This is a little bit of a rant, so be prepared.<\/p>\n
I have lost count of the number of times I come across people in the \u201cbiz\u201d who tell clients, or anyone else who will listen, that replication is the same as backup.\u00a0 It most emphatically is not<\/em><\/strong>!\u00a0 To tell somebody that is to tell a lie, pure an simple.<\/p>\n Backup and replication can be equal parts of an overall DR strategy but they are very different animals and do very different things for very different reasons.<\/p>\n A backup is a \u201csnapshot in time\u201d of the state of files and\/or a system.\u00a0 It is a static picture of how things are at the point in time that the backup is taken.\u00a0 Once the backup is taken it should be immutable, unchanging.\u00a0 It is as things \u201cwere\u201d, not how they \u201care\u201d.<\/p>\n Replication, on the other hand, is fluid.\u00a0 By definition, if I am replicating from one system to another then I am copying the continually changing state of system \u201cA\u201d to system \u201cB\u201d.\u00a0\u00a0 If I add a file to \u201cA\u201d it should show up in the same place on \u201cB’\u201d, possibly in near realtime.\u00a0 If I delete the same file on \u201cA\u201d then it will be removed from \u201cB\u201d.\u00a0 I cannot rely on \u201cB\u201d having a copy of a file that has been deleted from \u201cA\u201d nor can I rely on \u201cB\u201d having an unchanged copy of a file that has been modified on \u201cA\u201d.\u00a0 As can be surmised, replication is as things \u201care\u201d, not as they \u201cwere\u201d.<\/p>\n Backups save your butt when things screw up and files and\/or systems get trashed.\u00a0 Backups help all of us save face in the case of the file delete \u201coopsie\u201d.\u00a0 Backups let us get back to a known point in time, if needs be.\u00a0 And, yes, backups can allow us to recover full systems albeit usually with moderate to significant time lag.\u00a0 Backup is all about \u201crecovery\u201d.<\/p>\n Replication can ensure that data is always available because more than one current copy exists and can be made accessible.\u00a0 It is about having the ability to \u201cfail over\u201d to another system because everything that is needed is available in more than one place.\u00a0 Replication is all about continuity and availability.<\/p>\n The definitions I have given here may be a bit simplistic but you should get the drift.\u00a0 And remember, replication \u2260 backup; backup \u2260 replication.<\/p>\n","protected":false},"excerpt":{"rendered":"