Chapter 11Creating RAID-1 Volumes (Mirrors) During Installation (Planning)
This chapter describes the requirements and guidelines that are necessary to create mirrored file systems with the custom JumpStart or Solaris Live Upgrade installation methods.
This chapter describes the following topics.
For additional information about planning to create mirrored file systems with the Solaris Live Upgrade installation method, see General Guidelines for Creating Mirrored File Systems.
For instructions about how to create mirrored file systems with the custom JumpStart installation method, see filesys Profile Keyword (Creating Mirrored File Systems) and metadb Profile Keyword (Creating State Database Replicas).
System Requirement
To create mirrored file systems on specific slices, the disks that you plan to use for mirroring must be directly attached and available to the system during the installation.
Volume Name Requirements and Guidelines
The custom JumpStart installation method automatically assigns volume names to RAID-0 submirrors during the installation. You can optionally assign a name to RAID-1 volumes (mirrors) with the filesys JumpStart keyword.
Observe the follwoing rules when assigning names for volumes.
Volume names must begin with the letter d followed by a number, for example, d0.
Instead of specifying the full volume name, such as /dev/md/dsk/d1, you can often use an abbreviated volume name, such as d1.
To simplify the administration of volumes, consider using the following standard naming conventions.
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.
When you use Solaris Live Upgrade to create mirrors, use a naming relationship for mirrors. You can name mirrors with a number that ends in zero (0), and submirrors that end in one (1) and two (2). Examples are mirror d10, submirrors d11 and d12, and mirror d20, submirrors d21 and d22.
When you use the custom JumpStart installation method to create mirrors, the submirrors are automatically assigned a name that corresponds to the name of the mirror.
Use a naming method that maps the slice number and disk number to volume numbers.
Solaris Volume Manager has 128 default volume names from 0-127. The following list shows some example volume names.
For detailed information about Solaris Volume Manager naming requirements, see Solaris Volume Manager Administration Guide.
State Database Replicas Guidelines and Requirements
You should distribute state database replicas across slices, drives, and controllers, to avoid single points of failure. You want a majority of replicas to survive a single component failure. If you lose a replica, when a device fails, for example, the failure might cause problems with running Solaris Volume Manager software or when rebooting the system. Solaris Volume Manager software requires at least half of the replicas to be available to run, but a majority (half plus one) to reboot into multiuser mode.
For detailed instructions about creating and administering state database replicas, see Solaris Volume Manager Administration Guide.
Selecting Slices for State Database Replicas
Before selecting slices for state database replicas, consider the following guidelines and recommendations.
You should create state database replicas on a dedicated slice of at least 4 Mbytes per replica. If necessary, you could create state database replicas on a slice that is to be used as part of a RAID-0 or RAID-1 volume. You must create the replicas before you add the slice to the volume.
By default, the size of a state database replica is 4 Mbytes or 8192 disk blocks. Because your disk slices might not be that small, you can resize a slice to hold the state database replica. For information about resizing a slice, see "Administering Disks (Tasks)" in System Administration Guide: Basic Administration.
You can create state database replicas on slices that are not in use. The part of a slice that is reserved for the state database replica should not be used for any other purpose.
You cannot create state database replicas on existing file systems, or the root (/), /usr, and swap file systems. If necessary, you can create a new slice (provided a slice name is available) by allocating space from swap and then put state database replicas on that new slice.
When a state database replica is placed on a slice that becomes part of a volume, the capacity of the volume is reduced by the space that is occupied by the replica or replicas. The space that is used by a replica is rounded up to the next cylinder boundary and this space is skipped by the volume.
Choosing the Number of State Database Replicas
Before choosing the number of state database replicas, consider the following guidelines.
A minimum of 3 state database replicas are recommended, up to a maximum of 50 replicas per Solaris Volume Manager disk set. The following guidelines are recommended:
For a system with only a single drive: put all three replicas in one slice.
For a system with two to four drives: put two replicas on each drive.
For a system with five or more drives: put one replica on each drive.
Additional state database replicas can improve the mirror's performance. Generally, you need to add two replicas for each mirror you add to the system.
If you have a RAID-1 volume that is to be used for small-sized random I/O (for example, for a database), consider your number of replicas. For best performance, ensure that you have at least two extra replicas per RAID-1 volume on slices (and preferably on disks and controllers) that are unconnected to the RAID-1 volume.
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