User`s guide

XStack Storage User’s Guide 25
The iSCSI protocol defines two types of iSCSI nodes:
 The initiator node
 The target node
The iSCSI initiator node consists of a name and a set of properties. The server’s operating system
provides software to define and configure its iSCSI initiator node. The XStack Storage unit serves
as one or more iSCSI target nodes. Section
5.3.5 describes how to use the XStack Storage
management console to define and configure iSCSI target nodes. Within each iSCSI target node,
one or more volumes can be accessed, using a Logical Unit Number (LUN), by one or more iSCSI
initiator nodes. Each iSCSI target node can have up to 256 LUNs. In the XStack Storage unit, the
LUNs available in one target node are independent from the LUNs in other target nodes.
The server (iSCSI initiator) “sees” the volumes by using the XStack Storage’s target node name
and a LUN. This combination creates a “circuit” between the Server operating system’s “disk
drive letter” (or Dynamic Volume) and the XStack Storage volume. XStack Storage is designed to
allow flexibility by granting specific initiator nodes access to specific target nodes. One initiator
can be given access to multiple target nodes, with different security mechanisms to protect
different applications. Access to volumes is controlled by the target node’s list of allowed LUNs.
2.3 Storage Pools and Drives
Storage space is managed on the XStack Storage unit through storage pools. The placement of a
drive in a storage pool controls the way that drive can be used. There are three types of storage
pools (refer to
Table 2-1).
Table 2-1 Types of Storage Pools
Storage Pool Usage
Available Pool Disk drives available for use, but with no data stored on them at this time. A spare
drive is normally kept in the available pool, so the drive is available for use should
any other drive fail.
Blade A Base Pool Disk drives currently being used to hold Volume data or ready to be used to hold
volume data.
Unusable Collection Two types of drives appear in the Unusable Collection:
 Drives not available for use either because they have already failed and have
not been removed from the enclosure
 Drives inserted into the XStack Storage unit that were found to be used
previously by an XStack Storage unit .
When a new system is installed, all new drives are placed in the available pool. The drives
remain in the available pool until they are needed for use in a volume or dragged and dropped by
the Administrator into the Blade A Base Pool.