Working With Disksets

This section describes maintenance tasks for disksets, including reserving and releasing disksets, and adding hosts and disks to a diskset.

Preliminary Information for Working With Disksets

• To perform maintenance on a diskset, a host must be the owner of the diskset or have reserved the diskset. (A host takes implicit ownership of the diskset by putting the first drives into the set.)

• To work with a diskset, root must be a member of Group 14, or the ./rhosts file must contain an entry for the other hostname (on each host).

How to Reserve a Diskset (Command Line)

Disksets can be reserved safely or forcibly. When one host in a diskset reserves the diskset, the other host in the diskset cannot access data on drives in the diskset.

• Safely - Reserves the diskset for your host only if no other host has reserved the diskset.

• Forcibly - Reserves the diskset whether or not another host currently has the set reserved. Use this method when a host in the diskset is down or not communicating. If the other host had the diskset reserved at this point, it would panic due to reservation loss.

If you are fairly certain that the hosts in the diskset are communicating, it is normally a good idea to perform a safe reservation.

Make sure you have met the prerequisites ("Prerequisites for Maintaining DiskSuite Objects") and have read the preliminary information ("Preliminary Information for Working With Disksets"). Use the metaset(1M) to reserve a diskset safely or forcibly. For more information, refer to the metaset(1M) man page.

If another host has ownership of the diskset, it will panic due to a SCSI reservation conflict.

Example -- Reserving a Diskset Safely

red# metaset
...
Set name = relo-red, Set number = 2
 
Host                Owner
  red
  blue
...
red# metaset -s relo-red -t
red# metaset
...
Set name = relo-red, Set number = 2
 
Host                Owner
  red                Yes
  blue
...

In this example, host red communicates with host blue and ensures that host blue has released any reservation of the diskset before host red attempts to reserve the set.

In this example, if host blue owned the set relo-red, the "Owner" column in the above output would still have been blank. The metaset(1M) command only shows whether the issuing host owns the diskset, and not the other host.

Example -- Reserving a Diskset Forcibly

# metaset -s relo-red -t -f

In this example, host red does not communicate with host blue. Instead, the drives in the diskset are reserved without warning. If host blue had the diskset reserved, it would now panic due to reservation loss.

How to Release a Diskset (Command Line)

Releasing a diskset is useful when performing maintenance on the drives in the set. When a diskset is released, it cannot be accessed by the host. If both hosts in a diskset release the set, neither host in the diskset can access metadevices or hot spare pools defined in the set.

1. Make sure you have met the prerequisites ("Prerequisites for Maintaining DiskSuite Objects") and have read the preliminary information ("Preliminary Information for Working With Disksets").

2. Release the diskset by using the metaset(1M) command

   # metaset -s diskset -r

   In this command,

   -s diskset	Specifies the name of a diskset on which metaset will work.
   -r	Releases ownership of a diskset. The reservation of all the disks within the set is removed. The metadevices set up within the set are no longer accessible.

3. Verify that the diskset has been released on this host by using the metaset(1M) command without any options.

   # metaset

Example -- Releasing a Diskset

red# metaset -s relo-red -r
red# metaset -s relo-red
 
Set name = relo-red, Set number = 1
 
Host                Owner
  red
  blue
 
Drive               Dbase
  c1t0d1             Yes
  c1t2d0             No 
  c1t3d0             No 
  c1t4d1             No 
  c2t2d0             Yes
  c3t0d1             Yes
  c3t2d0             No 
  c3t3d0             No 
  c3t4d1             No 

This example releases the diskset relo-red. Note that there is no owner of the diskset. Viewing status from host red could be misleading. A host can only determine if it does or does not own a diskset. For example, if host blue were to reserve the diskset, it would not appear so from host red; only host blue would be able to determine the reservation in this case.

How to Add Additional Drives to a Diskset (Command Line)

You can add drives to a diskset after it has been defined.

1. Make sure you have met the prerequisites ("Prerequisites for Maintaining DiskSuite Objects") and have read the preliminary information ("Preliminary Information for Working With Disksets").

2. Add a drive to an existing diskset by using the metaset(1M) command.

   # metaset -s diskset -a drivename ...

   In this command,

   -s diskset	Specifies the name of a diskset on which metaset will work.
   -a	Adds drives to the named diskset.
   drivename...	Specifies the drives to add to the diskset. Drive names are in the form cxtxdx; no "sx" slice identifiers are at the end of the name. The drivename must have the same major and minor names on all hosts in the diskset.

   When drives are added to a diskset, DiskSuite re-balances the metadevice state database replicas across the remaining drives. Refer to "Creating Disksets" for more information.

   ---

   Caution -

   You will lose data if you add drives that contain data.

   ---

3. Verify that the host has been added to the diskset by using the metaset(1M) command without any options.

   # metaset

Example -- Adding Additional Drives to a Diskset

red# metaset -s relo-red -a c2t5d0
red# metaset
Set name = relo-red, Set number = 1
 
Host                Owner
  red                Yes
  blue
 
Drive               Dbase
  c1t2d0             Yes
  c1t3d0             Yes
  c2t2d0             Yes
  c2t3d0             Yes
  c2t4d0             Yes
  c2t5d0             No

This example adds drive c2t5d0 to diskset relo-red.

If you add or delete drives to a diskset while DiskSuite Tool is running, a dialog box appears stating that the configuration has changed. Either reload the configuration by selecting Rescan Configuration from the File menu, or exit DiskSuite Tool then restart it.

How to Add Another Host to a Diskset (Command Line)

DiskSuite supports a maximum of two hosts per diskset. You can add another host to an existing diskset that only has one host.

1. Make sure you have met the prerequisites ("Prerequisites for Maintaining DiskSuite Objects") and have read the preliminary information ("Preliminary Information for Working With Disksets").

2. Add the host:

   # metaset -s diskset -a -h host ...

   In this command,

   -s diskset	Specifies the name of a diskset on which metaset will work.
   -a	Adds hosts to the named diskset.
   -h host...	Specifies one or more hostnames to be added to the diskset. Adding the first host creates the set. The hostname is the same name found in /etc/nodename.

3. Verify that the host has been added to the diskset by using the metaset(1M) command without any options.

   # metaset

Example -- Adding Another Host to a Diskset

red# metaset -s relo-red -a -h blue
red# metaset -s relo-red
Set name = relo-red, Set number = 1
 
Host                Owner
  red                Yes
  blue
 
Drive               Dbase
  c1t0d1             Yes
  c1t2d0             No 
  c1t3d0             No 
  c1t4d1             No 
  c2t2d0             Yes
  c3t0d1             Yes
  c3t2d0             No 
  c3t3d0             No 
  c3t4d1             No 

This example adds host blue to the diskset relo-red.