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dcloud
Starting Member
USA
6 Posts |
 Posted - July 13 2014 : 18:10:33
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| I have 2 external hard drives. I will do a full backup on one and the next full backup on the other. Then I alternate the incremental backups the same way. This way, in case of mechanical failure of the external drive, I might just lose a day's worth of work. I might have 4 full backups and 20 incrementals on each drive. My question - FINALLY - is there an advantage of full over incremental? Could I just make one full backup and 200 incrementals? I can fit a lot of 4GB incrementals on a drive versus 325GB fulls. Is one way 'safer' than the other for recovery? Thank you for your input. |
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Seekforever
Advanced Member
Canada
640 Posts |
Posted - July 13 2014 : 18:34:08
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The major issue with a long string of incrementals is that if any one breaks then all the others past that point are useless. You might consider no more than a dozen incrementals or if you are like many, a Full every week and then an incremental for the remainder of the week. There is really no absolute answer. Since you have 2 externals you are in much better shape than the single external user.
It is indeed possible for a backup to go bad on a HD even though it was correctly written and verified. The disk can develop bad clusters perhaps due to a head crash. I had this happen to me - I had to go back more than a couple of Fulls before I found a good one. This is also indicative of another thing to do, let the backups build until you need the space; there is really no benefit in deleting old ones until then even if it does make you feel like a good housekeeper.
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Edited by - Seekforever on July 13 2014 18:36:44 |
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dcloud
Starting Member
USA
6 Posts |
Posted - August 10 2014 : 19:20:42
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quote:
Originally posted by Seekforever
The major issue with a long string of incrementals is that if any one breaks then all the others past that point are useless. You might consider no more than a dozen incrementals or if you are like many, a Full every week and then an incremental for the remainder of the week. There is really no absolute answer. Since you have 2 externals you are in much better shape than the single external user.
It is indeed possible for a backup to go bad on a HD even though it was correctly written and verified. The disk can develop bad clusters perhaps due to a head crash. I had this happen to me - I had to go back more than a couple of Fulls before I found a good one. This is also indicative of another thing to do, let the backups build until you need the space; there is really no benefit in deleting old ones until then even if it does make you feel like a good housekeeper.
I should have responded sooner. Thank you for your input. It hadn't occurred to me that if the first backup is bad the next 1-1000 would be useless. I guess I've been doing it right by mistake. |
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HadleyHope
Starting Member
United Kingdom
2 Posts |
Posted - August 27 2014 : 11:08:55
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Not sure if this is correct, but from reading the info about backup sets http://kb.macrium.com/KnowledgebaseArticle50167.aspx I am planning on the following scehduling:
Every Quarter - Full backup
Every Month - Differential (should diff the last full backup)
Every Week - Incremental (should incremental the last differential?) |
Edited by - HadleyHope on August 27 2014 11:09:57 |
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Merlin
Advanced Member
852 Posts |
Posted - August 27 2014 : 13:01:48
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There really is no "correct" schedule.
It depends on your needs.
Personally, I do a full image weekly, and a few incrementals during the week.
I keep the last 4 weeks worth before purging. |
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Drac144
Advanced Member
USA
647 Posts |
Posted - August 27 2014 : 20:12:10
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I do not think there is any connection between incremental and differential files. When you do a differential backup it is done against the last full backup. So EACH differential file relates back to the full backup and is NOT connected to any other differential file. So any single differential file and the full backup are enough restore to the state as of that differential file's date.
On the other hand, an incremental is related to the previous incremental file and to the full backup. So each incremental file depends on all previous incremental files as well as the full backup. The incremental files do not relate to differential files.
So your backup strategy is flawed. Not sure why you only want a full backup each quarter unless you have a huge amount of data. If your data changes a lot, incremental backups are best to keep size down. But be careful not to have too many incrementals because if any one is bad/corrupted all subsequent incrementals are useless.
Since differentials do not depend on other differentials - just the full backup - they do not have that issue - but they DO take up much more space (if files are added/changed frequently).
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Seekforever
Advanced Member
Canada
640 Posts |
Posted - August 27 2014 : 22:28:47
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I believe Drac144 has it correct - incrementals don't get attached to differentials and if they were it could be disaster. Since only a full and the last differential are required to restore to the most recent time, users often delete old differentials which would destroy the incremental chain.
There is lots of thought going into full/differential/incremental methods but remember having them only on a single backup device is setting yourself up with a common point of failure. |
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HadleyHope
Starting Member
United Kingdom
2 Posts |
Posted - August 28 2014 : 07:48:52
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quote:
Originally posted by Seekforever
I believe Drac144 has it correct - incrementals don't get attached to differentials and if they were it could be disaster. Since only a full and the last differential are required to restore to the most recent time, users often delete old differentials which would destroy the incremental chain.
Thanks for the clarification, I had set a full for every quarter as it takes over 3 hours for the full backup, and on most machines the data does not change that much, and any important data is stored on OneDrive or can be re-downloaded from the likes of Amazon/iTunes etc so a differential for the inbetween months is fine. |
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