Package: zfsutils Version: 8.1-3 Tags: patch Compression in ZFS has a triple benefit in IO performance, disk space and energy consumption, this article explains (with benchmarks): http://blogs.sun.com/partnertech/entry/zfs_compression_perf_disk_space
IO improvement isn't obvious: reading and writing takes less time when compressing or decompressing because CPU is not the bottleneck. The linked article explains in more detail. I suggest enabling compression by default when creating new ZFS filesystems.
--- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/zio.h 2010-05-24 06:09:36.000000000 -0400 +++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/zio.h 2010-08-19 18:52:33.995673472 -0400 @@ -98,7 +98,7 @@ }; #define ZIO_COMPRESS_ON_VALUE ZIO_COMPRESS_LZJB -#define ZIO_COMPRESS_DEFAULT ZIO_COMPRESS_OFF +#define ZIO_COMPRESS_DEFAULT ZIO_COMPRESS_ON #define ZIO_FAILURE_MODE_WAIT 0 #define ZIO_FAILURE_MODE_CONTINUE 1