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and thus availability. To do this, the HPSS administrator will need to:

•

Associate tape drives to a specific drive pool by configuring the HPSS tape drives with a non-zero
positive integer

Drive Pool ID

•

Modify the end client to dictate that their read request be serviced by tape drives from this
particular Drive Pool.

7.3.1. Tape Drive Configuration

To associate HPSS tape drives to a specific drive pool, an HPSS administrator will need to configure
HPSS tape drives with a non-zero positive integer

Drive Pool ID

. The

Drive Pool ID

can be set at

configuration time via the

Tape Device Configuration

window (Section 7.1:

Configure a New Device &

Drive

on page 196); it can be dynamically modified during runtime via the

PVL Drive Information

window (Section 7.2.2:

PVL Drive Information Window

on page 214) as long as the tape drive is locked

and free. To change the value during downtime, you must use the

Tape Device Configuration

window

and take down the HPSS servers associated with the tape drive: Mover, PVL and PVR. A

Drive Pool ID

of zero indicates the default Drive Pool.

7.3.2. Client Application Tape Read Requests

To make use of the Drive Pool feature, HPSS end client applications will need to be modified to dictate
that their read request be serviced by tape drives from this particular Drive Pool. This ability is only
available via the hpss_ReadList() API. The

Drive Pool ID

must be specified in the

ReqSpecInfo

structure

of the I/O Descriptor (IOD) passed to hpss_ReadList. This is accomplished by specifying
HPSS_IOD_SUBFUNC_DRIVE_POOL for the

SubFunction

and the

Drive Pool ID

for the

Argument

the

ReqSpecInfo

structure of the IOD. Refer to the

HPSS Programmer's Reference - I/O Supplement

for

more information.

7.3.3. Drive Pool Considerations

If HPSS receives an invalid

Drive Pool ID

or if the requested

Drive Pool ID

does not have the

appropriate drive type to handle the request, then the HPSS Client API will return an error to the client
for retry.

Since the

Drive Pool ID

is only used for read requests, all tape writes and tape migrations will use the

default

Drive Pool ID

. It is recommended that at least one tape drive remain in the default drive pool at

all times in order to satisfy these tape write requests.

Drive pool scheduling may not occur immediately since it could be the case that the drive was already
scheduled before the drive was locked and the

Drive Pool ID

was changed.

If a tape is being read and a request to read the same tape arrives within 45 seconds after the first request
completes, the Core Server will issue the I/O to the existing cartridge/drive. Once the drive transitions to
the Deferred Dismount state, a second request with a different

Drive Pool ID

will result in a dismount

and mount to a drive with the assigned

Drive Pool ID

Clients specifying different

Drive Pool ID

s for accesses to files from the same tape (or set of tape) may

result in more tape mount/unmount activity, depending upon timing. This is another reason why the drive
pool processing is restricted to tape read access only.

All mounts for striped tape volumes will be serviced from the same Drive Pool.

HPSS Management Guide

November 2009

Release 7.3 (Revision 1.0)

219