi2.

# rmdev -Rl vscsi0

vscsi0 Defined

# lsdev -Cc adapter | grep vscsi

vscsi0 Defined Virtual SCSI Client Adapter

vscsi3 Available Virtual SCSI Client Adapter

# rendev -l vscsi0 -n vscsi2

# lsdev -Cc adapter | grep vscsi

vscsi2 Defined Virtual SCSI Client Adapter

vscsi3 Available Virtual SCSI Client Adapter

# lspath

Defined hdisk0 vscsi0

Enabled hdisk0 vscsi3

# cfgmgr

Method error (/etc/methods/cfgscsidisk -l hdisk0 ):

0514-082 The requested function could only be performed for some

of the specified paths.

# lspath

Defined hdisk0 vscsi0

Enabled hdisk0 vscsi2

Enabled hdisk0 vscsi3

# rmpath -l hdisk0 -p vscsi0 -d

path Deleted

# cfgmgr

# lspath

Enabled hdisk0 vscsi2

Enabled hdisk0 vscsi3

That’s it. Both adapters have been renamed while the system was in use. No downtime required.

# lsdev -Cc adapter | grep vscsi

vscsi2 Available Virtual SCSI Client Adapter

vscsi3 Available Virtual SCSI Client Adapter

# lspath

Enabled hdisk0 vscsi2

Enabled hdisk0 vscsi3

Please refer to the AIX 7.1 command reference for more information on this new command:

http://publib.boulder.ibm.com/infocenter/aix/v7r1/topic/com.ibm.aix.cmds/doc/aixcmds4/rendev.htm

And by the way, here’s a draft of what I’ve been working on for the last 5 weeks:

IBM AIX Version 7.1 Differences Guide:

http://www.redbooks.ibm.com/Redbooks.nsf/RedpieceAbstracts/sg247910.html?Open

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In a perfect world....rootvg would always reside on hdisk0.

Renaming devices in AIX 7.1