Readability check is used to check the backup data readability. During the check the data on tape media is read in blocks, and the structure of tape is checked and recorded. It also checks whether all identified backup sets on the tape are recorded in the database and vice versa.
If the readability check cannot be performed for some reason, such as the medium being unavailable, the medium will be flagged as 'Readability check overdue'. When such media becomes available again, the readability check will be performed in order of oldest overdue medium first, according to the time it was first flagged as overdue. This ensures that the oldest overdue media are checked first.
To configure a readability check:
- You can determine the frequency and number of times the readability check is performed, as well as the grace period before a medium is flagged as overdue. This ensures that the readability checks are performed only when they are necessary, reducing the workload on the system and avoiding unnecessary wear and tear on the media.
- Then create a special media event and schedule the event for automatic execution.
- When a scheduled media event is triggered for a media pool, it checks whether any readability checks are due for the media in that pool. If a readability check is due according to the configured options, the media event performs the readability check (if the medium is available). If a readability check is not yet due, the media event skips over it until the next scheduled event.
You can also start a readability check immediately.
|The readability check can only be applied if a medium EOL has not expired; it is not applicable for EOL-free media. For details, see Tape media EOL.|
Setting up readability check on the media pool
You can specify the readability check settings when configuring a media pool or later in the media pool properties.
- From Main Selection -> Media Pools, click New Media Pool or double-click an existing media pool. The New Media Pool window or properties of the media pool opens. If you are creating a new media pool, specify the required fields, as explained in Configuring a Media Pool.
- Switch to the Readability Check tab and specify the following values:
- Readability check limit [days]: Specify how often (in days) the readability check will be performed. For example, setting it to 90 means that the check will be performed every 90 days, and setting it to 1 will activate a daily check. By default, the value is set to 0 (zero), which means that the readability check is turned off. If for some reason readability check cannot be performed (medium is busy or not loaded in the library), the medium is flagged as Readability check overdue.
- Expiration of read check overdue [days]: Specify the number of days after which a readability check is considered overdue. This setting adds an additional period before the medium is flagged as Readability check overdue. To calculate the time the value for this option is added to the value of Readability check limit option. For example, if Readability check limit is set to 90 and Expiration of read check overdue is set to 5, the medium is flagged as Readability check overdue after 95 days. The status of the readability check is shown in the media table.
- Repeat rate for readability check [times]: This option determines how many times the readability check will be performed. If you select Unlimited, the check will be performed with the set frequency and there will be no limit to the number of repetitions. If you select Execute and set the number of repetitions, the check will be repeated with the set frequency as many times as specified. For example, if you set the Readability check limit option to 90 days, and the Repeat rate for readability check [times] option to 3, the readability check will be performed every 90 days, for a total of 3 repetitions.
|The option Readability check limit determines the frequency of the check, while the option Repeat rate for readability check determines the number of times the check will be performed. The option Expiration of read check overdue determines how long after the frequency period has passed the readability check is considered overdue.|
Configuring readability check with a special media event
When you have configured the readability check options for a media pool, you can set up a schedule (or use existing schedule) and link a media event to it to perform the regular readability checks. For details, see Creating a Schedule.
- In the Main Selection -> Scheduling -> Schedules, select the schedule to which you want to link the event, select New and then New Media Event. A new media event is opened in which the tab Parameter is selected.
- Optionally, under the Sequence control, set up the Priority of your media event. SEPuler always executes the schedules with higher priority first. Default priority level is 1, which is the lowest priority (the highest is 99). The only exception are the schedules with priority 0, which override all other priorities and are always executed. For details, see Setting Event Priorities. You can also enable the Blocking date. This option should be used together with high priority for special events. If enabled, this event will block events of the same type with a lower priority, ensuring that the readability check is processed even if other readability checks are scheduled at the same time. For details, see Blocking Events.
- Under the Media action, select Readability check.
- Under the Parameter, specify the following options:
- Media Pool: Select a media pool for which you want to run a readability check, e.g., BCK_LTO_Archive.
- Drive: Optionally, select a drive which will be used for the check.
- Media: Optionally, select a specific tape media for the check. If no medium is selected, the action applies to all media in the selected media pool.
You can view the status of your readability check by selecting Job State -> Media Actions. Check the columns State and Action to verify the status of your readability check. For more details, double-click the relevant media action to open its properties. Under the Main Log tab the following information about performed readability check is displayed:
- Start and stop time of the readability check.
- On which device the medium was checked.
- The SEP sesam label of the medium.
- The last time the medium was initialized.
- The read throughput every minute.
- Information about the stored savesets on the medium.
- All segment marks of the tape.
- Readability check status (at the end of the log, e.g., success, error).
|As of 4.4.3 Beefalo V2, you can check the status and other details of your media actions online by using new Web UI. For details, see SEP sesam Web UI.|
Starting a readability check immediately
You can also start your readability check immediately under Activities -> Immediate Start -> Media Action, where you specify the media pool for which you want to run a readability check. SEP sesam checks and performs the readability checks that are due for the media in that pool.
Optionally, you can directly select a specific medium to check.