One way to get a fast disk cache on an EC2 instance is to attach the local instance stores. You can use a RAID-0 setup to use multiple instance stores as a single large disk cache. This article describes the steps to RAID multiple EC2 instance stores for disk cache. If your EC2 instance only has one instance store, please see this guide.
What you need: an EC2 instance with the instance stores added (see how to add instance store to your EC2 instance)
SSH into your EC2 instance.
lsblk to view the block devices attached to the instance.
The example above shows two instance store block devices
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
xvda 202:0 0 8G 0 disk
|-xvda1 202:1 0 8G 0 part /
xvdb 202:16 0 37.5G 0 disk /media/ephemeral0
xvdc 202:32 0 37.5G 0 disk
xvdc are attached, and
xvdb is already mounted on
If the instance store volume is already mounted, please umount it.
$ sudo umount /media/ephemeral0
Set up the two instance stores as a RAID-0.
To RAID more than two instance stores, you can use the following command:
$ sudo mdadm --create --verbose /dev/md0 --level=0 --name=MY_RAID --chunk=64 --raid-devices=2 /dev/xvdb /dev/xvdc
$ sudo mkfs.ext4 -L MY_RAID /dev/md0
$ sudo mdadm --create --verbose /dev/md0 --level=0 --name=<raid name> --chunk=64 --raid-devices=<NUM DEVICES> <dev name> <dev2 name> ... <dev N name>
Create the disk cache directory for ObjectiveFS
/var/cache/objectivefs and mount the instance store.
$ sudo mkdir /var/cache/objectivefs
$ sudo mount /dev/md0 /var/cache/objectivefs
df -h and verify that the instance store directory is mounted correctly.
$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/xvda1 7.8G 1.2G 6.6G 15% /
devtmpfs 7.4G 72K 7.4G 1% /dev
tmpfs 7.4G 0 7.4G 0% /dev/shm
/dev/md0 74G 52M 70G 1% /var/cache/objectivefs
Your disk cache directory on the local instance store is now ready. See Disk Cache User Guide for configuration details. Please also remember to configure the disk cache to mount on boot.
by ObjectiveFS staff, February 21, 2016
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