Why do i have so many ramdisks - rpi2?

[RusI]

I have Arch Linux running on my Raspberry Pi 2.
Right after install, i ran `lsblk`, `fdisk` and `df` commands (unfortunately i did not save the output) but i had one disk, which is SD card and two partitions on it. Then, i upgraded the system with `pacman -Syu`, installed `sudo` and configured `ssh`. Now, when i run fdisk it shows i have 16 ramdisks in memory with parameters:

$this->bbcode_second_pass_code('', '
Disk /dev/ram15: 4 MiB, 4194304 bytes, 8192 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes')

and all kinds of file systems mounted at various mount points:

$this->bbcode_second_pass_code('', '
Filesystem Size Used Avail Use% Mounted on
/dev/root 1.8G 1.1G 557M 67% /
devtmpfs 458M 0 458M 0% /dev
tmpfs 462M 0 462M 0% /dev/shm
tmpfs 462M 328K 462M 1% /run
tmpfs 462M 0 462M 0% /sys/fs/cgroup
tmpfs 462M 0 462M 0% /tmp
/dev/mmcblk0p1 100M 18M 83M 18% /boot
tmpfs 93M 0 93M 0% /run/user/1000')


So my questions is what are all these ramdisks and why they are in my system, since i definitely did not create them and what are those file systems mounted?

[graysky]

Normal; created by systemd. They aren't using that memory if that is your concern. That much has been allotted for their use.

[andiling]

They are optimiziations considering the fact that alarm runs from a sd card. It reduces read/write cycles to your card and enhances the life of the same.

[WarheadsSE]

Nope andiling, they are just the defaults of systemd.