Our services are no longer on bare metal, instead, new services are on VPS. Recently we have a problem on CE7 when reboot and it waiting for swap partition, which we have removed completely to free-up space.
Since hypervisors will manage disk IO and memory of VPS, default i/o scheduler & memory paging will double the I/O. Hypervisor allow overcommit on memory, and it will try to take free memory from other idled VPS, before it start paging to disk. Therefore, best practice are I/O scheduler set to noop and disable memory paging by turn it off & remove swap.
CE7 auto tuned i/o schedule to noop when detect itself are running under hypervisor, but it won’t turn off swap and allocate plenty amount of disk space for swap partition.
Turn off swap is simple.
$ sudo swapoff -a
and remove it to free-up space.
$ sudo lvremove -Ay /dev/centos/swap
of course reassign it to /dev/centos/root
$ sudo lvextend -l +100%FREE centos/root
But one point we are missing, grub2.cfg need to be regenerate, but modification needed before regenerate.
$ sudo vi /etc/default/grub
##GRUB_CMDLINE_LINUX="rd.lvm.lv=centos/root rd.lvm.lv=centos/swap crashkernel=auto rhgb quiet"
GRUB_CMDLINE_LINUX="rd.lvm.lv=centos/root crashkernel=auto rhgb quiet"
$ sudo cp /etc/grub2.cfg /etc/grub2.cfg.bak
$ sudo grub2-mkconfig >/etc/grub2.cfg
Viola! No more swap partition waiting for next reboot!