Have I got my Macrium differentials right?

Stevekir said:

1. During the week there will be four Diffs made at equal intervals of 1.75 days (7/4 = 1.75).

No. You can set backups to be made monthly, weekly, every day, every specific week day or every X days where X is an integer (1, 2, 3 etc.). It can't be a fraction (1.75, 0.6, 2.5 etc.).

Stevekir said:

2. The first Diff. will record all the changes since the Full backup was made; the second will also record all the changes since the Full was made and so on.

Yes. A differential image backs up changes since last full backup, an incremental image changes since last full, differential or incremental backup.

Stevekir said:

3. At the end of a normal week the Full and the Diffs would be deleted and a new Full immediately created, with the new Diffs created in turn during that new week.

Let's call subsequent full backups as Full1, Full2, Full3 and so on, and respectively differential backups as Diff1, Diff2, Diff3 and so on.

You have a backup schedule to make a full backup once a week and a differential every second day. Retention rules are set to keep one full and four differentials.

According to your sample backup definition, Full1 will be deleted when Full2 will be created, Diff1 will be deleted when Diff5 will be created, and so on.

• Week 1, Day 1, a full backup Full1 will be made, followed by differentials Diff1 on Day 3, Diff2 on Day 5 and Diff3 on Day 7
• Week 2, Day 1 a new Full2 will be created and according to retention rules, Full1 will be deleted
• Diff1, Diff2 and Diff3 will now become obsolete and useless; they could no longer be used to restore Windows because to restore a differential image its parent full image is required
• Based on above, you should change retention rules so that a full backup is kept until its last child backup (differential or incremental) is deleted, in this example case if you only want to keep differentials for one week and you create a full every week, you should keep two full backups, deleting Full1 only when Full3 will be created and last child differential of Full1 will be deleted

Stevekir said:

4. If during the week a crash occured and the computer was re-booted, the last Diff created before the crash would be double-clicked on and the Full backup would be updated to the time/date of that last Diff.

No. Full image would not be updated. You just begin restore process selecting the last differential as image to be restored, it then uses its parent full image as base restoring it, then applying changes in itself.

Stevekir said:

5. That updated Full Backup could then be used to restore the computer to the position it was in when the last Diff.was created.

No. See above.

Stevekir said:

6. This is the reason for creating Diffs. and the only reason.

You create differential and incremental images because they will be made faster and will be smaller than full backups.

Kari

ok

Kari said:

No. You can set backups to be made monthly, weekly, every day, every specific week day or every X days where X is an integer (1, 2, 3 etc.). It can't be a fraction (1.75, 0.6, 2.5 etc.).




Yes. A differential image backs up changes since last full backup, an incremental image changes since last full, differential or incremental backup.






Let's call subsequent full backups as Full1, Full2, Full3 and so on, and respectively differential backups as Diff1, Diff2, Diff3 and so on.

You have a backup schedule to make a full backup once a week and a differential every second day. Retention rules are set to keep one full and four differentials.

• Week 1, Day 1, a full backup Full1 will be made, followed by differentials Diff1 on Day 3, Diff2 on Day 5 and Diff3 on Day 7
• Week 2, Day 1 a new Full2 will be created and according to retention rules, Full1 will be deleted
• Diff1, Diff2 and Diff3 will now become obsolete and useless; they could no longer be used to restore Windows because to restore a differential image its parent full image is required
• Based on above, you should change retention rules so that a full backup is kept until its last child backup (differential or incremental) is deleted, in this example case if you only want to keep differentials for one week and you create a full every week, you should keep two full backups, deleting Full1 only when Full3 will be created and last child differential of Full1 will be deleted

No. Full image would not be updated. You just begin restore process selecting the last differential as image to be restored, it then uses its parent full image as base restoring it, then applying changes in itself.




No. See above.




You create differential and incremental images because they will be made faster and will be smaller than full backups.

Kari

For clarity, incrementals are not included in free version. For average user, this is no big deal as diffs are still tiny compared with base image in most cases.

cereberus said:

For clarity, incrementals are not included in free version. For average user, this is no big deal as diffs are still tiny compared with base image in most cases.

Yes. My bad, I forgot to mention that.

Post
Many thanks to Kari and Cereberos. I am now happy about Differentials. The Macrium backup setup I am using, described in Post #1, is a trial for a permanent system with the same settings except for the Full backup being made once per month, and the number of differentials increased proportionally to 16. This time of a month between Full backups is chosen on Dalcina’s advice in another post a couple of weeks ago. This was to note that my backup involved my entire D: drive which holds about 500 GB of Documents, Videos, Pictures and Music. Because only about 5% or less of this changes during a month it seems unnecessary to make the Fulls more frequently (relying on the Diffs following a crash). So much for my Macrium backup system, now set up as I want it.

I have used Free File Sync (free, donations welcome) for about 18 months for backup. It is very easy and simple to use. When the source and backup locations are chosen from a list of custom setting that you have written, FFS is started. On running FFS I choose Synchronise (Mirror). There are other setting here – Mirror makes the source and destination identical. Two blank panels open. On pressing Compare FFS fills these panels, the left with a list of all the files on the backup that require updating. This is quick even for 500 GB. Then the right panel fills with a list of files that need to be deleted (because they are not on the source) or which are new or need updating. This allows safety checking concerning the proposed deletions.

On pressing Synchronise (Mirror) (which makes the backup an identical copy of the source) this results in the backup being made up to date. This would take about the same time as a differential in Macrium would take in the same circumstances. That’s it. What FFS seems to be doing is creating what is effectively a Differential (whose changes are listed on the right panel), and then when instructed (pressing “Synchronise”) applying those changes to the backup. There is no visible Differential file.

On its first run when backing up to an empty backup disc, this takes time – about the time that Macrium takes to make its Full backups.

When comparing FFS and Macrium (as I see them):

1. The only Full backup that ever takes place or is saved to HD is on a first run of FFS – no time-consuming and disc-hogging periodic Full backups as with Macrium, and FFS requires only one Full whereas Macrium requires two in most cases. These can be very big files if the source drive is big.
2. After a crash, to restore your source disc, you only need to run FFS and change its source and backups from left to right (previously source to backup discs ) to right to left (now backup to source) and manually Synchronise FFS. With Macrium, run (double-click) the latest Diff which will automatically restore the source (an even easier task).
3. With FFS it is possible to set up an automatic schedule to run the backing up process whenever the operating system detects that a change (any size or type of change) has occurred in the source drive. This would be very simple and elegant, making a backup that is up to date to the minute. However, you need to write a command line and write a file “Batchjob.ffs_batch, and FFS gives details here but does not give sufficient info on how to write the batch file and what should go into it so I am unable to set up such a schedule. I will need to investigate further. (Can anyone help here?)
4. Macrium can also set up a schedule. This is easy and allows you to choose one specific or several specific week days (eg., every Tuesday, or every Monday and Thursday) and at what time of day; and you can set up one or more specific dates in every month at a specific time.

I prefer Macrium for backups of C: every day, and the simplicity and elegance of FFS for my D: drive provided I can learn how to set up its “Batchjob.ffs_batch” file. I will need to investigate.

Attached is a copy of a spreadsheet summarising my backup regime. Its probably over the top but I never want to lose family photos going back 150 years and other precious things.

I hope this helps people wanting to set up a backup system, which is really really important as I found last Easter.