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Elastic Volume Service (EVS)

EVS is flexible disk provisioning for Elastic Cloud Server (EVS). Use this for production deployments where needed, so that the disk space can flexibly expanded. This prevents the need for compute migrations that cause more overhead.

EVS Setup

  1. Go to the EVS portal
  2. "Create disk"
  3. Choose the region of your destination server (for optimal performance)
  4. Choose "General Purpose SSD"
  5. Choose somewhere between 10-25GB
  6. Encrypt the volume according to the threat model (if unknown, evs/default)
  7. Optional: Add informative tags (for example, libscie=sso)
  8. Give an informative name (for example, org.libscie.git for the service on https://git.libscie.org)

We recommend using one EVS per production service, to allow for compartmentalization of disks per service. Services may be on the same server at this time, but that is not a guarantee it will remain so.

Note that disk space can be expanded at any time in the future, so if you are unsure about your needs, pick 25GB to start.

Attaching EVS to ECS

Upon creation of your EVS, it will need to be attached to be useful.useful (see also OTC docs). If you created an EVS during the server creation, it will already be attached!

Conceptually, you will partition, format, and attach the disk.

Partitioning

  1. SSH into the server
  2. Run fdisk -l or lsblk to identify the newly attached drive
  3. Run fdisk /dev/vdb (double check the drive with results from step 2) to start formatting the disk
  4. Return n to initialize the formatting
  5. Return p to setup one primary partition
  6. Take the default values for the next three steps (that is, press Enter three times)
  7. Optional: Check the partitions by returning p
  8. Return w to write partitions to disk

Formatting

  1. Run partprobe
  2. Run mkfs -t ext4 /dev/vdb1 (double check the ext4 and /dev/vdb1 for your scenario)

Attaching (aka "mounting")

  1. Identify the path where you want the disk to be attached (for example, /mnt/evs-disk)
  2. Run mount /dev/vdb1 /mnt/evs-disk (replacing the disk and attachment path)

This attaches the drive until the server is rebooted.

Attaching the disk upon boot
  1. Find the UUID for the disk blkid /dev/vdb1
/dev/vdb1: UUID="905943cb-c59b-401d-b686-22e0c1131869" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="fae0084f-01"
  1. Open the config file: nano /etc/fstab
  2. Add a new line with the specific mount information, for example
UUID=905943cb-c59b-401d-b686-22e0c1131869  /mnt/evs-disk  ext4  defaults  0 2
  1. Unattach the manually attached drive: umount /dev/vdb1
  2. Reload the fstab config - run systemctl daemon-reload
  3. Check your disk is attached

Expanding existing EVS

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