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and geom_uncompress(4): 1. mkuzip(8): - Proper support for eliminating all-zero blocks when compressing an image. This feature is already supported by the geom_uzip(4) module and CLOOP format in general, so it's just a matter of making mkuzip(8) match. It should be noted, however that this feature while it sounds great, results in very slight improvement in the overall compression ratio, since compressing default 16k all-zero block produces only 39 bytes compressed output block, which is 99.8% compression ratio. With typical average compression ratio of amd64 binaries and data being around 60-70% the difference between 99.8% and 100.0% is not that great further diluted by the ratio of number of zero blocks in the uncompressed image to the overall number of blocks being less than 0.5 (typically). However, this may be important from performance standpoint, so that kernel are not spinning its wheels decompressing those empty blocks every time this zero region is read. It could also be important when you create huge image mostly filled with zero blocks for testing purposes. - New feature allowing to de-duplicate output image. It turns out that if you twist CLOOP format a bit you can do that as well. And unlike zero-blocks elimination, this gives a noticeable improvement in the overall compression ratio, reducing output image by something like 3-4% on my test UFS2 3GB image consisting of full FreeBSD base system plus some of the packages (openjdk, apache etc), about 2.3GB worth of file data (800+MB compressed). The only caveat is that images created with this feature "on" would not work on older versions of FeeBSDxi kernel, hence it's turned off by default. - provide options to control both features and document them in manual page. - merge in all relevant LZMA compression support from the mkulzma(8), add new option to select between both. - switch license from ad-hoc beerware into standard 2-clause BSD. 2. geom_uzip(4): - implement support for de-duplicated images; - optimize some code paths to handle "all-zero" blocks without reading any compressed data; - beef up manual page to explain that geom_uzip(4) is not limited only to md(4) images. The compressed data can be written to the block device and accessed directly via magic of GEOM(4) and devfs(4), including to mount root fs from a compressed drive. - convert debug log code from being compiled in conditionally into being present all the time and provide two sysctls to turn it on or off. Due to intended use of the module, it can be used in environments where there may not be a luxury to put new kernel with debug code enabled. Having those options handy allows debug issues without as much problem by just having access to serial console or network shell access to a box/appliance. The resulting additional CPU cycles are just few int comparisons and branches, and those are minuscule when compared to data decompression which is the main feature of the module. - hopefully improve robustness and resiliency of the geom_uzip(4) by performing some of the data validation / range checking on the TOC entries and rejecting to attach to an image if those checks fail. - merge in all relevant LZMA decompression support from the geom_uncompress(4), enable automatically when appropriate format is indicated in the header. - move compilation work into its own worker thread so that it does not clog g_up. This allows multiple instances work in parallel utilizing smp cores. - document new knobs in the manual page. Reviewed by: adrian MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D5333
180 lines
5.0 KiB
Groff
180 lines
5.0 KiB
Groff
.\"
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.\" Copyright (c) 2006 Ceri Davies
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd October 9, 2006
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.Dt GEOM_UZIP 4
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.Os
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.Sh NAME
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.Nm geom_uzip
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.Nd "GEOM based compressed disk images and partitions"
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.Sh SYNOPSIS
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To compile this driver into the kernel,
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place the following line in your
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kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "options GEOM_UZIP"
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.Ed
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.Pp
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Alternatively, to load the driver as a
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module at boot time, place the following line in
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.Xr loader.conf 5 :
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.Bd -literal -offset indent
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geom_uzip_load="YES"
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.Ed
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.Sh DESCRIPTION
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The
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.Nm
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framework provides support for compressed read-only
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disk images.
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This allows significant storage savings at the expense of
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a some CPU time on each read.
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Data written in the GEOM label area allows
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.Nm
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to detect compressed images which have been created with
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.Xr mkuzip 8
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and presented to the kernel as a logical disk device via
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.Xr md 4 .
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.Nm
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creates a unique
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.Pa md#.uzip
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device for each image.
