I am backing up my machine on an external HDD hard-drive of 2TB formated in exFAT via USB using rsync on Ubuntu 22.04 and the file is extremely slow (sometimes stuck at 20kB/s for several seconds). How could I do to see what is the problem or speed things up?
The model of the HDD (Western Digital) is the following:
$ sudo hdparm -I /dev/sda | grep -i number
Model Number: WDC WD20SDRW-11VUUS0
It's quite possible that this is the correct behavior of this disk.
Several sources say that your disk model is Shingled magnetic recording (SMR), which means that it has a faster buffer that when full would need flushing out to the slower part. On some models with a large buffer the flushing can take a very long time. Write speed for SMR disks is optimal when the disk is wiped clean, but could become very slow if it's quite full or the data size exceeds that of the buffer.
You could wipe the disk before every backup operation to achieve maximal write speed, or you'll just need to give the disk the time it needs to complete the operation.
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