Table of Contents
Advertisement
2.9 Tape drives and sizing
In this section we discuss the calculations for estimating the size of a tape library
to support a Tivoli Storage Manager solution. Similar calculations can be used to
determine the total disk storage needed to support an environment.
Most Tivoli Storage Manager designs incorporate tape and tape drives as the
ultimate long-term storage locations for backups and archives. Therefore, it is
important to understand the performance characteristics of tape drives and tapes
when designing a Tivoli Storage Manager solution.
When using tape storage pools, a Tivoli Storage Manager server should have
access to no less than two drives. For architecture calculation purposes, assume
only 80% of maximum, uncompressed throughput for a tape drive. Be prepared
to do restores while other administrative operations are happening on the system
or when drives are broken.
Carefully consider card and bus throughput when attaching tape drives to
systems. Most protocol/tape combinations can accommodate two or three tape
drives per card. When using Fibre Channel/SAN attached tape drives and disks,
do not mix disk and tape traffic on the same HBA.
When planning for tape drive throughput and tape capacity, it is best to be
conservative. Although drives can perform close to and better than their
compressed rating, typically their performance is far less than this in reality. We
use 80% of native uncompressed throughput ratings and 150% of native capacity
ratings for theoretical calculations of drive throughput and tape capacity.
Table 2-14 summarizes those calculations for some popular tape drives.
Table 2-14 Tape device comparisons
Tape drive
Native speed
(MBps)
IBM LTO Gen 2
35
IBM LTO Gen 3
80
IBM 3590-E1A
14
IBM 3590-H1A
14
IBM 3592
40
STK T9840C
30
STK T9940C
30
50
IBM Tivoli Storage Manager Implementation Guide
Native capacity
Assumed speed
(GB)
(GB/HR)
200
98
400
224
40
39
60
39
300
112
40
84
200
84
Assumed
capacity (GB)
300
600
60
90
450
60
300
Advertisement
Table of Contents
