Do /hash and /usemd must be used for full backups only?

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Do /hash and /usemd must be used for full backups only?

Postby Fabvit » Fri Nov 30, 2018 1:49 am

Since I understand that using /hash and /usemd params may expose future restore to risk, when used improperly, I have read very careful the IFW manual. Still I am having big problem understanding the implications of using /hash and /usemd params.

Say I perform an initial _FULL_ backup of an entire disk using /hash /usemd on the command line. (Please note I am on Windows 7/10 *with* VSS)

Now, if I later want to perform subsequent _DIFFERENTIAL_ backups, must I include both /hash /usemd on the command line for the differential backups too? Or, for differential backups, I have to omit one or both of them?

I wil like to use *only* DIFFERENTIAL type of backups since, as stated on the IFW manual "Incremental backups are hard to properly manage and tend to be troublesome during disaster recovery."

Last, I need another clarification. In the IFW manual are explained the differencies between DIFFERENTIAL and INCREMENTAL backup types.

But I was not able to argue *how* can I specifically instruct IFW to perform a DIFFERENTIAL _OR_ INCREMENTAL backup. How does IFW infers the backup type it has to perform. Maybe two simple examples (DIFFERENTIAL and INCREMENTAL) may help me understand this topic.

My biggest fear is to setup a backup strategy and later discover that I cannot recover my data!

I suggest that section "Appendix B: Backup Strategies" is complemented with relative examples of the needed command line parameters to perform DIFFERENTIAL and INCREMENTAL backup types.
Fabvit
 
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Re: Do /hash and /usemd must be used for full backups only?

Postby TeraByte Support(PP) » Fri Nov 30, 2018 10:09 am

You would use the /hash and /usemd parameters on each backup (both full and incrementals/differentials). Otherwise, you will not see the faster backup times for the incrementals/differentials.

The only difference between creating an incremental backup and a differential backup is what the base image is (basically, the type of chain). The very first backup you create that's based on the full image is exactly the same for both types. From that point, further differentials would be based on the same full image while further incrementals would be based on the last incremental.

full image.tbi
differential 1.tbi (based on full)
differential 2.tbi (based on full)
differential 3.tbi (based on full)

full image.tbi
incremental 1.tbi (based on full)
incremental 2.tbi (based on incremental 1.tbi)
incremental 3.tbi (based on incremental 2.tbi)
Paul Purviance
TeraByte Support
TeraByte Support(PP)
 
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Re: Do /hash and /usemd must be used for full backups only?

Postby Fabvit » Sat Dec 01, 2018 12:11 am

Thank you: now things are much clearer.
The only remaining question is: how can be specified the base image to use?
Fabvit
 
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Joined: Wed Jan 16, 2013 6:38 am

Re: Do /hash and /usemd must be used for full backups only?

Postby Bob Coleman » Sat Dec 01, 2018 1:37 pm

Fabvit wrote:
> Thank you: now things are much clearer.
> The only remaining question is: how can be specified the base image to use?

If using the IFW GUI, Select "Backup", then "Changes Only". The next screen will be to "Select where the existing backup file is located:".

If using a command line include "/base:" followed by the identification of the base file.
Bob Coleman
 
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Re: Do /hash and /usemd must be used for full backups only?

Postby Fabvit » Sun Dec 02, 2018 1:07 pm

Thank you so much
Fabvit
 
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Joined: Wed Jan 16, 2013 6:38 am


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