`coldsnap download` hangs at end of download, but only for large downloads

[camtarn]

I am trying to download some large snapshots (2TB and 3TB) from EBS. They reliably hang at the end of download:

Downloading [=================================================>] 3827075/3827138 (3s)

Multiple smaller snapshots (100GB) downloaded successfully, but I have tried downloading these large snapshots multiple times and they always hang. Leaving the hung download for multiple days does not result in it completing successfully.

Unlike #353 I am not downloading multiple files into the same directory - I only have a single download running.

The download is being written onto an external SSD formatted with exFAT. I have checked dmesg/journalctl and don't see any I/O errors, and the disk is not full.

Using cat /proc/meminfo shows very few (a few kB) dirty pages awaiting being written to disk.

Coldsnap version: 0.6.2
aws CLI version: 2.22.18
Running on: SUSE Linux Enterprise Server 15 SP4 / Linux 5.14.21

[camtarn]

I managed to get this working on an EC2 instance running Ubuntu, so I suspect it's something to do with my server setup.