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Available memory requirement for successful Avamar backup?
How much memory needs to be available on the target server for Avamar backup to succeed? The target server has 32GB of RAM and its f_cache2.dat file is 13GB. I was thinking that the server would need 13GB of memory free in order to load the file into memory, but this seems like an awful lot of memory. I did a little research and found mention that because Avamar is a 32-bit application that the maximum memory it needs is 2GB (Look for blog post "Despite the Hype: Avamar client files F_cache.dat and P_cache.dat").
Avamar backups are successful until the RAM usage reaches around 80%. Then we reboot the server and Avamar backups start working again for three weeks or so, presumably because the RAM usage has decreased.
We are thinking of adding more RAM to the server so I'm trying to figure out how much memory Avamar needs.
ionthegeek
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June 25th, 2021 09:00
The f_cache2.dat file is what's called the "paging" cache. The two main advantages of the paging cache are that it can be used for DD integrated backups and that it only loads a limited number of pages into memory at one time.
Memory usage for the paging cache shouldn't be more than a few GB at most. It shouldn't reach 13GB.
Note that the blog post you referenced is from 2013 and a LOT has changed since then.
Based on the symptoms you've described, it sounds like there may be an application on this system that has a memory leak (and I won't rule out Avamar). If you track memory usage over time, is there one particular application where the memory usage grows consistently?
Tim Diskataneous
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June 25th, 2021 12:00
Thanks for getting back to me ionthegeek!
You asked, "Based on the symptoms you've described, it sounds like there may be an application on this system that has a memory leak (and I won't rule out Avamar). If you track memory usage over time, is there one particular application where the memory usage grows consistently?". The person in charge of the server and application says, "The interface engine is like MS Sql Server in that I can define how much memory to allocate for the engine to run and it will use 100% of it, needed or not. Current total is about 28gb of ram for HealthShare. The more memory for HealthShare the faster it runs. So we allocated the majority for it, but left a decent amount for OS and other random items that may run on the server. ".
We are thinking about adding RAM to the server or changing the amount of RAM that is given to the application. We need to know how much memory Avamar needs to successfully backup the server so we can make a plan. Here is what I told them. Let me know what I got right and what I got wrong
"Avamar only needs 2GB of memory to run successfully, but it won’t take the last 2GB and leave nothing for the server."
"So for Avamar to run a successful backup of , which has quite a bit of data, there needs to be between 7GB to 12GB of available memory so that Avamar can take 2GB and leave 5GB-10GB for the server."
"I’m still researching, but 7GB-12GB of free memory is reasonable I think."
"The memory requirement is different for each server and is based on how much data is being backed up and the size of two Avamar .dat files that must be loaded into memory."
"One of the .dat files is used by Avamar to identify which files have already been backed up. The other .dat file has a similar function except that it is related to chunks and composites that have already been backed up."
Thanks for your help!