ssgrowd
Copyright 2005 Matt Griswold, dev/IT
Released under the GNU General Public License, see COPYING
Latest version at http://oss.devit.com/matt/#ssgrowd

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# description

ssgrowd is a simple daemon that checks LVM snapshots and grows the diff space
if needed.  It requires both libdevmapper and liblvm.

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# config

check src/config.h for user changable variables:

CHUNK_SZ - size to grow by in megs

THRESHOLD_SZ - megs left on snapshot that will trigger grow

CYCLE_TIME - number of microseconds between checks

In a nutshell, every CYCLE_TIME it checks all LVM snapshots and if the diff
space is less than THRESHOLD_SZ, it extends it by CHUNK_SZ.

The defaults are not heavily tested, I imagine that some tweaking could be in
order.  One thing you'll want to watch for is making sure that you check often
enough and grow by enough that you're growing faster than is possible for your
disc to write.

** WARNING **

While I do use this and haven't encountered a problem yet, I don't claim that
it is without flaw.  If a snapshot overflows it's diff space, it WILL corrupt
the whole snapshot partition, so make sure you set the timing variables
appropiately.

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# installation

LVM2_SRCDIR must be set to the location of your LVM2 source directory, either
edit src/Makefile and set it or pass on the command line to make.  It is used
to link to the static LVM library, so make sure that's built before hand.

add -DDEBUG to CFLAGS for debug information
add -DTIMEXEC to CFLAGS for loop timing

to build it, type
make
or
make LVM2_SRCDIR=<dir>

make install will install ssgrowd to $(prefix)/sbin
ssgrowd.init is a sys v start up script, copy it to /etc/init.d/ssgrowd and
link if you wish to make it run at start up.

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# use

ssgrowd will start the daemon and fork into the background.  To see the command
line options, use ssgrowd --help.

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# contact

Questions, comments, bugs, etc.

Matt Griswold <matt@devit.com> 0x6B2E514F
6CF4 A97B 55A5 BBD6 FF06  6F0B F99D 7C86 6B2E 514F
http://oss.devit.com/matt/