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.Pp
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.Nm
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is not limited to supporting only
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.Xr md 4
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images.
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The image can also reside on a block device.
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.Pq For example, a disk, USB flash drive, DVD-ROM, etc.
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The appropriate device node will appear with the
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.Pa .uzip
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suffix.
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.Bd -literal -offset indent
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# gpart show da0
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=> 0 7833600 da0 BSD (3.7G)
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0 2097152 1 freebsd-ufs (1.0G)
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2097152 5736448 - free - (2.7G)
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# gpart add -t freebsd-ufs -s 1G da0
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da0b added
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# dd if=/tmp/20160217_dcomp_zcomp.uzip bs=256k of=/dev/da0b
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3190+1 records in
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3190+1 records out
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836331008 bytes transferred in 111.021489 secs (7533055 bytes/sec)
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# fsck -t ffs /dev/da0b.uzip
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** /dev/da0b.uzip (NO WRITE)
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** Last Mounted on /mnt
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** Phase 1 - Check Blocks and Sizes
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** Phase 2 - Check Pathnames
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** Phase 3 - Check Connectivity
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** Phase 4 - Check Reference Counts
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** Phase 5 - Check Cyl groups
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97455 files, 604242 used, 184741 free (2349 frags, 22799 blocks,
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0.3% fragmentation)
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# mount -o ro /dev/da0b.uzip /mnt
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# df /dev/da0b.uzip
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Filesystem 1K-blocks Used Avail Capacity Mounted on
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/dev/da0b.uzip 3155932 2416968 738964 77% /mnt
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.Ed
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.Pp
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The
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.Nm
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device is subsequently used by
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.Fx
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kernel to access the uncompressed data.
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The
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.Nm
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driver does not allow write operations to the underlying disk image.
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To check which
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.Dq providers
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match a given
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.Nm
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device:
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.Bd -literal -offset indent
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# geom uzip list
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Geom name: md1.uzip
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Providers:
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1. Name: md1.uzip
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Mediasize: 22003712 (21M)
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Sectorsize: 512
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Consumers:
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1. Name: md1
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Mediasize: 9563648 (9.1M)
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Sectorsize: 512
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Geom name: da0b.uzip
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Providers:
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1. Name: da0b.uzip
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Mediasize: 3355443200 (3.1G)
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Sectorsize: 512
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Consumers:
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1. Name: da0b
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Mediasize: 1073741824 (1.0G)
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Sectorsize: 512
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.Ed
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.Pp
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.Nm
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allows mounting the root file system from a compressed disk partition by
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setting the
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.Dv vfs.root.mountfrom
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tunable.
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See
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.Xr loader.conf 5
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for details.
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.Sh DIAGNOSTICS
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Several flags are provided for tracing
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.Nm
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I/O operations and TOC parsing via the following sysctls.
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.Bl -tag -width indent
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.It Va kern.geom.uzip.debug
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Log level.
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Zero disables logging.
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Higher values enable more verbose debug logging for
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.Nm .
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Supported levels are from 0 (no logging) to 4 (maximum amount of logging).
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.It Va kern.geom.uzip.debug_block
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Log operations involving compressed cluster number.
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.El
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.Sh SEE ALSO
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.Xr GEOM 4 ,
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.Xr md 4 ,
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.Xr geom 8 ,
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.Xr mkuzip 8
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.Sh AUTHORS
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.An -nosplit
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The
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.Nm
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driver was written by
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.An Max Khon Aq Mt fjoe@FreeBSD.org .
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The block de-duplication code as well as some
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.Nm
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driver optimizations have been contributed by
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.An Maxim Sobolev Aq Mt sobomax@FreeBSD.org .
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The LZMA decompression support and CLOOP 3.0 support have been added by
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.An Aleksandr Rybalko Aq Mt ray@FreeBSD.org .
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.Pp
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This manual page was written by
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.An Ceri Davies Aq Mt ceri@FreeBSD.org .
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