Calculating required destination size for different backup schemes
I bought the Acronis Initial Setup, which was very useful. However, when the technician set up the backups he used some arcane method of determining how much space was needed for each backup.
I don't understand how he calculated that Drive C(233 GB) could fit 2 version chains with 5 incremental versions on one drive, and then Drive D(1.8 TB) would only allow 1 version chain with 3 incremental versions.
I realize that the difference in drive size, as well as the different backup destinations are WHY that difference is needed, what I want to know is HOW he determined the schemes.
In other words, I want to know how to calculate X version chains + Y incremental versions for a given source and destination. Is there a formula, or is it just the technician's experience that gave this answer?
Thanks,
Tiggy626
Elizabeth, welcome to these User Forums.
Answering in reverse order - only the forum moderator can actually delete a forum post - the poster can edit their own comments, so can remove all text if needed but an empty post will remain.
With regards to calculating destination sizes, then this will depend on a number of factors which are difficult to guess without knowing your computer system in a lot more detail.
In essence, when doing a disk backup, then the best guide would be the size achieved when you do a full backup of that disk. This will give you an initial figure to work with that includes the effect of any Exclusions being applied and also the level of compression level achieved.
After this, the size of any Incremental or Differential backups created will really depend on the level of activity happening on the computer system. Again, running a series of such backups will give a better indication of what size you may be seeing for these.
Note: Incremental backups will normally be smaller than Differential ones.
An Incremental backup only includes the changed data since the previous backup was made (Full or prior incremental), so it is vital that any incremental backup chain remains unbroken.
A Differential backup includes all changed data since the initial full backup so will grow progressively larger over time, but have the benefit that only the full backup plus one differential file is needed for recovery versus the complete chain of full plus all related incremental backup files.
When it comes to calculating how many backups can fit on a destination drive, then it needs to be understood that Acronis automatic cleanup will only delete older backup version chains after a new full backup for the next version chain has been created successfully.
Example: Destination drive is 3TB in size.
Full backup size = 500GB
Incremental size = 50GB (approx).
Size of version chain = 1 x Full plus 10 Incrementals = 500GB + 500GB = 1TB
The maximum fit on the destination drive would be 3 version chains, i.e. 3TB (assuming that the drive actually has 3TB of available free space) but this would require that your automatic cleanup rules were set to 'Store no more than 2 recent version chains' or else you would see error messages advising that the destination drive is out of space.
So the reality is that you would put 2 x Full backups = 1TB plus 20 Incrementals = 1TB plus then a further Full backup of 500GB making 2.5TB before Acronis cleaned up and deleted your oldest version chain and freed up 1TB of data, leaving 1.5TB of used and free space on the drive.