Backup3G/User Guide/Managing Drives

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Revision as of 03:19, 19 April 2006

Backup3G supports all standard backup drive types, plus other writable tape and disk media. Additionally, the COS/Stacker module makes the configuration and management of autoloading devices such as stackers and jukeboxes easier to perform.

If you are not familiar with drive operations and issues such as logical versus physical drives, you may wish to read the background provided in Information on Drives and Drive Pools on page 65.

This section describes how to configure and operate drives and load devices in backup3G. The main topics covered are:

1. Adding new drives
2. Performing tape drive operations.

Before You Use a Removable Media Drive

To use a drive from a given host, backup3G needs to know:

• what media types the drive can use
• how to read data from and write data to the drive (the UNIX device name)
• how media will be loaded and unloaded.

These details are specified in the drive table of any backup3G host that runs a backup or recovery job using that drive. That is, if backups are run from different hosts the drive details should be added on each host (see About Drives and Drive Pools on page 66).

Figure 37 — Drive console

You should define a separate logical drive for each:

• media type this drive will read
• host machine the drive will be switched between
• loading method (manual or automatic) that will be used.

The steps to follow are:

1. Define a ‘media location’ for all the places where media can be stored before

being used in a drive—e.g. tape libraries, stacker devices etc.

1. If necessary, define drive and load operations. backup3G has drive and load

operations for a number of common drive and stacker types. If your drive is not covered by one of these you will need to specify the commands used to load and position media in the drive.

1. Add the drive details (see To add a removable media drive on page 136).

When a backup job is run, backup3G scans the media location for that drive to find available media of the correct type. So, you will need to add details of your tapes and diskettes to the media table before running any backups. See Managing Removable Media on page 115.

How To Add A New Tape or Disk Drive

To add a new drive, you must first check that the device file entry exists under /dev. Unless you are adding a new type of storage device, an entry will almost certainly exist. If not, see your operating system manual for information on how to create one.

The next step is to define the drive details to backup3G. These include the physical and logical drive names, the UNIX device name, and the drive type and description.

Backup3G can treat each physical drive unit as one or more logical drives, if it can:

• read and write multiple media types
• be switched between two hosts
• be loaded both manually and automatically

(see Physical and Logical Drives on page 68).

For each drive you will also specify the operations used to load and unload media, and for tape drives the class of commands used to manipulate media, such as skip, rewind and status. You can use existing UNIX file and tape-handling commands or add your own.

To add a removable media drive

1. Select backup3G configuration > Maintain drives and

stackers.

1. Select Maintain > Add.

Physical drive name Enter a name for the drive that is physically attached to the computer. This name is used to lock the drive, to avoid two or more jobs using the drive at the same time. Note that the name cannot contain the ‘forward slash’ character (“/”). Logical name Enter a logical drive name. If there is only one logical drive for this physical drive, use the same name for both. Managing Drives 137 Example: for a drive that supports both 1-GB and 2-GB DAT tapes, use a suffix to distinguish them, such as server1-DAT and server1-DAT-hi.

Figure 38 — Adding a drive (example)

Media type Press Choose to list the valid media types. Select a media type to associate with this logical drive. (To add a new media type, see Adding a New Media Type on page 124.) Drivehost Choose the name of the host machine to which this drive is physically attached. Device Enter the full path of the UNIX device name used to access this drive. Examples: /dev/tape, /dev/rmt/0m, /dev/rfd0 If the drive can be addressed as either a block device or a character or raw device, use the raw device name. Device (no rewind) If this is a tape drive that supports no-rewind, enter the no-rewind 138 Managing Drives device name. This is usually the same as the rewind device but with the letter ‘n’ added. Examples: /dev/ntape, /dev/rmt/0mn Description Enter a description. Example: “2GB DAT drive on server-1”. Operations class Select the class of commands that UNIX will use to perform physical operations (e.g. skip forward, rewind, scan) on media in this drive. Examples: mt, tapecntl, ctape. Operator msg This is an optional message that can be used to prompt the operator to perform some action before the drive is loaded. Example: “switch drive tape-2 from Host A to Host B”. Buffer size (KB) High-speed streaming devices such as DLT drives may be limited by the speed at which data can be passed to them. This field allocates an area in shared memory for devio(1) to use as a buffer, so that the drive is never waiting for data. Buffering may also improve the performance of network backups to slower tape drives. The most efficient setting can only be found through trial and error. You may allocate up to 16 MB if there is sufficient shared memory available. Leave this field blank to disable buffering. Loading location The location from where media are loaded into this drive. When a backup job requests new media for this drive, backup3G selects a scratch volume from this location. For a manually-loaded drive this is usually your main media library. If this drive is attached to a tape stacker, the loading location is the auto-loading device itself. The device is a media location of type ‘load_device’. To add a load device or media library, see Adding a New Media Location on page 116. Loading class The class of loader operations, or the command class used to load and unload the drive. For manually-loaded drives select the default option, ‘Manual loading and unloading’, or, if mt is available, select ‘manual-mt’. Drive position For an automatic tape library containing multiple drives, enter the position or number of this drive.

