How much free memory does Duplicati need to back up an external hard drive?

The external hard drive has 1.39TB memory usage. The Lenovo note book has 256GB of SSD memory but with only 3GB available, the Duplicati backup scheduled daily fails every time, due to a lack of memory.

To be clear are you trying to back up the 1.39TB external drive? (To where?) Or are you backing up the internal drive TO the external drive?

In any case, Duplicati will store the job database on your C: drive by default. This database can become quite large if you are backing up a lot of data. One way to reduce the database size is to use a larger deduplication blocksize. The default is 100KiB. I can recommend a size once you confirm how much data you’re trying to back up.

Also another thing that sometimes gives people trouble is when they change the remote volume size option. It defaults to 50MiB, which is just fine for most situations. Some people set it to something ridiculously large and it will cause problems.


Thank you for getting back to me so quickly.

I am backing up a 2TB external hard drive that currently has 1.39TB of data stored (the data I am trying to back up). To back up that hard drive to Duplicati I ensure it is connected to my laptop at the scheduled time the hard drive backup is attempted. This is something my son set up for me but he is away for two weeks and the data is not backing up and also I do not have, atm, the details to login to Duplicati. The external hard drive has failed to backup for a long time and it is time I resolved the issue.

The laptop itself is not set to back up to Duplicati, it is merely the device facilitating the backing up of the external hard drive. The laptop only has SSD (C drive) memory and which is only 256GB total, and only 3GB are unused/available.

Is this a scenario where the external hard drive can successfully backup?

I cannot check the remote volume size atm.

Thank you for your help with this,


You presumably mean free space on that SSD, right? 3 GB left is very tight even without Duplicati.

Sometimes one can temporarily free up disk space by deleting big files from Recycle Bin, clearing
browser cache (which is just a bit of a performance booster and will come back), and such things.

In Windows Settings, Storage Sense can even help delete things, such as unused temporary files.

Searching for
free up disk space “windows 10”
will find other ideas, but some might be riskier than you’d prefer, especially without current backup.

Having had a mechanical drive of that size, I can say that constant drive space fights can get tiring.
My solution was a drive upgrade which is typically possible, however I can’t speak for your system.

Is there an error message? If so, can you post? If it actually said “memory”, then maybe it’s memory.
How far does it get before whatever problem you see happens? How do you even see it without GUI?
Reports (e.g. by email) are possible, but they would have to be set up by someone with GUI access.

How to find how much hard drive space is available comments and says how to monitor drive space.

You say you don’t actually have access to either the Duplicati GUI or the backup files (very awkward), however you can at least watch your 3 GB of free space to see whether it seems like it heads to zero.
It looks like the Devices and Drives display might not auto-refresh, but you can press F5 to refresh.

If you truly have a memory problem, you can watch Task Manager in Performance tab to see whether Committed gets to limit. You can see for yourself what this unknown configuration may be exhausting.
Providing answers to questions asked (such as where and how it fails) might provide some clues too.