A

array

Short for storage array.

allocation policy

A virtual disk allocation policy is an option that specifies how disk group space is reserved for a virtual disk. Two choices exist:

• Allocate completely, which reserves the maximum capacity of a virtual disk at the time the snapshot is created.
• Allocate on demand, which reserves space for the snapshot, but only as data is stored in it. Because of competition for resources within the disk group, there is no guarantee with demand allocation that enough space will be available to completely contain the virtual disk maximum capacity, if that is required.

asynchronous mode

A data replication operation mode where host write I/O is complete to the host immediately when the data is transferred to the source virtual disk. Replication of the write data to the destination is handled in the background.

C

container

A container is virtual disk space that is preallocated for later use as a snapclone or a snapshot.

controller software (VCS / XCS)

Controller software is low-level software (firmware) used by array controllers to run a storage array. In HP Replication Solutions Manager environments, the arrays may be running VCS or XCS versions that support different features.

D

destination virtual disk

A virtual disk that is the recipient of replicated data from a source virtual disk in a DR group.

DR group

A data replication (DR) group is a logical group of virtual disks in a remote replication relationship with a corresponding group on another array. Hosts write data to the virtual disks in the source DR group, and the array copies the data to the virtual disks in the destination DR group. The virtual disks in a DR group fail over together, share a log, and preserve write order within the group. A pair of source and destination virtual disks is called a copy set.

DR group log size

The user-requested size for the DR I/O write log disk.

DR group source log disk group

The disk group that contains the I/O write log for the source DR group. 

DR group source system name

The name of the source system for the DR group.

  DR group source virtual disk

The name of the source virtual disk to be replicated on the destination system.

DR mode

The method of replication of a DR group. There is one mode of operation, source-to-destination, indicating that data can be written to the DR group source virtual disks, and that data is replicated to its destination virtual disks. Data cannot be written to the destination virtual disks. Replication occurs in one direction only.

A DR group mode is different from its role in the replication. Regardless of the mode, a group can be either a source or a destination in the relationship.

E

EVA

Enterprise Virtual Array. A family of HP StorageWorks enterprise class storage arrays.

 

F

failsafe mode

A DR group setting that automatically takes all DR group members off line when one source or destination member fails to maintain data consistency across all members. The state of the group is known as failsafe locked. This condition requires immediate intervention.

G

general purpose server

A server whose purpose is to run a variety of applications, including HP StorageWorks applications.

H

host

A computer that is connected to a storage array for the purpose of reading and writing data from the arrays' virtual disks.

host ports

Ports that connect to hosts using a Fibre Channel fabric. A Fibre Channel fabric consists of a group of interconnected Fibre Channel switches. A host is a computer that runs user applications and that accesses virtual disks created and presented by the controller pair. 

host port world wide name

Each Fibre Channel port that connects a controller to a host through a switch has a world wide name (WWN), which is derived from the system or node WWN. Each of the host ports on the controller pair has its own port WWN. The system (or node) WWN ends in zero.

host volume

Storage capacity that is defined and mountable by a host operating system. In HP Replication Solutions Manager, host volumes are disks or volumes that are reported by an enabled host..

I

initialization

A process that prepares the storage system for use by binding the controllers together into an operational pair and by establishing preliminary data structures on the disk array. Initialization also creates the first disk group, called the default disk group. A disk group is a set or pool of physical disk drives in which virtual disks can be created.

L

logical disk

The basic data container underlying a virtual disk in the controller software. It provides a contiguous array of data blocks that may be written and read. Also called a logical unit.

LUN

Logical Unit Number. The term LUN is a SCSI convention. The hosts see a virtual disk as a LUN. The LUN address you assign to a virtual disk for a particular host is the LUN where that host sees the virtual disk. The range of each available LUN addresses is 1 through 1023 in the host. The maximum number of LUNs associated with a single FCA is 1024. Only 1023 are available for virtual disks; LUN 0 is reserved and cannot be used for a unit LUN. 

