| The information below is approximate. Times will vary depending on
configuration and applications used.
TL81x/82x/89x Tape Library
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Q: How long does it take to locate a file on the device???
A: There are three variables to consider to derive a total time:
1. The time to move a cartridge to a drive which is the robot movement
time.
2. The time for the drive to mount a cartridge
3. The time to locate the file
---------------------------------
Total time to find the file on the device
Move a cartridge - Varies from 10 - 25 seconds
- AVERAGE is 15 seconds
Mount a cartridge - First mount is approximately 1 minute
- Subsequent mount varies from 35 - 45 seconds
Locate a file - Depends on where the file is on the tape
- Maximum is 90 seconds to end of tape
- Average is 45 seconds
- Nominal is 30 seconds
TOTAL TIME EXAMPLES:
First Cartridge Mount:
15 seconds + 1 minute + 45 seconds = 2 minutes/cartridge
Subsequent Cartridge Mount:
15 seconds + 40 seconds + 45 seconds = 1 min, 40 sec./cartridge
COMPETITIVE COMPARISON:
It is important to be sure that matching comparisons of volumes are used,
otherwise the times above do not give an accurate comparison.
Per Cartridge: (In 2:1 compression mode)
TZ89 = 70 Gb = 1 cartridge
TZ88 = 40 Gb = 1 cartridge
TZ87 = 20 Gb = 1 cartridge
Example:
TZ87 = 20 Gb = 1 cartridge
8MM = 5 Gb = 4 cartridges
3480 = 500 Mb = 40 cartridges
3490 = 1 Gb = 20 cartridges
Therefore, if a file is on the last volume of an 8MM, the time would need to
be a multiple of 4 in order to make an accurate comparison with the DLT.
CONCLUSION:
DLT "WINS" per Volume but not per Cartridge.
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| (.0 hung with anetwork partner exit so here is the text.
.2 nicely anticipated the questions)
I have a customer planning to use a TZ887 and TL826 for an archiving
application.
Can you help with some information on the following questions:
1. Tape set up time for extracting a cartridge from TZ887 stacker and
mounting in the drive. Same info for TL826.
2. min, max and average time to find the start of a file in a 20GB(native) tape
3. Does the 2.5mb/sec transfer speed apply to writes and reads?
4. Does blocking factor/size affect DLT tape capacity?
-20GB native capacity constant or depends on blocking size?
-Any technical papers describing the physical layout of DLT tape
(header, segments, blocks, gaps, index, etc)?
The customer is looking at using Polycenter Sequential Media File System
software, ovms and sequential files on tape for archive data.
Thanks in advance
_Tony
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