IBM System Storage TS3500, Введение и руководство по планированию

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row y always keeps the same WWN, even if the drive is replaced. The design of a
WWN is such that if a drive needs service or replacement, host parameters do not
need to be changed or reconfigured. The library's configuration can also easily
survive a reboot. The following sections describe methods that involve World Wide
Names in resolving these issues.
Using persistent binding to ensure SCSI ID assignment
When a server is booted, devices are discovered and assigned SCSI target and
LUN IDs. It is possible for these SCSI assignments to change between boots. Some
operating systems do not guarantee that devices will always be allocated the same
SCSI target ID after rebooting. Also, some software depends on this association, so
you do not want it to change. The issue of SCSI ID assignment is addressed by
persistent binding.
Persistent binding is a host bus adapter (HBA) function that allows a subset of
discovered targets to be bound between a server and device. Implemented by a
World Wide Node Name (WWNN) or World Wide Port Name (WWPN), persistent
binding causes a tape drive's World Wide Name to be bound to a specific SCSI
target ID. After a configuration has been set, it survives reboots and any hardware
configuration changes because the information is preserved. If a drive needs to be
replaced, the new drive assumes the WWNN of the old drive because the WWNN
for the drive is location-dependent within the library. Because the WWNN does
not change, persistent binding does not need to be changed which would cause an
outage.
Using zoning to isolate devices and enhance security
For security reasons, it is important to limit the devices that a server or servers can
recognize or access. Also, some performance configurations and Storage Area
Network (SAN) configurations can result in a device being seen multiple times
from the same server. For example, if you have two host bus adapters (HBAs) from
the same server connected to a tape drive in the TS3500 Tape Library, the drive
will be detected and appear as two logical devices. That is, there will be two
special files for one physical device. Zoning can address these issues.
Zoning allows you to partition your SAN into logical groupings of devices so that
each group is isolated from the other and can only access the devices in its own
group. Two types of zoning exist: hardware zoning and software zoning. Hardware
zoning is based on physical fabric port number. Software zoning is defined with
the World Wide Node Name (WWNN) or World Wide Port Name (WWPN). While
zoning can be reconfigured without causing an outage, some zoning configurations
can become complicated. The advantage of the library's WWNN implementation is
that you can avoid the exposure of introducing zoning errors because you do not
have to change the zoning configuration if a drive needs service or replacement.
Connectors and adapters
This section provides Web sites that give information about the latest connectors
and adapters for the TS3500 Tape Library.
The TS3500 Tape Library is supported by a wide variety of servers (mainframe
hosts), operating systems, and adapters. These attachments can change throughout
the product's life cycle. To determine the latest attachments, visit the following
Web sites or contact your IBM Sales Representative.
Chapter 6. Using the Fibre Channel interface
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