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Backup Schedule Mix Incremental and Differential

Posted: Sat Jan 02, 2010 6:04 pm
by Brettman

I have limited disk space and want to back up a few terra bytes of data, therefore I would like to implement the following backup schedule using scripts and would like to know the answers to the following questions:

1) First Saturday of each Quarter run a full backup
2) Every Saturday other than the First Saturday of each Quarter run an incremental backup
3) Every day other than saturday run a differential backup for the differences from the last incremental or full backup

I want to retain for long term keeping only the Full Backup and the Incremental backups; the differential backups I want to discard after 7 days

R-Drive Command Line

I've worked out the following command lines for my backups
1) For the full backup ->

Code: Select all

r-driveimagecl.exe create /a /o -s=C: -a="F:\Backups\C-Drive.arc" -r="C Drive Full Backup" -c=3 -u
2) For the incremental backup ->

Code: Select all

r-driveimagecl.exe append /a /o -append-inc -s=C: -a="F:\Backups\C-Drive.arc" -r="C Drive Incremental Backup" -c=3 -u
3) For the differential backup ->

Code: Select all

r-driveimagecl.exe append /a /o -s=C: -a="F:\Backups\C-Drive.arc" -r="C Drive Differential Backup" -c=3 -u

a) Can I delete the differential backups without affecting the incremental or full backups?
b) How can I tell which backup files are the differential backup files compared to the incremental files; the files just have sequential suffixes and unless I open each one to read the comment it doesn't seem to be able to be automated, there is no command line switch to use a separate output file from the input file?

Many thanks in advance for any help


Re: Backup Schedule Mix Incremental and Differential

Posted: Wed Jan 06, 2010 6:52 am
by Alt
1. Full backups are full backups. They contain all data to the moment they are created. You don't need any other files, including differential backups, to restore data from a full backup. The situation is different with incremental backups. When restoring data, you will need the full image and ALL files (both incremental and differential ones) created to the instant to which you want to restore data. So, if you delete a differential backup in your scheme, you'll lost all backups from the moment of the deleted differential backup to the next full or differential backup.
2. No, all types of partial backups have the same name convention for R-Drive Image to be able to understand which files belongs to which backup set.

Re: Backup Schedule Mix Incremental and Differential

Posted: Sat Jan 09, 2010 10:09 pm
by Brettman
Thanks for the response.

However exploring this a little more...lets assume I run a full backup and then only daily differential backups using the -bs options, e.g. -bs -bs-num-b="4" -bs-num-f="90", i.e. full backup every 91 days with daily differential backups in between the full backups.

Assuming at day 40 I want to reduce disk space and delete the differential files from day #2 to day #39 where day #1 is the full backup and day #2 onwards are the differential backups, hence I'm left with the full backup from day #1 and the most recent differential backup from day #40;

1. Do I have enough files for a complete restorable image to day #40 or do the intermediate differential backup files contain data that I will loose when I restore at day #40 with my full backup and only day #40 differential backup
2. Will the -bs options continue with the next differential backup on day #41 or will it loose this and start at #2 again?

I could spend hours trying to work this out myself through trial and error but I guess someone somewhere must have tried this and found it either worked or failed.

I've a large full disk images but very small (about 0.5% of the full) differenial images and would rather keep as long a backup cycle if possible, perhaps even half yearly.

Many thanks in advance again.

Re: Backup Schedule Mix Incremental and Differential

Posted: Mon Jan 11, 2010 11:03 am
by Alt
1. As you use _differential_ backups, you need to have a full backup file and one differential backup file to restore data to the moment the differential backup was made. Therefore, for your case, the full backup file made on day #1 and the differential backup file #40 are enough to restore data to the moment differential backup #40 was made.
What you loose is that you cannot restore data to the moments #2, #3,...#39.
2. The backup process will continue on day #41.

Re: Backup Schedule Mix Incremental and Differential

Posted: Tue Jan 12, 2010 7:43 pm
by Brettman
Thanks again for your reply

However I'd set up a test as I just wanted to be sure, using the same scenario described above, I ran the differential backup with the -bs options as descried above and in the manual using the number of backup sets at "4" and the file per backup set at "90"

For point 1
I found that when the number of files reach 91 or greater a new full backup was not created and the subsequent backups were suffixed with 92, 93, 94, ect.. ; Eventhough I did all the testing on a single day I would have expected the next full backup to occur as the number of files was exceeded.

Please confirm how use backup sets as per the documentation because my tests did not show it working as per the documentation.

For point 2
I found that if I delete the differential backups from day #2 to day #39 then on day #41 the differential backup file name will have the suffix 2, e.g. TestBackup_20100112_135119_2.arc, instead of 41 which is what I would have hoped for, e.g. hoped it would have been: TestBackup_20100112_135119_41.arc

This now can become confusing as to which is the newest differential backup, as the suffix no longer contains that information if I delete intermediate differential backups and am now totally reliant on the backup file date and could be in a situation with mutiple files of the same name with different backup dates.

This does not seem to agree with your response, i.e. yes day #41 the backup continues however the file is suffixed with 2 not 41. I would suggest this seem to me to be a bug.

Many thanks again for any help

Re: Backup Schedule Mix Incremental and Differential

Posted: Wed Jan 13, 2010 5:27 am
by Alt
1. R-Drive Image deletes backups sets rather than individual files and always keeps at least one backup set. A new backup set starts when a new full backup image is created according to your schedule for full backup images. So, even if the number of files, their total size, etc., exceed the numbers specified in Backup sets parameters but there is only one backup set present, R-Drive Image keeps the files of that backup set and continues it until it's time to create a new backup set. So, check that the number of files to be kept is in consistence with your schedule for the full backup images.
2. This is not a bug. R-Drive Image adds 1 to the number of the last differential backup image file for the sake of its internal numbering consistency. If you delete some, R-Drive Image will continue from the last+1 number. Please note that it also appends date stamps to the file names to use them as references. You can't have the same file names as at least their date/creation time will be different.