My system runs mostly from SSD but I have two hard drives mounted as follows:

/dev/sdb1 /Photographs ext4 rw,relatime 0 0

/dev/sdc1 /Ddrive fuseblk rw,relatime,user_id=0,group_id=0,allow_other,blksize=4096 0 0

The are both set to spin down after a period of no use.

My problem is, when I shut the system down it has to spin up sdb1, the
ext4 formatted drive before shutdown completes. I am not so worried
about the time that takes, but more concerned not to wear out the disk
doing nothing useful.

sdc1, the ntfs drive, doesn't have the same problem. I am guessing
that the ext4 system software wants to write to sdc1 that it has
shut down cleanly. Is there a way to prevent that, or even better,
avoid spinning up the drive until the first time I use it (which
is often not at all in any given day).

Thanks for any help you can give. It is debian 10 by the way.

Hi Sploog,
Spinning the disk up and down during a session is likely to wear it out quicker. If the disk is spinning, by Newton's first law of motion, it should keep spinning if possible. Most data centres (which use flying rust disks) have probably had them spinning constantly for years!
Every time it has to spin back up it has to overcome the platter's inertia (also uses more power to spin up than maintain spin speed.) and possibly a thing known as "stiction" which translates as the friction in the hub bearings and also overcoming the "disk brake" effect of the heads on the platter. Though some disks will have a landing area, while others may park the heads off the disk.

So, in a word, Let 'em spin!

My

Play Bonny!

I would guess that the ext4 drive spins up to verify the journal before it shuts down. Might have some metadata in memory that it needs to write?