IBM Tape Library Magstar 3494, Руководство оператора

Страница: 190 / 378

Five drop-down lists and a set of check boxes are used to set up an inhibit reclaim
entry. The drop-down lists contain the following:
v
Day of week
Sunday through Saturday or Every day. If “Every day” is selected, the “Start time”
and “Duration” entered will apply to every day of the week.
v
Start Hour and Minute
The start hour and minute for the inhibit. A 24 hour clock is used where 00 in the
hour field means midnight.
v
Duration Hours and Minutes
The number of hours and minutes that the inhibit reclaim should remain in effect.
Up to 167 hours and 59 minutes can be specified (7 days minus 1 minute).
Specifying the maximum will essentially always inhibit reclaim.
v
Check boxes to indicate which VTS to apply the schedule to.
Add an entry to the inhibit reclaim schedule by selecting a day of week, a start time,
the duration, then select the Add button.
Delete an entry by highlighting it in the list box then selecting the Delete button.
The Free Storage Threshold is used to provide a warning when the VTS is running
low on free storage, the capacity of all the empty stacked volumes in the VTS. A
threshold is provided for each VTS installed in the library and is entered in GB. The
default value is 100 GB. The VTS Active Data window displays the Free Storage
Threshold as the Free Storage Alarm Level. If the free storage drops below the
threshold (alarm level), the Library Manager signals an intervention-required
condition to notify the operator to add more stacked volumes.
The number of stacked volumes required to store the Free Storage Threshold GB
specified on the Set VTS Management Policies window is dependent on the
compression of data when writing from the Tape Volume Cache to the stacked
volume. The 3494-B18 VTS with enhanced ESCON host attachments provides
compression into the Tape Volume Cache; therefore, further compression when
writing to the stacked volume is unlikely, and the capacity of a stacked volume will
be approximately 10 GB of Tape Volume Cache data. The earlier VTS, 3494-B16,
relied on the compression capability of the Magstar 3590 drives to store
approximately 20 GB of Tape Volume Cache data, assuming a compression ratio of
2:1.
The Free Storage Threshold of 100 GB requires five empty cartridges for the model
B16 VTS; however, with the model B18 VTS, a Free Storage Alarm is sent when
only 10 empty stacked volumes are available because the Tape Volume Cache data
has already been compressed when received into the Tape Volume Cache.
Assuming a compression ratio of 3:1 with the enhanced ESCON host attachments,
an alarm at the Free Storage Threshold of 100 GB, representing 10 empty stacked
volumes, allows storage of 300 GB of logical volume data.
To get an alarm when the number of empty stacked volumes drops below 50, you
would specify a Free Storage Threshold of 500 GB on a model B18 with enhanced
ESCON attachments, and of 1000 GB on other VTS models.
The
Reclaim Threshold Percentage
is used to identify when a stacked volume is to
be made available for reclamation. Each stacked volume has some amount of
active data and some amount of inactive (no longer needed) data. If the percentage
of active data is less than the percentage specified in this panel, the stacked
168
Magstar 3494 Tape Library Operator Guide
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|