by Larry Nichoalds, CSY Labs
Jim
Hawkins, SSD WTEC
Beginning with Release 5.5 Express 7, MPE/iX supports the
following stand-alone Differential DLT Tape drives:
DLT4000 (C3690A) - F/W SCSI interface (not a true
F/W device see "Product Overview")
DLT7000 (C6374A) - F/W SCSI interface
Software Requirements |
 |
Customers wishing to use these new DLT devices must be running
on MPE/iX 5.5 or LATER version of MPE/iX. On MPE/iX 5.5 (Release
C.55.00, MPE/iX 31900C.05.08) a patch provides the critical software
device driver enhancements necessary for the support of these DLTs.
Again, these devices are NOT supported on MPE/iX 5.0 (Release C.50.00, 31900B.79.06)
and there are no plans to support these devices on 5.0 in the future.
Upon the release of Release 6.0 Express 1, there will not
immediately be any patches for Predictive Support or Online Diagnostics
that specifically support the new device IDs. In the short term
Predictive and Diagnostic tools will likely flag these devices as "unknown" or "unsupported." However,
the SCSIDLT diagnostic will function for these devices AND plans
are in place to include Predictive and Diagnostics in the next open Express/PowerPatch
Release for 5.5.
Product Overview |
|
| Product | Standard, Non-compressed Capacity with DLT
IV | Average Maximum Data Transfer Rate to Tape | Average Maximum Data Transfer Rate on SCSI
Bus | Maximum of Devices per Bus |
|---|
| DLT4000 (SE-SCSI) | 20Gbtye | ~2Mbyte/sec | ~4Mbyte/sec | 1 |
| DLT4000 (FW-SCSI) | 20Gbtye | ~2Mybte/sec | ~4Mybte/sec | 2 |
DLT7000 (FW-SCSI) | 35Gbtye | ~4Mbyte/sec | ~9Mybte/sec | 1 |
The performance difference between the DLT4000 and DLT7000
Differential drives is due to data transfer characteristics. Specifically
the DLT7000 is a "differential-wide" device, transferring
two bytes at a time during the data phase. The DLT4000 (C3690A),
though it is connected via a "differential-wide" cable,
is actually a "differential-narrow" device, transferring
only one byte at a time. From a native (non-data compression) perspective, the
DLT4000 is capable of transferring data to tape at up to 2 Mb/Sec
while the DLT7000 is capable of transferring data to tape at up
to 4 Mb/Sec. When making use of the compression feature (Digital
Lempel-Ziv, DLZ) the amount of data sent to the device can be significantly
greater than the device's ability to write to tape, depending
on the compressibility of data. However, there is an upper limit
on the amount of data that the device can accept and the SCSI bus
can transfer. This puts an upper limit on the number of devices
that can be driven at peak I/O rates on a Bus. This upper limit
is the "Maximum Number of Devices Per Bus." Of
course, these figures are approximate and are reached only on systems
with sufficient available CPU resources AND Disk I/O bandwidth.
Both the DLT4000 and DLT7000 drives accept the new CompacTape
IV cartridge. When this cartridge is used, the amount of data you
can store on a tape can be up to 20.0 GB native, or an expected
40.0 GB of data using the compression mode for the DLT4000. The DLT7000
will hold 35.0 GB native, or 70.0 GB when employing data compression.
The actual amount of data stored in compression mode is dependent
on the nature of the data being stored. That is, text files tend
to be highly compressible while code files are not. Both devices
can also use the CompacTape III cartridge. The amount of data you
can store on this tape cartridge can be 10.0 GB native capacity
or 20.0 GB compressed.
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|
 | IMPORTANT: Tapes created on a DLT4000 can always be read by
the DLT7000; however, DLT4000 drives are not capable of reading
tapes created on DLT7000s. Since both drives use the same physical
media type, shops with a mixture of DLT types will have to manage
media created on DLT7000 separately so as not to attempt to read
it on a DLT4000. Typically if a DLT7000 tape is put into a DLT4000,
the "Use Cleaning Tape" indicator will be illuminated.
If a DLT7000 tape is to be over-written by a DLT4000, just ignore
the "Use Cleaning Tape" indicator and proceed
overwriting the tape (do not clean the drive). The "Use
Cleaning Tape" will go off automatically when the tape
is overwritten or removed from the drive. |
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| |
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DLT is designed as a high-volume back-up solution. The tape
media can endure approximately 500,000 passes and has a shelf life
of 10 years. The DLT4000 has a head life of 10,000 tape motion hours
and MTBF of 80,000 based on a 100% duty cycle. The DLT7000 has a
head life of 30,000 tape motion hours and MTBF of 200,000 hours
with a 100% duty cycle (per Quantum's literature). Unlike
DDS drives, you should only clean DLT devices when the cleaning
light actually comes on. If you clean a DLT more often than is indicated,
you will reduce the life of the heads.
Configuration |
|
Here is an example of what the configuration should look like
on the HP3000 for the DLT4000 and DLT7000.
DLT4000 Example
io> ld 90
LDEV: 90 DEVNAME: OUTDEV: 0 MODE:
ID: DLT4000 RSIZE: 128 DEVTYPE: TAPE
PATH: 4/4.2.0 MPETYPE: 24 MPESUBTYPE: 8
CLASS: TAPE DLTTAPE DDUMPio> lp 4/4.2.0
PATH: 4/4.2.0 LDEV: 90
ID: DLT4000 TYPE: TAPE
PMGR: SCSI_TAPE2_DM PMGRPRI: 10 LMGR:
LOGICAL_DEVICE_MANAGER MAXIOS: 0io> lp 4/4.2
PATH: 4/4.2 LDEV:
ID: PSEUDO TYPE: DA
PMGR: TRANSPARENT_MGR PMGRPRI: 6
LMGR: MAXIOS: 0io> lp 4/4
PATH: 4/4 LDEV:
ID: HP28696A TYPE: DA
PMGR: SCSI_DAM PMGRPRI: 6
LMGR: MAXIOS:DLT7000 Example
io> ld 91
LDEV: 91 DEVNAME: OUTDEV: 0 MODE:
ID: DLT7000 RSIZE: 128 DEVTYPE: TAPE
PATH: 4/4.3.0 MPETYPE: 24 MPESUBTYPE: 8
CLASS: TAPE DLTTAPE DDUMPio> lp 4/4.3.0
PATH: 4/4.3.0 LDEV: 90
ID: DLT7000 TYPE: TAPE
PMGR: SCSI_TAPE2_DM PMGRPRI: 10
LMGR: LOGICAL_DEVICE_MANAGER MAXIOS: 0io> lp 4/4.3
PATH: 4/4.3 LDEV:
ID: PSEUDO TYPE: DA
PMGR: TRANSPARENT_MGR PMGRPRI: 6
LMGR: MAXIOS: 0io> lp 4/3
PATH: 4/3 LDEV:
ID: HP28696A TYPE: DA
PMGR: SCSI_DAM PMGRPRI: 6
LMGR: MAXIOS: 0