LUN address

Each host sees a virtual disk as a LUN. The assigned LUN address to a virtual disk for a particular host is the LUN where that host sees the virtual disk. The range of each host's available LUN addresses is 1 through 255.

When creating a virtual disk, the next lowest LUN address available appears as the default selection in the drop-down list. The LUNs that appear are only the unused LUNs for the selected host. To specify another LUN, use the drop-down list to select the number.

M

management server

A server whose principal function is to run HP StorageWorks applications, such as HP Command View EVA and HP Replication Solutions Manager.

mount point

A host's file system path or directory name where a host volume (device) is accessed.

P

presentation

The array controller act of making a virtual disk accessible to a host computer

R

redundancy

The level to which user data is duplicated for protection. Redundancy is directly proportional to cost in terms of storage usage. The greater the level of data protection, the more storage space is required. Three types of redundancy are available in the EVA storage system:

• None (striping) Vraid0
• Moderate (striping with parity) Vraid5
• High (mirroring) Vraid1

redundancy level (Vraid)

Redundancy level (Vraid) refers to the method and extent of RAID data protection for a virtual disk.

remote copy

A replica virtual disk on the destination array.

resource

An object in the Replication Solutions Manager navigation pane; namely, DR groups, enabled hosts, host volumes, managed sets, storage systems, and virtual disks. Replication is performed using these resources.

S

selective presentation

A feature wherein the controller pair presents a virtual disk only to the host computers permitted to use it. When you create a virtual disk, you may choose to permit only certain hosts to access that virtual disk. You can modify the permission for host access at any time.

snapclone

A snapclone is an independent, point-in-time copy of a virtual disk. It is independent because all of the data from the source virtual disk is copied to the snapclone.

snapshot

A snapshot is a dependent, point-in-time copy of a virtual disk. It is dependent because data is not actually copied to the snapshot until it is overwritten on the source.

storage array (storage system)

Refers to HP StorageWorks enterprise class storage products. The arrays include multiple physical disks, disk controllers and controller software.

 

 

U

uninitialized storage system

An uninitialized storage system consists of the raw HSV hardware only. The necessary software structures have not been configured on the system to make it available for data storage. An uninitialized system is labeled Uninitialized at the top of its properties page.

V

virtual disk type

There are three types of virtual disks:

• Original, which is the root or source Vdisk from which snapclones, snapshots, and mirrorclones are created.
• Snapshot, where the virtual disk is a snapshot of an original virtual disk or a mirrorclone.
• Snapclone, where the virtual disk is a snapclone of the original virtual disk. This virtual disk type exists only while the clone data is being copied.
• Mirrorclone, where the virtual disk is a local, mirrored copy of an original virtual disk.

Vraid0, no redundancy striping

A striped virtual disk is one in which the data from the host is broken into chunks and distributed on the disks comprising the disk group in which the virtual disk was created. Reading and writing to a striped virtual disk is fast and uses the available storage to its fullest, but there is no data protection (redundancy). See alsoredundancy. 

Vraid1, mirroring

Vraid1, or mirroring, provides the highest level of data protection. All data blocks are duplicated on separate physical disks. For read requests, the block is read from either disk, which can increase performance. Mirroring requires the most storage space; twice the storage capacity must be allocated for a given amount of data. See alsoredundancy.

Vraid5, moderate redundancy parity striping

Vraid5, or parity striping, is a data protection mechanism for a striped virtual disk. A striped virtual disk is one in which data from the host is broken into chunks and distributed onto the physical disks comprising the disk group in which the virtual disk was created. Another chunk (a parity chunk) is calculated from the set of data chunks and written to the physical disks. If one of the data chunks becomes corrupted, the data can be reconstructed from the parity chunk and the remaining data chunks. Parity striping gives moderate data protection. See alsoredundancy.

X

XCS

The firmware that runs on HSV2xx-series controllers.