So in https://infra.nue.suse.com/SelfService/Display.html?id=178140 we came to the agreement that it is easier and better to keep both vdc+vde even if both are on "cheap+slow" storage.
I have added corresponding comments in /etc/fstab now, complete file content:
devpts /dev/pts devpts mode=0620,gid=5 0 0
proc /proc proc defaults 0 0
sysfs /sys sysfs noauto 0 0
debugfs /sys/kernel/debug debugfs noauto 0 0
usbfs /proc/bus/usb usbfs noauto 0 0
tmpfs /run tmpfs noauto 0 0
# 7116dc72-ebc8-4b21-8847-b9f31dc95229 -> vda1
# ssd storage "expensive+fast"
/dev/vda1 / ext3 defaults 1 1
# 2e55520d-2b90-4100-8892-025c5f4c9949 -> vda2
/dev/vda2 swap swap defaults 0 0
# 6c8044d6-5497-4db6-9714-89b76268121e -> vdb
UUID=6c8044d6-5497-4db6-9714-89b76268121e /srv xfs defaults,logbsize=256k,noatime,nodiratime 1 2
/srv/PSQL10 /var/lib/pgsql none bind 0 0
# 3f003a69-c51e-4d79-8b83-906e7918bac4 -> vdc
# rotating disk "cheap+slow"
UUID=3f003a69-c51e-4d79-8b83-906e7918bac4 /assets xfs defaults,logbsize=256k,noatime,nodiratime 1 2
/assets /var/lib/openqa/share none bind 0 0
# 51d504aa-6f46-4b89-bcd9-b6cea7b8b755 -> vdd
# ssd storage "expensive+fast"
UUID=51d504aa-6f46-4b89-bcd9-b6cea7b8b755 /results xfs defaults,logbsize=256k,noatime,nodiratime 1 2
/results /var/lib/openqa none bind 0 0
# cf441a62-3f8c-4b29-928b-0f0161e8240b -> vde
# rotating disk "cheap+slow"
UUID=cf441a62-3f8c-4b29-928b-0f0161e8240b /space-slow xfs defaults,logbsize=256k,noatime,nodiratime 1 2
/space-slow/assets/factory/iso/fixed /assets/factory/iso/fixed none bind 0 0
/space-slow/assets/factory/hdd/fixed /assets/factory/hdd/fixed none bind 0 0
/srv/homes.img /home ext4 defaults 1 1
I asked gschlotter for more space on /space-slow as well and have extended the file system:
current df situation:
/dev/vda1 9.6G 6.3G 2.9G 69% /
/dev/vdb 80G 51G 30G 64% /srv
/dev/vdc 7.0T 3.8T 3.3T 53% /assets
/dev/vdd 5.0T 3.7T 1.4T 74% /results
/dev/vde 3.0T 1.6T 1.5T 53% /space-slow
This means that likely we will not have a problem with "assets" very soon, "results" are more likely to pose a problem.