IBM System Storage TS3500, Introduction And Planning Manual

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Table 27. Specifications for imports per hour and average I/O station drain time for a TS3500 Tape Library using one
active accessor (continued)
Notes:
1. The following library setup was used to obtain the stated performance data:
v
ALMS and virtual I/O slots are enabled
v
Cartridge assignment policy is setup for each logical library
v
No HD frames
Table 27 on page 86 lists the specifications for import performance only. Export
performance is designed to be within 20% of import performance when cartridges
are being exported from tier 0 and tier 1 slots. In other words, for recently used
cartridges and all cartridges in non-HD frames, exports per hour will be between
80% to 100% of imports per hour, and average I/O station fill time will be between
100% to 120% of the average I/O station drain time.
Table 28. Specifications for imports per hour for a TS3500 Tape Library with dual active
accessors and I/O Stations in both accessor zones
Library configuration (active frames)
1
Imports per hour
2,3
4 frames 1400
6 frames 1300
8 frames 1200
12 frames 1100
16 frames 1000
Notes:
1. Active frames are all frames in a dual-accessor library, except for service bays.
2.
The following library setup was used to obtain the stated performance data:
v
ALMS and virtual I/O slots are enabled
v
Cartridge assignment policy is setup for each logical library
v
No HD frames
3. The data assumes that the library is partitioned into two separate zones, such that the
cartridges assigned to the logical libraries in the two zones are imported and exported
using the I/O stations within each zone with no accessor path overlap.
Table 28 lists the specifications for import performance only. Export performance is
designed to be within 20% of import performance when cartridges are being
exported from tier 0 and tier 1 slots. In other words, for recently used cartridges
and all cartridges in non-HD frames, exports per hour range between 80% and
100% of imports per hour.
Import and export performance is impacted in a library with HD frames. For more
information, refer to “HD frame performance considerations.”
HD frame performance considerations
In HD frames, the cartridge accessor performs a shuffle operation in order to access
the cartridges stored in Tier 2 and beyond. A shuffle is the process of moving
cartridges in lower tiers into the gripper, or other available slots, in order to access
cartridges in higher tiers (Tier 2 or greater). In order to reduce the occurrence of
shuffle operations, and to take advantage of repeated accesses of certain cartridges,
the role of
cartridge cache is assigned to all single-deep (Tier 0) slots in an HD
library. In order to maintain efficient shuffle operations, the library performs a load
Chapter 1. Introduction
87