NAS Executor e7000 v1 - Quick Start Guide

Product Overview
1-16 Compaq StorageWorks NAS Executor E7000 Quick Start Guide
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Virtual Replicator Elements
Virtual Replicator (VR) provides volume virtualization for the NAS device by
allowing for the creation of virtual disks (basic disks in Windows 2000) from VR
pools containing the LUNs managed on the SAN. VR pools are logical abstractions
that aggregate the disk space from one or more LUNs into a large set of disk blocks.
From the pool of blocks, VR virtual disks are created and presented to the operating
system as New Technology File System (NTFS) volumes. Virtual disks can be
enlarged at a later time when there is a need for more space.
When using VR, the following constraints should be reviewed:
• There is a maximum of 256 LUNs available to the connected NAS devices.
• If multiple LUNs are used to form a VR pool, they must all be from the same
HSG80 controller pair.
• LVM from Windows 2000 should not be used to manage VR disks. The two
management tools do not have an awareness of each other and compatibility
issues can arise between the two management tools.
• VR pools can consist of a maximum of eight storage units. Thus, a pool can
consist of a maximum of eight separate LUNs. Each LUN cannot exceed 1 TB in
size.
• A pool may contain a maximum of 8 TB of disk space, and the maximum virtual
disk size is 2 TB.
• The LUNs composing a VR pool must be treated synchronously. For example, if
LUNs 8, 9, and 10 are used to compose a single VR pool and LUN 9 is restored
from a backup, snapshot, or clone, the VR pool would be corrupted, resulting in
complete data loss.
• There is a limit to the number of virtual disks that can be carved out of a VR
pool. Currently, a maximum of eight virtual disks can be carved out of a single
pool.
• Each virtual disk must be presented as a drive letter or a mount point on the NAS
device for users and the operating system to be able to access the virtual disk.
Although it is possible to create a virtual disk and not map it to a drive letter or
mount point, neither the users nor the administrator would have access to the
storage space contained within that virtual disk.