Disk Format

OS Disks should be set up using Logical Volumes (LVM) and care should be taken to ensure that the sectors are properly aligned.

Disk performance is possibly the single most important item for indexing and searching at scale

Format the disk using parted

In this example, we have set the disk to /dev/sda, you can view available disks using fdisk -l | grep "/dev/[v|s|nv|mapp]"

disk=/dev/sda parted -a optimal ${disk} mklabel gpt unit s mkpart primary 2048s 100% align-check opt 1 set 1 lvm p
Next, create the physical volume in LVM

pvcreate -M 2 --dataalignment 4k ${disk}
Check alignment (the first PE should be 1.00m)

pvs -o +pe_start
Create the Volume Group (this may already be on your server, so possibly optional):

volumeName="vg0" partition=1 # this is the partition you created above with parted, be sure it matches! vgcreate ${volumeName} ${disk}${partition} lvcreate -l 100%FREE ${volumeName}
Create a filesystem on the new LVM volume

rootVol=$(lvdisplay | grep Path | grep root | awk '{print $3}') # THE NEXT COMMAND WILL DESTROY DATA, BE SURE IT IS WHAT YOU WANT! mkfs.ext4 ${rootVol}
Create an fstab entry

Replace ${rootVol} below with the actual volume name for your server.

/dev/mapper/${rootVol}/ ext4 errors=remount-ro 0 1

During a new OS install, all of this is done for you when choosing the automatic option. However, be sure to select LVM as the type. LVM also allows you to add more disk and resize the root volume later without the need to reboot.

Swap

Disable it...always!

Swap was originally used to compensate for lack of Ram. Today's servers should have ample ram and, if not, will suffer severe performance degradation should the OS run low and need to swap to disk.

If you find that your server is low on memory and must add swap, then be sure to set the swappiness, but also be sure to consider this a temporary fix while you place an order for more RAM from your vendor.

We can see the current swappiness value by typing:

  cat /proc/sys/vm/swappiness
  60

For a Desktop, a swappiness setting of 60 is not a bad value. For a server, we'd want to move it closer to 0.

We can set the swappiness to a different value by using the sysctl command.

For instance, to set the swappiness to 10, type:

  sysctl vm.swappiness=10
  vm.swappiness = 10

This setting will persist until the next reboot. You can set this value automatically at restart by adding the line to /etc/sysctl.conf:

At the bottom, add vm.swappiness=10, then save and close the file when you are finished.

Next, type sysctl -p to have the OS re-read the new settings.

Another related value that may be useful is the vfs_cache_pressure. This setting configures how much the system will choose to cache inode and dentry information over other data.

This is access data about the filesystem which is generally very costly to look up and is frequently requested. So it's an excellent thing for your system to cache. You can see the current value by querying the proc filesystem again:

  cat /proc/sys/vm/vfs_cache_pressure
  100

As it is currently configured, our system removes inode information from the cache too quickly. We can set this to a more conservative setting such as 50 by typing:

  sysctl vm.vfs_cache_pressure=50
  vm.vfs_cache_pressure = 50

Again, this is only valid for our current session. We can change it by adding it to the sysctl.conf file.

  vi /etc/sysctl.conf

At the bottom, add the line that specifies your new value:

  vm.vfs_cache_pressure = 50

Save and close the file when you are finished and type sysctl -p so that the changes get read.