assigns that path to the application. When another application opens a different device with
multiple HBA paths, the device driver again determines the path with the lowest HBA usage
and assigns that path to the second application. The device driver updates the usage on the
HBA assigned to the application when the device is closed. Dynamic load balancing uses all
HBAs whenever possible and balances the load between them to optimize the resources in
the machine.
Both CPF and DPF require the use of the IBM device driver, and are supported exclusively
with products that bear the IBM logo on the operating systems indicated in Table 1.
Table 1 summarizes the differences between CPF, DPF, and load balancing.
Table 1. Differences between DPF and CPF
Characteristic CPF DPF and Load
Balancing for
Ultrium 2 and
newer tape
drives
DPF and Load
Balancing for
3592 tape
drives
Device type SMC
1
SSC
2
SSC
LUN
3
LUN 1 LUN 0 LUN 0
Host-side failover Y
4
Y Y
Target-side failover Y N
5
Y
IBM device driver required Y Y Y
Operating systems supported
AIX
(R)
, SuSE
Linux
(TM)
, Red Hat
Enterprise Linux,
Solaris, Windows,
HP-UX, Asian UX
AIX, SuSE Linux,
Red Hat
Enterprise Linux,
Solaris, Windows
6
(DPF only), Asian
UX
AIX, SuSE Linux,
Red Hat
Enterprise Linux,
Solaris, Windows
6
(DPF only), HP-
UX, Asian UX
Order feature to obtain license key Y Y
7, 8
N
SCSI attachment supported Y N N
Fibre Channel attachment supported Y Y Y
Notes:
1. SMC = SCSI-3 Medium Changer Specification (library)
2. SSC = SCSI-3 Stream Commands (drive)
3. LUN = logical unit number
4. Y = Yes
5. N = No
6. Load balancing is not supported on Windows
7. For Ultrium 2 tape drives, DPF and load balancing do not require a license key on
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