User manual

Using S.M.A.R.T. Disk Monitor 145
SANTOOLS® is registered in US Patent and Trademark Office No 3,107,854 All rights reserved.
Compression Efficiency
Hardware or software compression, which is best? How do you tell if hardware compression is enabled on the tape
drive? (See the DCE setting ) The answer is that it depends. Our software will provide you the tools you need to
measure true compression, compare different algorithms (if your tape is equipped), and see if your tape operates
more efficiently using one method or another. The information below comes from viewing the log pages after a
backup run. Further down, you will see some configurable mode pages parameters and settings.
Just run smartmon-ux -Cx before and after a test run, and use the results to establish effectiveness of your
settings down to the exact byte count.
Total logical data blocks transferred: 7248
Total physical blocks written to media: 55023104
Total physical blocks read from media (Read and Space operations only): 101376
Write compression ratio (percentage - reset on cartridge change): 168
Read compression ratio (percentage - reset on cartridge change): 0
Percentage of data with compression between .89 and 1.2 - reset on cartridge change: 0
Percentage of data with compression between 1.2 and 1.6 - reset on cartridge change: 28
Percentage of data with compression between 1.6 and 2.2 - reset on cartridge change: 71
Percentage of data with compression between 2.2 and 3.6 - reset on cartridge change: 0
Percentage of data with compression greater than 3.6 - reset on cartridge change: 0
Bytes processed (on Writes): 295436288
Unrecovered errors (on Writes): 0
Bytes processed (on Reads): 7602176
Tape Drive Configurable Mode Page Parameters
Our tandberg isn't very configurable (the R/O means the field is read-only), but other manufacturers provide much
greater room for tweaking settings. If you read the full manuals for the most popular software, you will find that they
usually provide "best practice" settings. You will be amazed at how much your performance may improve if your
buffer size is too small or too large, as an example.
Read-Write Error Recovery : Page [01h] (Factory, Current, Saved)
Transfer block (TB) : 0, 0, 0 {R/O}
Enable early recovery (EER) : 1, 1, 1 {R/O}
Post error (PER) : 0, 0, 0 {R/O}
Disable transfer on error (DTE) : 0, 0, 0 {R/O}
Disable correction (DCR) : 0, 0, 0
Read retry count (RRC) : 24, 24, 24
Write Retry Count (WRC) : 16, 16, 16
Disconnect-Reconnect : Page [02h] (Factory, Current, Saved)
Buffer full ratio (BFR) : 16, 16, 16
Buffer empty ratio (BER) : 16, 16, 16
Bus inactivity limit (BIL) : 0, 0, 0 {R/O}
Disconnect time limit (DTL) : 0, 0, 0 {R/O}
Connect time limit (CTL) : 0, 0, 0 {R/O}
Maximum burst size (MBS) : 0, 0, 0
Enable modify data pointers (EMDP) : 0, 0, 0 {R/O}
Fair arbitration (FA) : 0, 0, 0 {R/O}
Disconnect immediate (DImm) : 0, 0, 0 {R/O}
Data transfer disconnect control (DTDC) : 0, 0, 0 {R/O}
First burst size (FBS) : 0, 0, 0 {R/O}
Data Compression : Page [0Fh] (Factory, Current, Saved)
DCE : 1, 0, 1
DCC : 1, 1, 1 {R/O}
DDE : 1, 1, 1
RED : 0, 0, 0
Compression algorithm : 00000003h, 00000003h, 00000003h
Decompression algorithm : 00000000h, 00000003h, 00000000h
Tape Control : Page [10h] (Factory, Current, Saved)
Change active partition (CAP) : 0, 0, 0
Change active format (CAF) : 0, 0, 0 {R/O}
Active format : 0, 0, 0 {R/O}
Active partition : 0, 0, 0
Write buffer full ratio : 0, 0, 0 {R/O}
Read buffer empty ratio : 0, 0, 0 {R/O}
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