RAID-1 and RAID-0 Volume Requirements and Guidelines

When you are working with RAID-1 volumes (mirrors) and RAID-0 volumes (single-slice concatenations), consider the following guidelines.

Custom JumpStart and Solaris Live Upgrade Guidelines

The custom JumpStart installation method and Solaris Live Upgrade support a subset of the features that are available in the Solaris Volume Manager software. When you create mirrored file systems with these installation programs, consider the following guidelines.

Installation Program	Supported Feature	Unsupported Feature
Custom JumpStart and Solaris Live Upgrade	Supports RAID-0 and RAID-1 volumes, but does not support other Solaris Volume Manager components, such as RAID-5 volumes. RAID-0 volume is supported, but only as a single-slice concatenation.	In Solaris Volume manager a RAID-0 volume can refer to disk stripes or disk concatenations. You cannot create RAID-0 stripe volumes during the installation or upgrade.
Custom JumpStart	Supports the creation of RAID-1 volumes during an initial installation only. You can create up to two RAID-0 volumes (submirrors) for each RAID-1 volume. Two submirrors usually provide sufficient data redundancy for most applications, and the disk drive costs are less expensive.	Does not support an upgrade when RAID-1 volumes are configured. More than two RAID-0 volumes are not supported.
Solaris Live Upgrade	You can create up to three RAID-0 volumes (submirrors) for each RAID-1 volume. Three submirrors enable you to take a submirror offline and perform a backup while maintaining the two remaining submirrors for continued data redundancy. Supports the creation of RAID-1 volumes during an upgrade. For examples, see To Create a Boot Environment With RAID-1 Volumes (Mirrors) in Solaris Express Installation Guide: Solaris Live Upgrade and Upgrade Planning.	More than three RAID-0 volumes are not supported.
Creating and Installing a Solaris Flash with RAID-1 volumes	You can create a Solaris Flash archive created from a master system that has Solaris Volume Manager RAID-1 volumes configured. The Solaris Flash creation software removes all RAID-1 volume information from the archive to keep the integrity of the clone system. With custom JumpStart you can rebuild the RAID-1 volumes by using a JumpStart profile. With Solaris Live Upgrade, you create a boot environment with RAID-1 volumes configured and install the archive. The Solaris installation program cannot be used to install RAID-1 volumes with a Solaris Flash archive. For examples of RAID-1 volumes in JumpStart profiles, see Profile Examples in Solaris Express Installation Guide: Custom JumpStart and Advanced Installations.	Veritas VxVM stores configuration information in areas not available to Solaris Flash. If Veritas VxVm file systems have been configured, you should not create a Solaris Flash archive. Also, Solaris install, including JumpStart and Solaris Live Upgrade do not support rebuilding VxVM volumes at installation time. Therefore, if you are planning to deploy Veritas VxVM software using a Solaris Flash archive, the archive must be created prior to configuring the VxVM file systems. The clone systems must be then configured individually after the archive has been applied and the system rebooted.

RAID Volume Name Requirements and Guidelines for Custom JumpStart and Solaris Live Upgrade

Observe the following rules when assigning names for volumes.

Use a naming method that maps the slice number and disk number to volume numbers.
Volume names must begin with the letter d followed by a number, for example, d0.
Solaris Volume Manager has 128 default volume names from 0–127. The following list shows some example volume names.
- Device /dev/md/dsk/d0 – block volume d0
- Device /dev/md/dsk/d1 – block volume d1
Use ranges for each particular type of volume. For example, assign numbers 0–20 for RAID-1 volumes, and 21–40 for RAID-0 volumes.

RAID Volume Naming Conventions for Solaris Live Upgrade

When you use the Solaris Live Upgrade to create RAID-1 volumes (mirrors) and RAID-0 volumes (submirrors), you can enable the software to detect and assign volume names, or you can assign the names. If you enable the software to detect the names, the software assigns the first mirror or submirror name that is available. If you assign mirror names, assign names ending in zero so that the installation can use the names ending in 1 and 2 for submirrors. If you assign submirror names, assign names ending in 1 or 2. If you assign numbers incorrectly, the mirror might not be created. For example, if you specify a mirror name with a number that ends in 1 or 2 (d1 or d2), Solaris Live Upgrade fails to create the mirror if the mirror name duplicates a submirror's name.

Note - In previous releases, an abbreviated volume name could be entered. Starting with the Solaris Express 2/07 release, only the full volume name can be entered. For example, only the full volume name, such as /dev/md/dsk/d10, can be used to specify a mirror.