1. Press Accept to store details of your new drive.

Example: adding a QIC tape drive

You have attached a cartridge tape drive on your main host in order to read some old archive tapes in QIC-24 format. You also want to use the drive to write user backups to QIC-150 tapes.

In this case we will add two logical drives, one to use the higher capacity tapes and the other to use the lower. We will first define a logical drive called ‘mainhost-ct’, then repeat the process for ‘mainhost-ctlow’. (Substitute one of your host names for ‘mainhost’ in the following steps.)

1. From the ‘Removable Media Drive’ window, select Maintain > Add.

Physical drive name Enter the name of the physical drive – ‘mainhost-ct’. Logical name Enter the logical drive name – also ‘mainhost-ct’. Media type Press Choose to display the list of available media types. Select QIC-150. Drivehost Press Choose to list the hosts on your network. Select ‘mainhost’. Device Enter /dev/tape in the device name field Device (no rewind) Enter /dev/ntape as the no-rewind device. Description Enter ‘150 Mbyte tape cartridge’ 140 Managing Drives Operations class Press Select a few times to display the options for drive operations class. If mt is available on your system, select it, otherwise select ‘null’. Operator msg Leave this field blank. backup3G will generate a default message to prompt the operator to load the correct volume in the nominated drive. Buffer size (KB) As QIC drives are relatively slow, data buffering is not required. Leave blank. Loading location Select the location of your main tape library. Loading class Select ‘manual’.

Leave Drive position blank, as there is no auto-loading device attached to this drive.

You have now defined a logical drive to backup3G. You have named the physical tape drive to which it corresponds, identified the UNIX commands that will be used to access it, and selected the single media type that this drive will be used to read.

The next step is to define a second logical drive to read the lower capacity QIC-24 tapes.

1. Repeat step 2 on page 136.
2. Enter ‘mainhost-ctlow’ in the Logical name field.
3. Select media type ‘qic24’.
4. The remaining steps are the same. If you wish, you can change the descriptions

and operator messages to refer to the actual type of cartridge tape.

These logical drives are now available to be selected the next time you add or change a backup job. backup3G will use the commands you have just specified to load and position the tape before reading or writing data.

How To Perform Tape Drive Operations

You can use backup3G to perform a standard set of operations on tape drives, including skipping forward or backward through the tape, rewinding to the beginning, ejecting the tape or checking its status. These operations can either be performed through the drive management module, or automatically as a step in a duty or backup job.

Whether an operation can be performed on a particular drive depends on the capabilities of the device and the version of UNIX you use. backup3G will only display operations that can be performed on the selected drive. See also Physical unload on page 142.

How the operations are actually done also depends on your UNIX version. For example, most operations on cartridge and magnetic tape are carried out via mt or ctape. On systems that don’t support these commands, other commands or shell scripts may be used instead.

To operate a tape drive

1. Start the removable media drive management module.
2. From the list of drives displayed, select the drive you want to manipulate.

You can only select drives for which operations are defined.

1. The Operations menu contains the following options:
2. Select the operation you want to perform. If you select Skip fwd or Skip

back you will be prompted to enter the number of files. backup3G then runs the command for this operation that is defined in the Display Display drive operations for the selected drive Status The current status of this drive Unload Unload the volume from this drive Rewind Rewind tape to the first file Skip fwd Position tape past the next N end of file markers Skip back Position tape past the previous N end of file markers 142 Managing Drives ‘Drive Operations’ table.

What happens next depends on the hardware and operating system: if there are any error messages they will be displayed on the screen, successful operations are announced also. Additional operations on the same drive can be initiated as soon as the current operation is complete.

Physical unload

Some drives cannot be unloaded by a software command and must be physically unloaded. In these cases, backup3G’s unload command is used to perform a ‘logical’ unload which enables backup3G to keep track of drive status. So, if backup3G’s load command is used, its unload command should also be used for it to maintain an accurate record.

Drives that can be unloaded by a software command are also affected by this, since users can bring about inaccuracies in backup3G’s tables by using a UNIX unload command on a volume that was loaded by backup3G. Should this situation arise, you can use backup3G’s unload command to correct the record; while the task will appear to fail because the volume has already been unloaded, backup3G will in fact amend its own records correctly.