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October 5th, 2015 08:00
Avamar 3 day retention
I have a customer that is only saving 3 days of backups. They state that data older than 3 days has no value.
I know the suggested minimum retention is 14 days from Avamar. I know that best practices states that you want to get commonality and ensure that the backups complete before backups expire and at the very least, have a 7 day retention.
My question is how does the 3 day retention affect the system overall? It seems you would need to clean more data more often and would cause higher CPU and disk activity. Should I have them go to a 14 day retention?
I am also looking for some official EMC documentation stating these points, if it exists.
Thanks
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ionthegeek
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October 6th, 2015 06:00
Having a very short retention increases the rate of "churn" on the system -- the amount of data being added and the amount of data being garbage collected every day. A high change rate is okay if you maintain a low overall capacity. At higher capacities, higher change rates produce a lot more checkpoint overhead which consumes physical disk space because we need to change more files every day to store the same amount of data. Keep in mind that this is an exponential increase.
The next question is -- what if the system suffers an hfscheck failure on the Friday night of a holiday weekend and support determines that the only recourse is to roll back? By the time support gets on the system and completes their analysis, all of the backups from the customer's most recent validated checkpoint will be expired after the rollback completes.
I would always recommend a minimum 14 day retention for these reasons.