Example 9-1 Solaris Live Upgrade: Enable the Software to Detect and Name the Mirror and Submirror

In this example, Solaris Live Upgrade assigns the volume names. The RAID-1 volumes d0 and d1 are the only volumes in use. For the mirror d10, Solaris Live Upgrade chooses d2 for the submirror for the device c0t0d0s0 and d3 for the submirror for the device c1t0d0s0.

lucreate -n newbe -m /:/dev/md/dsk/d10:mirror,ufs -m /:/dev/dsk/c0t0d0s0:attach -m /:/dev/dsk/c1t0d0s0:attach

Example 9-2 Solaris Live Upgrade: Assign Mirror and Submirror Names

In this example, the volume names are assigned in the command. For the mirror d10, d11 is the name for the submirror for the device c0t0d0s0 and d12 is the name for the submirror for the device c1t0d0s0.

lucreate -n newbe -m /:/dev/md/dsk/d10:mirror,ufs -m /:/dev/dsk/c0t0d0s0,/dev/md/dsk/d11:attach
-m /:/dev/dsk/c1t0d0s0,/dev/md/dsk/d12:attach

For detailed information about Solaris Volume Manager naming requirements, see Solaris Volume Manager Administration Guide.

RAID-Volume Naming Conventions for Custom JumpStart

When you use the custom JumpStart installation method to create RAID-1 volumes (mirrors) and RAID-0 volumes (submirrors), you can enable the software to detect and assign volume names to mirrors, or you can assign the names in the profile.

If you enable the software to detect the names, the software assigns the first volume number that is available.
If you assign names in the profile, assign mirror names ending in zero so that the installation can use the names ending in 1 and 2 for submirrors.

Note - If you assign numbers incorrectly, the mirror might not be created. For example, if you specify a mirror name with a number that ends in 1 or 2 (d1 or d2), JumpStart fails to create the mirror if the mirror name duplicates a submirror's name.

Note - You can abbreviate the names of physical disk slices and Solaris Volume Manager volumes. The abbreviation is the shortest name that uniquely identifies a device. Examples follow.

A Solaris Volume Manager volume can be identified by its dnum designation, so that, for example, /dev/md/dsk/d10 becomes simply d10.
If a system has a single controller and multiple disks, you might use t0d0s0, but with multiple controllers use c0t0d0s0.

Example 9-3 Enable the Software to Detect the Mirror and Submirror Names

In the following profile example, the mirror is assigned the first volume numbers that are available. If the next available mirror ending in zero is d10, then the names d11 and d12 are assigned to the submirrors.

filesys                 mirror c0t0d0s1  /

Example 9-4 Assigning Mirror and Submirror Names

In the following profile example, the mirror number is assigned in the profile as d30. The submirror names are assigned by the software, based on the mirror number and the first available submirrors. The submirrors are named d31 and d32.

filesys                 mirror:d30 c0t1d0s0 c0t0d0s0  /

For detailed information about Solaris Volume Manager naming requirements, see Solaris Volume Manager Administration Guide.

Guidelines for Selecting Disks and Controllers

When you choose the disks and controllers that you want to use to mirror a file system, consider the following guidelines.

Use components that are on different controllers to increase the number of simultaneous reads and writes that can be performed.
Keep the slices of different submirrors on different disks and controllers. Data protection is diminished considerably if slices of two or more submirrors of the same mirror are on the same disk.
Organize submirrors across separate controllers, because controllers and associated cables tend to fail more often than disks. This practice also improves mirror performance.
Use the same type of disks and controllers in a single mirror. Particularly in old SCSI storage devices, different models or brands of disk or controller can have widely varying performance. Mixing the different performance levels in a single mirror can cause performance to degrade significantly.

Guidelines for Selecting Slices

When you choose the slices that you want to use to mirror a file system, consider the following guidelines.

Any file system, including root (/), swap, and /usr, can use a mirror. Any application, such as a database, also can use a mirror.
Make sure that your submirror slices are of equal size. Submirrors of different sizes result in unused disk space.
If you have a mirrored file system in which the first submirror attached does not start on cylinder 0, all additional submirrors you attach must also not start on cylinder 0. If you attempt to attach a submirror starting on cylinder 0 to a mirror in which the original submirror does not start on cylinder 0, the following error message is displayed:
```
can't attach 
labeled submirror to an unlabeled mirror 
```
You must ensure that all submirrors you plan to attach to a mirror either all start on cylinder 0, or that none of them start on cylinder 0.
Starting cylinders do not have to be identical across all submirrors, but all submirrors must either include or not include cylinder 0.