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i-rinat committed Jan 12, 2013
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.\" Copyright 2013 Rinat Ibragimov
.TH reiserfs-defrag 8 "January 2013" ""
reiserfs-defrag \- offline defragmenting utility for reiserfs v3.6
.B reiserfs-defrag
[ options ]
.I partition
\fBreiserfs-defrag\fR is utility that rearranges data on reiserfs partition to
increase its read/write performace.
While beeing offline, it uses filesystem journal to ensure sudden interruption
not to damage fs. By default it journals only metadata but writes them only
after actual data update, (similar to data=ordered option of ext3/4). Full
data journaling can be forced as well.
You can safely interrupt \fBreiserfs-defrag\fR by pressing ^C or sending SIGINT signal.
It will finish current operation and exit. May take couple of minutes.
is either special device or file containing reiserfs filesystem.
\fB-c\fR | \fB--cache-size\fR \fIsize\fR
Specify size of cache size in MiBs. All read blocks are placed in cache to avoid
reading them twice. Default value of 200 MiB is trade-off between read performance
and memory consuption. If you have more RAM available, increase this. Note, however,
that memory usage is sligtly more than cache size itself usually.
\fB-f\fR | \fB--file-list\fR \fI file-list\fR
Move files listed in \fIfile-list\fR to beginning of the partition, while preserving
their order. This can be used to speedup \fBreadahead(8)\fR by placing files together
in fastest disk area.
\fB-h\fR | \fB--help\fR
Display usage and exit.
Enable full data journaling, not only journaling metadata. Usually this is overkill
due to non-destructive operation. Significantly decreases performance.
\fB-p\fR \fIpass-count\fR
Specify pass count for incremental defragmentation algorithm. Usually one or two passes
will suffice, three are by default. You can increase it, but \fBreiserfs-defrag\fR will
exit if no further passes needed.
\fB-s\fR | \fB--squeeze\fR
Compact allocation blocks to increase free extent sizes. This is done on per allocation
group basis. Allocation group will be treated if its free extent count exceeds threshold
(7 by default).
\fB--squeeze-threshold\fR \fIvalue\fR
Specify threshold of allocation group free extent count. Note: you must specify one of
\fB-s\fR or \fB--squeeze\fR to actually enable squeezing.
\fB-t\fR | \fB--type\fR \fItype\fR
Select defragmentation algorithm. There are three of them:
.IP \ 8
* \fInone\fR perform no defragmentation. Useful, if you want just squeeze;
.IP \ 8
* \fItree-through\fR, \fItreethrough\fR or \fItree\fR pack whole tree contents.
First it packs all internal nodes, then leaf nodes interleaved with data blocks.
This algorithm will move most of filesystem contents (almost twice) and therefore
will be slow. At the end you will have all your data packed tightly, without gaps
between them, and all your free space consolidated at the end of partition. Note that
you can't get continous free space larger than 128 MiB because of bitmap blocks
scattered across partition.
.IP \ 8
* \fIinc\fR or \fIincremental\fR (selected by default) performs incremental
defragmentation. It scans all files and moves only their fragmented parts. During operation
it will make some room as needed. Such cleaning can move continuous files away from
their positions. This potentially can lead to increasing fragmentation, but algorithm
takes care of that by doing multiple passes.
Rinat Ibragimov <>
Please report bugs to \fI\fR
To simplify debugging you can provide output of \fIdebugreiserfs -p /dev/your-partition\fR.
Binary stream will contain file names, their sizes and positions but not their content,
i.e. enough information to recreate structure of your partition.
Little-endian only.
Old copies of data are not cleared. That can interfere with emergency rebuild-tree
operation of \fBreiserfsck(8)\fR, although it is not verified.
reiserfsck(8), debugreiserfs(8), readahead(8)

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