'hpsa' - A SCSI-based Linux device driver for HP Smart Array Controllers

For example:

You install RHEL 6 on a server with P400 and P212 controllers.

P400 controller uses the cciss driver on RHEL 6, according to Table 1.

P212 controller uses the hpsa driver, according to Table 1.

Any logical disks on the P212 will switch to hpsa-style naming as described in “Device naming and numbering” after

hpsa activation. The /dev/cciss/c[0-9]d[0-9] names for P212 logical disks will change to /dev/sd* names.

Transitions due to controller replacement

Since hpsa is associated with particular controllers, replacing a Smart Array controller with a different model could

result in a change of logical disk-device names. The new controller may force the use of a different device driver.

For example:

You install RHEL 6 on a server with a P800 controller using the cciss driver.

You replace the P800 controller with a P812 controller.

P812 controller will use the hpsa driver, as noted in Table 1.

Any logical disks on the P812 will switch to hpsa-style naming as described in Device naming and numbering after

hpsa activation.

Similarly, if you replace a controller using the hpsa driver with a model that only supports the cciss driver, the device

names will switch from /dev/sd* naming to /dev/cciss/c[0-9]d[0-9] names.

Transitions between pre- and post-boot environments

Pre-boot environments may detect Smart Array devices with the cciss driver and use this information to establish

configuration files for installation. This could cause a problem if the post-install environment uses the hpsa driver

instead of cciss for the installed controller.

For example, some automated installation utilties boot a temporary Linux environment on the server to be installed.

Then they perform device discovery to build configuration files for the OS install. If the device discovery environment

uses the cciss driver, the configuration files will contain cciss device names that become invalid during the OS install,

resulting in “device not found” errors if the OS uses the hpsa driver.

You must update these types of pre-boot environments and dynamic discovery tools to use the hpsa driver on certain

controllers. Likewise, scripts or utilities that assume all Smart Array controllers will have /dev/cciss/... device

names need updates to account for hpsa.

Persistent device naming

The persistent device naming method reduces the potential for problems that could occur when you change from the

cciss driver to the hpsa driver:

Unique identifiers on the logical volumes or partitions serve as the basis for persistent device names. The system either

generates the persistent device names automatically, or in the case of “by-label”, the user assigns them. The identifiers

are as follows:

 by-label—Allows the administrator to assign a meaningful name to each volume.

 by-uuid—The file system generates a unique identifier as the name.

 by-id—The storage system generates a unique identifier when the logical disk is created. The name includes the

driver type (scsi or cciss).

Instead of using actual device node names like /dev/cciss/c0d0 or /dev/sda, persistent names are used in

configuration files to avoid the problems that can arise if the device node name changes.