Technical data

SunOS 5.5 Devices st(7D)
target=1 lun=0;
name="st" class="scsi"
target=2 lun=0
tape-config-list =
"Magic DAT", "Magic 4mm Helical Scan", "magic-data"
magic-data = 1,0x34,1024,0x1639,4,0,0x8c,0x8c,0x8c,3;
name="st" class="scsi"
target=3 lun=0;
.
.
.
name="st" class="scsi"
target=6 lun=0;
Large Record Sizes
SPARC ONLY
To support applications such as seismic programs that require large record sizes, the flag
ST_NO_RECSIZE_LIMIT must be set in drive option in the configuration entry. A SCSI
tape drive that needs to transfer large records should OR this flag with other flags in the
’options’ field in st.conf. Refer to Tape Configuration. By default, this flag is set for the
built-in config entries of Archive DAT and Exabyte drives.
If this flag is set, the st driver issues a SCSI-2 READ BLOCK LIMITS command to the dev-
ice to determine the maximum record size allowed by it. If the command fails, st contin-
ues to use the maximum record sizes mentioned in the mtio(7I) man page.
If the command succeeds, st restricts the maximum transfer size of a variable-length dev-
ice to the minimum of that record size and the maximumDMA size that the host adapter
can handle. Fixed-length devices are bound by the maximum DMA size allocated by the
machine. Note that tapes created with a large record size may not be readable by earlier
releases or on other platforms.
Refer to the WARNINGS section for more information.
EOT Handling The Emulex drives have only a physical end of tape (PEOT); thus it is not possible to write
past EOT. All other drives have a logical end of tape (LEOT) before PEOT to guarantee
flushing the data onto the tape. The amount of storage betweenLEOT and PEOT varies
from less than 1 Mbyte to about 20 Mbyte, dependingon the tape drive.
If EOT is encountered while writing an Emulex, no error is reported but the number of
bytes transferred is zero and no further writing is allowed. On all other drives, the first
write that encountersEOT will return a short count or zero. If a short count is returned,
then the next write will return zero. After a zero count is returned, the next write returns
a full count or short count. A following write returns zero again. It is important that the
number and size of trailer records be kept as small as possible to prevent data loss.
Therefore, writing after EOT is not recommended.
Reading pastEOT is transparent to the user. Reading is stopped only by readingEOF’s.
For 1/2” reel devices, it is possible to read off the end of the reel if one reads past the two
file marks which mark the end of recorded media.
modified 30 Aug 1995 7D-309