Docker Images on SSD or HDD

Hello,

my server has a hardware raid 10 from HDDs as the root hard disk. Thus, the default directory of the images is also under /var/lib/docker on the HDD. I always create the required volumes for my containers on a ZFS raidz with SAS SSDs.
Does it make sense to put the images directory on the SSDs or are the image files only read when the container is created/started?

I am not sure how the containers are handled with the zfs storage driver, so I can only speak for the Overlay2 storage driver.

In Overlay2, the container filesystem is a virtual filesystem that is composed of all images layers and a copy-on-write-layer that allows write operations. Doesn’t it kind of depend on the application how much data is accessed from the container’s filesystem.

I don’t even remember If I ever ran the docker root dir from an hdd (/var/lib/docker). I always used a ssd, first with SATA interface and since a couple of years with NVME interface.

Update: it seems zfs is quite similar when it commes on how the container’s filesystem is composed (see: Use the ZFS storage driver | Docker Documentation for details), but offers additional features compared to Overlay2