Managing Your ZFS Swap and Dump Devices

During the installation process, a swap area is created on a ZFS volume in the ZFS root pool. For example:

# swap -l
swapfile                  dev    swaplo   blocks     free
/dev/zvol/dsk/rpool/swap 145,2        16 16646128 16646128

During the installation process, a dump device is created on a ZFS volume in the ZFS root pool. In general, a dump device requires no administration because it is setup automatically at installation time. For example:

# dumpadm
      Dump content: kernel pages
       Dump device: /dev/zvol/dsk/rpool/dump (dedicated)
Savecore directory: /var/crash/t5120
  Savecore enabled: yes
   Save compressed: on

If you disable and remove the dump device, then you will need to enable it with the dumpadm command after it is recreated. In most cases, you will only have to adjust the size of the dump device by using the zfs command.

For information about the swap and dump volume sizes that are created by the installation programs, see Oracle Solaris 11 Express Installation Requirements for ZFS Support.

Both the swap volume size and the dump volume size can be adjusted after installation. For more information, see Adjusting the Sizes of Your ZFS Swap and Dump Devices.

Consider the following issues when working with ZFS swap and dump devices:

Separate ZFS volumes must be used for the swap area and dump devices.
Currently, using a swap file on a ZFS file system is not supported.
If you need to change your swap area or dump device after the system is installed or upgraded, use the swap and dumpadm commands as in previous Solaris releases. For more information, see Chapter 21, Configuring Additional Swap Space (Tasks), in System Administration Guide: Devices and File Systems and Chapter 13, Managing System Crash Information (Tasks), in System Administration Guide: Common System Management Tasks.

Adjusting the Sizes of Your ZFS Swap and Dump Devices

You might need to adjust the size of swap and dump devices after installation or possibly, recreate the swap and dump volumes.

Adjust the size of your swap and dump volumes.

You can reset the volsize property of the dump device after a system is installed. For example:

# zfs set volsize=2G rpool/dump
# zfs get volsize rpool/dump
NAME        PROPERTY  VALUE       SOURCE
rpool/dump  volsize   2G          -

You can resize the swap volume but until CR 6765386 is integrated, it is best to remove the swap device first. Then, recreate it. For example:
```
# swap -d /dev/zvol/dsk/rpool/swap
# zfs volsize=2G rpool/swap
# swap -a /dev/zvol/dsk/rpool/swap
```
For information on removing a swap device on an active system, see this site:

http://www.solarisinternals.com/wiki/index.php/ZFS_Troubleshooting_Guide

If you need more swap space on a system that is already installed, just add another swap volume. For example:

# zfs create -V 2G rpool/swap2

Then, activate the new swap volume. For example:

# swap -a /dev/zvol/dsk/rpool/swap2
# swap -l
swapfile                  dev  swaplo   blocks   free
/dev/zvol/dsk/rpool/swap  256,1      16 1058800 1058800
/dev/zvol/dsk/rpool/swap2 256,3      16 4194288 4194288

Add an entry for the second swap volume to the /etc/vfstab file.

Select one of the following if you need to recreate your swap area:
- On a SPARC based system, create your swap area. Set the block size to 8 KB.
```
# zfs create -V 2G -b 8k rpool/swap
```
- On an x86 based system, create your swap area. Set the block size to 4 KB.
```
# zfs create -V 2G -b 4k rpool/swap
```
You must enable the swap area when a new swap device is added or changed.
Add an entry for the swap volume to the /etc/vfstab file.

Troubleshooting ZFS Dump Device Issues

Review the following items if you have problems either capturing a system crash dump or resizing the dump device.

If a crash dump was not created automatically, you can use the savecore command to save the crash dump.
A dump device is created automatically when you initially install a ZFS root file system or migrate to a ZFS root file system. In most cases, you will only need to adjust the size of the dump device if the default dump device size is too small. For example, on a large-memory system, the dump device size is increased to 40 GB as follows:
```
# zfs set volsize=40G rpool/dump
```
Resizing a large dump device can be a time-consuming process.

If, for any reason, you need to enable a dump device after you create a dump device manually, use syntax similar to the following:
```
# dumpadm -d /dev/zvol/dsk/rpool/dump
      Dump content: kernel pages
       Dump device: /dev/zvol/dsk/rpool/dump (dedicated)
Savecore directory: /var/crash/t5120
  Savecore enabled: yes
   Save compressed: on
```
A system with 128 GB or greater memory will need a larger dump device than the dump device that is created by default. If the dump device is too small to capture an existing crash dump, a message similar to the following is displayed:
```
# 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
```
For information on sizing the swap and dump devices, see Planning for Swap Space in System Administration Guide: Devices and File Systems.
You cannot currently add a dump device to a pool with multiple top level-devices. You will see a message similar to the following:
```
# dumpadm -d /dev/zvol/dsk/datapool/dump 
   dump is not supported on device '/dev/zvol/dsk/datapool/dump': 'datapool' has multiple top level vdevs
```
Add the dump device to the root pool, which cannot have multiple top-level devices.

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