Improve documentation of --keep-redundant.

[dss.git] / dss.ggo

diff --git a/dss.ggo b/dss.ggo
index 11529956891db25e5110e03009b88ff5ca36c0c6..5b78ddaa5724e8f6e5ef015613aefb38acf0efdc 100644 (file)
--- a/dss.ggo
+++ b/dss.ggo
@@ -3,7 +3,7 @@
 # Licensed under the GPL v2. For licencing details see COPYING.
 
 package "dss"
-version "0.1.5"
+version "0.1.6"
 purpose "the dyadic snapshot scheduler
 
 dss creates hardlink-based snapshots of a given directory on a remote
@@ -275,22 +275,21 @@ int typestr="days"
 default="4"
 optional
 details="
-       dss snapshot aging is implemented in terms of intervals. There
-       are two command line options related to intervals: the
-       duration u of a \"unit\" interval and the number n of those
-       unit intervals.
-
-       dss removes any snapshots older than n times u and tries to
-       keep 2^(n - k - 1) snapshots in interval k, where the interval
-       number k counts from zero, zero being the most recent unit
-       interval.
-
-       In other words, the oldest snapshot will at most be u * n days
-       (= 20 days if default values are used) old.  Moreover, there
-       are at most 2^n - 1 snapshots in total (i. e. 31 by default).
-       Observe that you have to create at least 2^(n - 1) snapshots
-       each interval for this to work out because that is the number
-       of snapshots in interval zero.
+       Snapshot aging is implemented in terms of intervals. There are two
+       command line options related to intervals: the duration u of a unit
+       interval and the number of unit intervals, denoted n below.
+
+       dss removes snapshots older than n times u and tries to keep 2^(n -
+       k - 1) snapshots in interval k, where the interval number k counts
+       from zero to n - 1, with zero being the most recent unit interval.
+
+       Hence the oldest snapshot will at most be u * n days old (4 days *
+       5 intervals = 20 days, if default values are used). Moreover, there
+       are at most 2^n - 1 snapshots in total (2^5 - 1 = 31 by default). Note
+       that for this to work out your system must be fast enough to create at
+       least 2^(n - 1) snapshots per unit interval (16 snapshots in 4 days =
+       one snapshot in 6 hours), because this is the number of snapshots in
+       interval zero.
 "
 
 option "num-intervals" n
@@ -299,6 +298,10 @@ option "num-intervals" n
 int typestr="num"
 default="5"
 optional
+details="
+       Note that increasing this number by one doubles the total number of
+       snapshots. See the documentation of --unit-interval above.
+"
 
 ###############
 section "Hooks"
@@ -451,13 +454,10 @@ option "keep-redundant" k
 "Prune by disk space only"
 flag off
 details="
-       If this flag is not given dss removes redundant and outdated
-       snapshots automatically.
-
-       Otherwise, this feature is deactivated so that snapshots are
-       only being removed in case disk space or number of free inodes
-       becomes low. Use this flag if the file system containing the
-       destination directory is used for snapshots only.
+       By default, redundant and outdated snapshots are removed automatically
+       to keep the number of snapshots in harmony with the configured
+       policy. If this flag is given, dss removes such snapshots only if
+       disk space or number of free inodes becomes low.
 "
 
 option "min-complete" -