file system

It seems you had a bad experience with ext4, but as you can see here most linux distributions trust the ext4 file system.

So for the long-term stability and support, this is probably the best file sytem.

btrfs is less mature, but has some really interesting features for backups (snapshot and diff between snapshots). btrfs even has support for transparent comression.

It is probably a good idea to always unmount before removing the USB stick.

Wear

Flash wear is due to the limited number of erase cycle that can be done on a flash sector. Erasing a sector is necessary when data is written. If you plan to update your backup once a week, I would not be particularly worried by the flash wear.

You can reduce the flash wear by:

• Not writing access time to the file system (noatime) mount option
• Using an utility to write only what has changed (rsync).

rsync and noatime will also greatly speed-up the backup.

I also recommend to physically eject the drive when it is not mounted since I have seen some USB memory stick getting very warm even if unused.

caches and compression

I don't really understand what do you mean by caches... Now about (transparent-) compression, it will probably increase the wear because even a small change can change the complete archive.

Windows 10

ext2fsd can be used to mount an ext4 partition on Windows, and WinBtrfs for btrfs partitions.

file system

It seems you had a bad experience with ext4, but as you can see here most linux distributions trust the ext4 file system.

So for the long-term stability and support, this is probably the best file sytem.

btrfs is less mature, but has some really interesting features for backups (snapshot and diff between snapshots). btrfs even has support for transparent compression. When the source and destination are both btrfs, you can easily do incremental backups on btrfs, some interesting reading here : incremental backups on btrfs.

It is probably a good idea to always unmount before removing the USB stick.

Wear

Flash wear is due to the limited number of erase cycle that can be done on a flash sector. Erasing a sector is necessary when data is written. If you plan to update your backup once a week, I would not be particularly worried by the flash wear.

You can reduce the flash wear by:

• Not writing access time to the file system (noatime) mount option
• Using an utility to write only what has changed (rsync).

rsync and noatime will also greatly speed-up the backup.

I also recommend to physically eject the drive when it is not mounted since I have seen some USB memory stick getting very warm even if unused.

caches and compression

Your question about (write-)caching is probably because Windows does not enable write caching by default on removable media, but Linux does. The cache for reading is always enable (execpt when you use the O_DIRECT flag with the open function). Caching is probably not a so important feature is you plug the disk only for reading/writing the backup.

Now about (transparent-) compression, it will probably increase the wear because even a small change can change the complete archive.

Windows 10

ext2fsd can be used to mount an ext4 partition on Windows, and WinBtrfs for btrfs partitions.

Conclusions

Choose a file system that you're comfortable with. If the idea of snapshot and btrfs send | btrfs receive seems to obscure, go for the good old rsync over ext4.

The really important part in a backup solution is that you do it and test it regularly.