HPlogo Communicator 3000 MPE/iX Release 6.5 (Non-Platform Software Release C.65.00) > Chapter 4 Data Center Management

DLT4000/DLT7000 Differential Tape Support on MPE/IX

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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 (C6382A/C6383A) - F/W SCSI interface (not a true F/W device see "Product Overview")

  • DLT7000 (C6374A/C6375A) - 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.05.07) 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.

Hardware Requirements

On HP 3000 S900 systems F/W SCSI Device Support is typically provided via the 28696A NIO F/W SCSI Device Adapter Card. At the time this article was written, there are two other possible F/W SCSI Device Adapter Cards.

NEITHER of these connection options is actually supported:

Unsupported connection Option #1 The 9x9KS "Core I/O Card" A3453-69210 exports a F/W SCSI interface. However, we do NOT, for performance reasons, support or recommend that a DLT be connected via this interface. The assumption is that this exported bus will also be shared with the system's internal disks and unpredictable and unacceptable performance may be seen when disks and DLT are accessed simultaneously (as during STORE/RESTORE). (Please read additional information in the Product Overview section for details on device performance.
Unsupported connection Option #2 The HP-HSC F/W DA A2969A is not supported on HP 3000 S900 systems. This card requires the existence of "Device Adapter Software" that has yet to be written for MPE/iX.

Physical connection of these devices is accomplished via "Fast/Wide/Differential SCSI" Cables such as C2911A, C2924A, C2925A etc.

NOTE: While DLT Libraries are available for purchase, support for these devices is very limited on HP 3000 S900 systems. There are currently no plans for supporting the DLT Libraries for "normal" MPE/iX operations such as BOOT, FCOPY or STORE. DLT Libraries are supported only when used in conjunction with a third party software package, Legato's "NetWorker." Inquiries about DLT Library support should be made directly to Legato.

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/sec1
DLT4000 (FW-SCSI)20Gbtye~2Mybte/sec~4Mybte/sec1
DLT7000 (FW-SCSI)35Gbtye~4Mbyte/sec~9Mybte/sec1

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.

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.

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 HP 3000 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 DDUMP

   io>  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: 0

   io> lp 4/4.2
   PATH: 4/4.2                                LDEV:
   ID: PSEUDO                                 TYPE: DA
   PMGR: TRANSPARENT_MGR                   PMGRPRI: 6
   LMGR:                                    MAXIOS: 0

   io> 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 DDUMP

   io> 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: 0

   io> lp 4/4.3
   PATH: 4/4.3                                LDEV:
   ID: PSEUDO                                 TYPE: DA
   PMGR: TRANSPARENT_MGR                   PMGRPRI: 6
   LMGR:                                    MAXIOS: 0

   io> lp 4/3
   PATH: 4/3                                  LDEV:
   ID: HP28696A                               TYPE: DA
   PMGR: SCSI_DAM                          PMGRPRI: 6
   LMGR:                                    MAXIOS: 0



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