'\" te
.\" Copyright (c) 2012 by Delphix. All rights reserved.
+.\" Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
.\" The contents of this file are subject to the terms of the Common Development
.\" and Distribution License (the "License"). You may not use this file except
.\" in compliance with the License. You can obtain a copy of the license at
.\" CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your
.\" own identifying information:
.\" Portions Copyright [yyyy] [name of copyright owner]
-.TH ZPOOL-FEATURES 5 "Mar 16, 2012"
+.TH ZPOOL-FEATURES 5 "Feb 4, 2013"
.SH NAME
zpool\-features \- ZFS pool feature descriptions
.SH DESCRIPTION
.LP
ZFS pool on\-disk format versions are specified via "features" which replace
the old on\-disk format numbers (the last supported on\-disk format number is
-28). To enable a feature on a pool use the \fBzpool\fR(1M) command to set
-the \fBfeature@\fR\fIfeature_name\fR property to \fBenabled\fR.
+28). To enable a feature on a pool use the \fBupgrade\fR subcommand of the
+\fBzpool\fR(8) command, or set the \fBfeature@\fR\fIfeature_name\fR property
+to \fBenabled\fR.
.sp
.LP
The pool format does not affect file system version compatibility or the ability
software's ability to read from the pool. These features are referred to as
"read\-only compatible". If all unsupported features on a pool are read\-only
compatible, the pool can be imported in read\-only mode by setting the
-\fBreadonly\fR property during import (see \fBzpool\fR(1M) for details on
+\fBreadonly\fR property during import (see \fBzpool\fR(8) for details on
importing pools).
.SS "Unsupported features"
.sp
This feature is only \fBactive\fR while \fBfreeing\fR is non\-zero.
.RE
+
+.sp
+.ne 2
+.na
+\fB\fBempty_bpobj\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID com.delphix:empty_bpobj
+READ\-ONLY COMPATIBLE yes
+DEPENDENCIES none
+.TE
+
+This feature increases the performance of creating and using a large
+number of snapshots of a single filesystem or volume, and also reduces
+the disk space required.
+
+When there are many snapshots, each snapshot uses many Block Pointer
+Objects (bpobj's) to track blocks associated with that snapshot.
+However, in common use cases, most of these bpobj's are empty. This
+feature allows us to create each bpobj on-demand, thus eliminating the
+empty bpobjs.
+
+This feature is \fBactive\fR while there are any filesystems, volumes,
+or snapshots which were created after enabling this feature.
+.RE
+
+.sp
+.ne 2
+.na
+\fB\fBlz4_compress\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID org.illumos:lz4_compress
+READ\-ONLY COMPATIBLE no
+DEPENDENCIES none
+.TE
+
+\fBlz4\fR is a high-performance real-time compression algorithm that
+features significantly faster compression and decompression as well as a
+higher compression ratio than the older \fBlzjb\fR compression.
+Typically, \fBlz4\fR compression is approximately 50% faster on
+compressible data and 200% faster on incompressible data than
+\fBlzjb\fR. It is also approximately 80% faster on decompression, while
+giving approximately 10% better compression ratio.
+
+When the \fBlz4_compress\fR feature is set to \fBenabled\fR, the
+administrator can turn on \fBlz4\fR compression on any dataset on the
+pool using the \fBzfs\fR(8) command. Please note that doing so will
+immediately activate the \fBlz4_compress\fR feature on the underlying
+pool (even before any data is written). Since this feature is not
+read-only compatible, this operation will render the pool unimportable
+on systems without support for the \fBlz4_compress\fR feature. At the
+moment, this operation cannot be reversed. Booting off of
+\fBlz4\fR-compressed root pools is supported.
+
+.RE
+
.SH "SEE ALSO"
-\fBzpool\fR(1M)
+\fBzpool\fR(8)
git://git.camperquake.de / zfs.git / blobdiff