Swap and Dump Device Configuration Changes

In Oracle Solaris 10 releases, a UFS root environment provides one disk slice for both swap and dump devices. After an Oracle Solaris 11 system is installed, two separate volumes are created as a swap device and a dump device.

# dumpadm
      Dump content: kernel pages
       Dump device: /dev/zvol/dsk/rpool/dump (dedicated)
Savecore directory: /var/crash
  Savecore enabled: yes
   Save compressed: on

# swap -l
swapfile             dev    swaplo   blocks     free
/dev/zvol/dsk/rpool/swap 182,2         8  4061176  4061176

Display information about the swap and dump volume names and sizes. For example:

# zfs list -t volume -r rpool
NAME         USED  AVAIL  REFER  MOUNTPOINT
rpool/dump  4.13G  51.6G  4.00G  -
rpool/swap  4.13G  51.6G  4.00G  -

You can also display swap space sizes in human-readable format. For example:

# swap -sh
total: 1.4G allocated + 227M reserved = 1.6G used, 432G available
# swap -lh
swapfile                   dev    swaplo   blocks     free
/dev/zvol/dsk/rpool/swap 285,2        8K     4.0G     4.0G 

The management of ZFS swap and dump volumes differs from the management of a single slice for a UFS swap and dump device in the following ways:

• You cannot use a single volume for both swap and dump devices in a ZFS root environment

• You cannot use a file as swap device in a ZFS root environment

• The system requires that the dump device is approximately 1/2 to 3/4 the size of physical memory. If the dump device is too small, you will see an error similar to the following:

  # dumpadm -d /dev/zvol/dsk/rpool/dump
  dumpadm: dump device /dev/zvol/dsk/rpool/dump is too small to hold a system dump
  dump size 36255432704 bytes, device size 34359738368 bytes

You can easily increase the size of the dump device by increasing the volume's volsize property, but it might take some time to reinitialize the volume. For example:

# zfs get volsize rpool/dump
NAME        PROPERTY  VALUE  SOURCE
rpool/dump  volsize   1.94G  local
# zfs set volsize=3g rpool/dump
# zfs get volsize rpool/dump
NAME        PROPERTY  VALUE  SOURCE
rpool/dump  volsize   3G     local

Changing the size of the swap volume is difficult if the swap device is in use. Consider creating a second swap volume and adding it as a swap device. For example:

# zfs create -V 3G rpool/swap2
# swap -a /dev/zvol/dsk/rpool/swap2
# swap -l
swapfile             dev    swaplo   blocks     free
/dev/zvol/dsk/rpool/swap 182,2         8  4061176  4061176
/dev/zvol/dsk/rpool/swap2 182,4         8  6291448  6291448

Then, add an entry for the new swap device in the /etc/vfstab file. For example:

/dev/zvol/dsk/rpool/swap2    -        -       swap    -       no      -