Backup strategy discussions. db_recover example to do.

doc/guide/admin/maintenance.sdf

@@ -10,7 +10,40 @@ discuss how to correctly maintain an OpenLDAP deployment.
 
 H2: Directory Backups
 
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+Backup strategies largely depend on the amount of change in the database
+and how much of that change an administrator might be willing to lose in a 
+catastrophic failure. There are two basic methods that can be used:
+
+1. Backup the Berkeley database itself and periodically back up the transaction 
+log files:
+
+Berkeley DB produces transaction logs that can be used to reconstruct
+changes from a given point in time. For example, if an administrator were willing to only
+lose one hour's worth of changes, they could take down the server in
+the middle of the night, copy the Berkeley database files offsite, and bring
+the server back online. Then, on an hourly basis, they could force a
+database checkpoint, capture the log files that have been generated in the
+past hour, and copy them offsite. The accumulated log files, in combination
+with the previous database backup, could be used with db_recover to
+reconstruct the database up to the time the last collection of log files was
+copied offsite. This method affords good protection, with minimal space
+overhead.
+
+
+2. Periodically run slapcat and back up the LDIF file:
+
+Slapcat can be run while slapd is active. However, one runs the risk of an
+inconsistent database- not from the point of slapd, but from the point of
+the applications using LDAP. For example, if a provisioning application
+performed tasks that consisted of several LDAP operations, and the slapcat
+took place concurrently with those operations, then there might be
+inconsistencies in the LDAP database from the point of view of that
+provisioning application and applications that depended on it. One must,
+therefore, be convinced something like that won't happen. One way to do that
+would be to put the database in read-only mode while performing the
+slapcat. The other disadvantage of this approach is that the generated LDIF
+files can be rather large and the accumulation of the day's backups could
+add up to a substantial amount of space.
 
 You can use {{slapcat}}(8) to generate an LDIF file for each of your {{slapd}}(8) 
 back-bdb or back-hdb databases.
@@ -19,8 +52,7 @@ back-bdb or back-hdb databases.
 
 For back-bdb and back-hdb, this command may be ran while slapd(8) is running.
 
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+MORE on actual Berkeley DB backups later covering db_recover etc.
 
 H2: Berkeley DB Logs