Instance Storage

From Amazon Elastic Compute Cloud: 2009-04-04

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Instance Storage

Every instance includes a fixed amount of storage space on which you can store data. Within this document, it is referred to as the "instance store" as it is not designed to be a permanent storage solution.

If an instance reboots (intentionally or unintentionally), the data on the instance store will survive. If the underlying drive fails or the instance is terminated, the data will be lost.

We highly recommend backing up important data to Amazon S3.

Making Instance Stores Available

Inside the instance, instance stores are exposed as normal block devices and can be formatted as any file system and mounted.

Making Instance Stores Available in Linux and UNIX

Depending on the instance type, some instance stores are not mounted or formatted. To mount and format an instance store, use the Linux and UNIX mount and mkfs commands.

For added security and safety, we recommend using an encrypted file system.

Making Instance Stores Available in Windows

To initialize a volume

Log in to your instance using Remote Desktop.
On the taskbar, click Start, and then click Run.
Type diskmgmt.msc and click OK. The Disk Management utility opens.

Right-click the Amazon EBS volume, select Initialize, and follow the on-screen prompts.

	Note
	If the Initialize option does not appear, select Format.

Disk Performance Optimization

Due to how Amazon EC2 virtualizes disks, the first write to any location on an instance's drives performs slower than subsequent writes. For most applications, amortizing this cost over the lifetime of the instance is acceptable. However, if you require high disk performance, we recommend initializing drives by writing once to every drive location before production use.

To initialize the stores, use the following commands on the m1.large, m1.xlarge, and c1.xlarge instance types:

dd if=/dev/zero of=/dev/sdb bs=1M
dd if=/dev/zero of=/dev/sdc bs=1M
dd if=/dev/zero of=/dev/sdd bs=1M	(m1.xlarge only)
dd if=/dev/zero of=/dev/sde bs=1M	(m1.xlarge only)

To perform the initialization on all drives at the same time, use the following command:

dd if=/dev/zero bs=1M|tee /dev/sdb|tee /dev/sdc|tee /dev/sde > /dev/sdd

Note

Make sure to unmount the drive before performing this command..

Initialization can take a long time (about 8 hours for an extra large instance).

RAID Configuration

Configuring drives for RAID initializes them by writing to every drive location. When configuring software-based RAID, make sure to change the minimum reconstruction speed:

echo $((30*1024)) > /proc/sys/dev/raid/speed_limit_min

	Note
	You cannot use iostat (part of the sar System Activity Reporting package) to watch performance. You also cannot watch 'cat /proc/mdstat'.

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