HP 3000 Manuals

TurboSTORE/XL II User's Guide

Storing to Multiple Tape Devices 

Multiple devices are identified as a pool of available devices.  When you
store to multiple devices, the devices must have similar characteristics;
different device types are not allowed.  The device characteristics that
must be identical are:

   *   All devices must be local.

   *   All devices must have the same density.

   *   All devices must have the same record size.

   *   All tapes must be either labeled or unlabeled; there cannot be a
       mix.

   *   All tape devices must be either DDS-format or magnetic tape; there
       cannot be a mix.

Multiple devices can be used as:

   *   Sequential devices.

   *   Parallel devices.

   *   Parallel device pools.

Whether you are using the sequential or parallel back up method:

   *   Decide on the order that each backup device in the pool is to be
       used.

   *   Assign each device a position based on its logical device (LDEV)
       number. 
       Figure 2-2  contains a chart to help you assign your devices.

   *   Select one of the methods in the chart, and enter the LDEV number
       of each device to be used and the order it is to be used.  For
       example, if you intend to use two parallel devices, write in the
       LDEV number of the first device next to device A and the LDEV
       number of the second device next to device B in the "Parallel"
       section of the chart.


          Figure 2-2.  Multiple-Device Planning Chart 

Using Tape Devices Sequentially 

With sequential tape devices, when the first backup tape on the first
backup device is filled, it immediately begins writing files to a second
tape on the second backup device and the first tape rewinds.  When the
first tape is rewound, you can unload it and prepare the drive with a new
tape.  You do not lose time while the first tape is rewinding nor while
you are loading a new tape.

When the tape on the last sequential device is filled, the process
returns to the first device.  It continues cycling through all the
devices in the device pool until all of the specified files are stored.

Figure 2-3  illustrates a sequential device backup.


          Figure 2-3.  Sequential Backup 

You can use a maximum of seven sequential backup devices.

Use the FILE command to give each device a file name that reminds you of
its position.  Then use the STORESET parameter in a STORE command to
reference the multiple devices.  For example, to store files to three
sequential devices, use the following set of commands: 

     FILE SEQ1;DEV=7 
     FILE SEQ2;DEV=8 
     FILE SEQ3;DEV=9 
     STORE @.@.@;;STORESET=(*SEQ1,*SEQ2,*SEQ3) 

The above STORE command copies all system and user files to three
sequential devices.  The parentheses surrounding backreferenced file
names group the devices into a device pool. 


NOTE  You do not backreference the file name of a backup device
      immediately after the name(s) of the file(s) you are storing when
      you use the STORESET parameter.  Instead, you must use a
      placeholder for the missing parameter normally supplied when using
      a single backup device.  The placeholder is provided by the use of
      ";;" in the STORE command.


If you gave the backup devices a single file name such as

     FILE T;DEV=TAPE 

enter the following STORE command to copy files to a set of three
sequential backup devices:

     STORE @.@.@;;STORESET=(*T,*T,*T) 


NOTE  Only unlabeled tapes can be used for a sequential device backup.


Using Tape Devices in Parallel 

With parallel devices, you have the capability of reducing backup time by
storing different files on different devices at the same time.  When you
store files to a set of parallel devices, the files are grouped before
the store begins and then copied to multiple devices simultaneously.  For
example, when you have three parallel devices, your files are partitioned
into three subsets.  Files in the first subset are copied to the first
tape drive, the files in the second subset are copied to the second tape
drive, and so on.  When a tape is filled, you are prompted to mount
another tape on that drive.

Depending upon the characteristics of your files and your backup devices,
storing files to parallel devices usually saves more time than using
sequential devices.

Figure 2-4  illustrates a parallel device backup.


          Figure 2-4.  Parallel Backup 

Currently, the TurboSTORE/XL II system configurations support a maximum
of eight parallel backup devices.  The actual speed of performance
depends on the system, disk configuration and the backup devices used.

To store files to a set of four parallel devices, the following set of
commands can be used:

     FILE PARA;DEV=7 
     FILE PARB;DEV=8 
     FILE PARC;DEV=9 
     FILE PARD;DEV=11 
     STORE @.OPERATOR.SYS;;& 
     STORESET=(*PARA),(*PARB),(*PARC),(*PARD) 

If you gave the backup devices a single file name such as

     FILE T;DEV=TAPE 

enter the following STORE command to copy files to a set of four parallel
backup devices:

     STORE @.@.@;;STORESET=(*T),(*T),(*T),(*T) 

Describe parallel devices in the STORESET parameter by enclosing each
backreferenced device file name within parentheses.  Use commas to
separate devices.

Using Parallel Device Pools 

Parallel device pools are multiple sets of sequential devices used in
parallel.  Using parallel device pools is often the most efficient way to
store a large set of files when you have several backup devices.
Parallel device pools give you the advantages of both parallel and
sequential devices.  You copy file subsets to different devices
simultaneously, and can have another sequential device ready when the
tape is filled in any device pool.

Figure 2-5  illustrates a parallel device pool backup.


          Figure 2-5.  Parallel Device Pools 

Up to eight backup devices are currently supported within a parallel
device pool.  For example, if you are using four sets of parallel
devices, you can use a maximum of two sequential devices within each set.
Maximum performance is obtained by using three or four parallel sets,
each consisting of two sequential devices.

To store files to parallel device pools, use parentheses to group the
devices into pools.  Separate the devices in the pool from one another
with commas.  Commas also separate each device pool.  For example, the
following commands copy files to two parallel device pools.  Each device
pool contains two sequential devices.  In the following example, STORE
uses a total of four devices divided into two device pools.

     FILE PPA1;DEV=7 
     FILE PPA2;DEV=8 
     FILE PPB1;DEV=9 
     FILE PPB2;DEV=11 
     STORE @.OPERATOR.SYS;;STORESET=(*PPA1,*PPA2),(*PPB1,*PPB2) 

If you gave the backup devices a single file name such as

     FILE T;DEV=TAPE 

enter the following STORE command to copy files to a set of parallel
device pools:

     STORE @.@.@;;STORESET=(*T,*T),(*T,*T) 
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MPE/iX 5.0 Documentation