Skip to the content

Topics Covered

NOT EXECUTED Create and mount The security group rule everyone forgets What EFS is actually for Cost, which is the reason to think twice Azure and GCP
On this page
  1. NOT EXECUTED
  2. Create and mount
  3. The security group rule everyone forgets
  4. What EFS is actually for
  5. Cost, which is the reason to think twice
  6. Azure and GCP

NOT EXECUTED

This repository has no cloud account, and none will be created. Creating one requires a payment card and accepts a billing relationship, which is not something a study repository should do on anyone's behalf.

So this file is what you type, with the traps marked. It has never been run here, and nothing in the notes claims an output for it.

The runnable half is 04_storage.py, which prices EFS against EBS and S3 on the same terabyte.

Create and mount

aws efs create-file-system --performance-mode generalPurpose \
    --throughput-mode elastic --tags Key=Name,Value=shared-data
aws efs create-mount-target --file-system-id fs-xxxx \
    --subnet-id subnet-xxxx --security-groups sg-xxxx

On each instance:

sudo apt install -y amazon-efs-utils
sudo mkdir /shared
sudo mount -t efs -o tls fs-xxxx:/ /shared
echo 'fs-xxxx:/ /shared efs _netdev,tls 0 0' | sudo tee -a /etc/fstab

_netdev is not optional. It tells systemd to wait for the network before mounting. Without it the mount fails at boot, every time.

The security group rule everyone forgets

The EFS mount target needs an inbound rule allowing NFS (TCP 2049) from the instances' security group. Without it the mount hangs — it does not fail with a useful message, it hangs — and this is the single most common EFS problem.

What EFS is actually for

Mount it on many instances at once, and they all see the same files with POSIX semantics — locking, permissions, in-place writes. That is the whole feature, and nothing else in the storage lineup offers it.

Use it for Do not use it for
a shared home directory across a fleet a dataset one batch job reads once
shared model artefacts several workers read a database's data files
a lift-and-shift app that expects a filesystem anything a pipeline can read from S3

Cost, which is the reason to think twice

EFS Standard is about $0.30/GB-month — roughly 13x S3 Standard and nearly 4x EBS gp3. Use EFS Infrequent Access with a lifecycle policy (--lifecycle-policy TransitionToIA=AFTER_30_DAYS) and the cold portion drops by about 90%.

"We put the training data on EFS because it was easy to mount" is how a storage bill triples. That data belongs in S3.

Azure and GCP

AWS Azure GCP
Managed NFS EFS Azure Files (NFS/SMB) Filestore
Protocol NFSv4.1 SMB and NFS NFSv3

Azure Files speaks SMB, which matters if your workload is Windows — that is the one real difference between the three.

← Back to the lab ← Course home