Reducing Storage Costs with ZFS Compression

This blog describes how to use ZFS compression as a simple and flexible way to reduce the power, cooling, and floor space costs that are associated with storing data.

Oracle Solaris 11.3 includes lz4 compression. You can display supported compression algorithms on your system like this: 

# zfs help compression
compression (property)
Editable, Inheritable
Accepted values: on | off | lzjb | gzip | gzip-[1-9] | zle | lz4

When ZFS compression is enabled on a file system, all newly written data is compressed. If you are storing new, compressible data, the syntax is simple:

# zfs create -o compression=on tank/data

ZFS file system properties are flexible because you can set them on an individual file system or an entire pool. For example:

# zfs set compression=on pond

The above syntax means that all newly written data to this pool is compressed.

If you have compressible data but are concerned about the impact on system resources, consider trying lz4 compression. For example:

# zfs create -o compression=lz4 tank/cdata
cannot create 'tank/cdata': pool must be upgraded to set this property
or value

This error means that the pool version needs to be updated to pool version 37 to support lz4 compression.

# zpool upgrade tank
This system is currently running ZFS pool version 37.

Successfully upgraded 'tank' from version 35 to version 37

# zfs create -o compression=lz4 tank/cdata

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 More clarification added around root pool behavior:

Currently, neither gzip nor lz4 compression is supported on root pools. If you attempt to set either gzip or lz4 compression on the current BE file system, you see an error similar to the following:

# zfs set compression=lz4 rpool/ROOT/s11u3

cannot set property for 'rpool/ROOT/s11u3': property setting is not
allowed on bootable datasets 

If you set either gzip or lz4 compression on a root pool, no error occurs. (I filed a bug about this). If you attempt to pkg update the current BE, the operation eventually fails. You will see a message similar to this:

BootmgmtError: operation not supported on this type of pool

Use the following steps to recover:

 1. Set default compression (lzjb) on the root pool:

# zfs set compression=on rpool

2. Remove the BE that was created during the (failed) pkg update process.

# beadm destroy s11u3-1 

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In summary, ZFS compression is simple, flexible, and can reduce your storage footprint.

Solaris customers are reporting compression ratios in the 2X - 15X range, depending on their workloads, which can translate into huge cost savings. Give it a try.