4.2.3. Storage Parameters

The following parameters configure local storage devices for installing a Hypervisor.

`storage_init`

The storage_init parameter is required for an automated installation, it initializes a local storage device.

Presently, Hypervisors use one storage device for local installation. There are four methods for defining which disk to initialize and install on.

For USB storage devices, use the usb parameter to select the disk type. For example:
```
storage_init=usb
```
For SCSI hard drives, use the scsi to select the disk type. For example:
```
storage_init=scsi
```
For CCISS devices, use the cciss parameter to select the disk type. For example:
```
storage_init=cciss
```
Alternatively, the storage device can be specified by using the Linux device name as the storage_init parameter. Using device names in the format /dev/disk/by-id is not supported. storage_init must use the format /dev/mapper/disk or /dev/disk. In this example the /dev/sda device is specified:
```
storage_init=/dev/sda
```

When specifying a storage_init value of usb, scsi, or cciss you also have the option of appending a serial number to explicitly set which device to use. The serial number for the device is determined by running the command shown in Example 4.3, “Finding udev Serial Numbers”.

Example 4.3. Finding `udev` Serial Numbers

This command lists serial numbers for all disks attached to the system.

$ for d in /dev/sd?; do echo $d `udevadm info -q env -n $d | grep ID_SERIAL=`; done
/dev/sda ID_SERIAL=ST9500325AS_6VE867X1

When providing both a storage type and the serial number you should ensure that the two values are separated by a colon (:), for example:

storage_init=cciss:3600508b100104a3953545233304c0003

Note — Device Names are not Persistent

Consistency of devices names following a system restart is not guaranteed. Device names are liable to change.

`storage_vol`

The storage_vol parameter is used to partition the storage device set by the storage_init parameter. After storage_vol= there are six fields separated by colons. Not all fields have to be specified, those that you do not define during installation will be assigned their default value.

The first and third values represent the boot and root partitions respectively, which have fixed sizes. These values cannot be set and should be left undefined.

All values are in megabytes (MB). Do not append units onto the end of the values.

Setting a size value of -1 sets the partition to take up all remaining disk space. Note that this can only be used with the Data partition.

The following is the standard format of the storage_vol parameter with each element described in the list below.

Example 4.4. Format of the storage_vol Parameter

storage_vol=:SWAP::CONFIG:LOGGING:DATA

SWAP
The swap partition is used for swapping pages of memory which are not frequently accessed to the hard drive. This frees pages of memory in RAM that are in turn used for pages which are accessed more frequently, increasing performance. The default size of the swap partition is calculated based on the amount of RAM installed in the system and over-commit ratio (default is 0.5). Hypervisors must have a swap partition and the swap partition cannot be disabled by setting its size to 0. The minimum size for the swap partition is 8 MB.
Red Hat Knowledgebase has an article on determining the size of the swap partition.
Use the formula from the Red Hat Knowledgebase and add storage for the over-commit ratio (RAM multiplied by the over-commit ratio).
```
Recommended swap + (RAM * over-commit) = swap partition size
```
Leaving the value empty allows the system to sets the recommended value for the swap partition.
CONFIG
The config partition stores configuration files for the Hypervisor. The default and minimum size for the configuration partition is 8 MB.
LOGGING
The logging partition stores all logs for the Hypervisor. The logging partition is required and the recommended size is 2048 MB.
DATA
The data partition must be large enough to hold core files for KVM. Core files depend on the RAM size for the guests. The data partition must also be large enough to store kernel dump files, also known as kdumps. A kdump file is usually the same size the host's system RAM. The data partition also stores the Hypervisor ISO file for Hypervisor upgrades.
The data partition should be at least 1.5x as large as the RAM on the host system plus an additional 512 MB in size. The minimum size is 256 MB.
The default size for the data partition is the remaining available disk space (labeled as -1).

Example 4.5. Using the `storage_vol` Parameter to Partition Default Sizes

storage_vol=:::::

Example 4.6. Using the `storage_vol` Parameter to Partition Certain sizes

The Boot partition is always omitted, and therefore defined as the fixed size of 50 MB.

The Swap partition is defined as 4000 MB.

The Root partition is always omitted, and therefore defined as the fixed size of 512 MB.

The Config partition is defined as 8 MB.

The Logging partition is defined as 2048 MB.

The Data partition is defined to take up all remaining disk space.

storage_vol=:4000::8:2048:-1

`iscsi_name`

The iscsi_name parameter is used to set the iSCSI Initiator Name. The iSCSI Initiator name is expected to take the form of an iSCSI Qualified Name (IQN). This format is defined by RFC 3720, which is available at http://tools.ietf.org/html/rfc3720.

The IQN is made up of the following elements, separated by the . character:

the literal string iqn,
the date that the naming authority took control of the domain in yyyy-mm format,
the reversed domain name - demo.redhat.com becomes com.redhat.demo, and
optionally, a storage target name as specified by the naming authority - preceded by a colon.

Example 4.7. `iscsi_name`

The following illustrates the IQN for an iSCSI initiator attached to the demo.redhat.com domain where the domain was established in July 2011.

iscsi_name=iqn.2011-07.com.redhat.demo