How to Recover PAX Data Backup from an LTO Tape?

The pax backup (archive) utility is generally used in UNIX/AIX environments for managing data archives on magnetic tapes and other storage media. But sometimes, when you try to read an archive from an LTO tape cartridge, it becomes inaccessible for several reasons (discussed further). In such a case, you can recover your pax backup using Stellar Data Recovery for Tape Toolkit - a powerful LTO tape data recovery software that safely recovers your tape data on a Windows PC without any challenges. Let's read more.

What is PAX Command?

pax or Portable Archive Interchange  is a POSIX-defined archive format that is used for archiving data on LTO tape cartridges. You can create PAX data archives on UNIX, UNIX-like Operating Systems, and POSIX-compliant OS, like FreeBSD and CentOS, via Terminal and using the PAX utility. This utility is capable of reading, writing, and extracting data from tar, cpio, and ustar backup archives.

The pax command can be used for taking actions – List, Read, Write, and Copy – that depend on the presence of the -r and -w flags. These actions are called the 'modes' and work with a combination of -r (Read) and -w (Write). Tabulated below is the description of each mode:

You can use this command via the Terminal on a supported system along with additional options for extended functionalities, such as appending the data to the end of the archive, preventing overwriting of data, etc. Here is the syntax of the pax command:

Syntax – pax [Mode of Operation] [options] [filename]....

Here:

• Mode of Operation: none, Read (-r), Write (-w), or Copy (-r -w)
• Options: Additional options like -a, -b blocksize, -c, and more.

You can read more about the pax utility on its man page.

What is the Structure of pax Data Backup Stored on LTO Tapes?

PAX utility follows a defined structure to store files and folders sequentially on an LTO tape. The structure of the pax archive produced in -x pax format (cpio, pax, ustar, or xustar) is divided into one or more blocks that represent member files. The length of each block is 512 bytes.

Every pax archive file stored on the tape has this structure:

• Optional header block – It contains extended header records attributes, like length keyword, charset, comment, linkpath, etc.,  which are not allowed in the USTAR header.
• Header block – It stores information like name, mode, uid, etc., which describes the file. This information is stored in the ASCII format. This makes pax archives portable to different environments.
• Zero or more blocks – Next are the zeros or subsequent data blocks that store the contents of the file.

At the end of the archive are the two 512-byte blocks, which contain binary zeros. These two blocks mark the end of the archive on the tape. Moreover, any unused space in the header is also marked as binary zeros.

Here is a schematic of the PAX backup archive:

Why do pax Archives become Inaccessible on an LTO Tape?

Sometimes, you are unable to read or extract the PAX backup stored on a tape cartridge. This could happen for innumerable reasons. Some of these are listed below:

• Syntax error
• Incorrect attributes or file path mentioned in the command
• Faulty or incompatible tape drive
• Backup utility fails to recognize the tape cartridge
• Infinite loop errors while traversing a previously visited directory that is an ancestor (higher-level folder) of the last file visited
• Excessively long pathname causes the PAX utility to skip files/archives
• Incorrect -x pax format selected
• Trying to access an archive in an incompatible environment (Windows 10/11)

How to Recover PAX Backup from an LTO Tape Using Tape Data Recovery Software?

If you are unable to access or read the pax archive from an LTO tape using the -r or -r -w modes, you will require a dedicated LTO tape data recovery software like Stellar Data Recover for Tape Toolkit. This specialized software leverages its advanced algorithms to quickly scan the magnetic cartridge and create an image dump (.tape) of the recoverable data on the system's storage drive.

With this advanced software, you can easily recover data archives from magnetic tapes with missing or deleted catalog files in no time. However, the best use case of this powerful tape data recovery software is that you can use it for tapes that are nearing the end of their life cycle. You can create an image of the LTO tape and use it to retrieve data without putting undue strain on the physical media.

Here are some highlights of Stellar Data Recovery for Tape Toolkit:

• Pay-per-use subscription plan; 1 tape = 1 license
• Recovers backups and archives data from LTO tapes with 100% precision
• Creates an image dump (.tape) of the tape backup and scans it for recovering files
• Use the 'Auto' block size option to choose the predefined block size
• Selective recovery of individual files/folders from the tape dump image
• Retrieves all types of data – documents, images, videos, database files (SQL/MySQL), mailbox files (MBOX, OST, PST), etc.
• Recovers data from all the generations of Ultrium tape - from LTO-1 to LTO-9
• Compatible with a wide range of tape parsers – PAX (CentOS and FreeBSD), TAR, CPIO, ArGest (BRU), Arcserve, Symantec and Symantec Compressed Backup, Sun Solaris, etc.
• Supports LTO tapes of prominent brands – Overland-Tandberg, Fujitsu, IBM, Spectra Logic, HPE, Quantum, Dell EMC, and more

Now, let’s see how to perform pax archive data recovery using Stellar Data Recovery for Tape Toolkit.

• Open Stellar Data Recovery for Tape's official page. Click on Buy Now.

• Select the Toolkit edition and use the given dropdown list against the Number of Tape Supported to select the number of tape licenses you require. Again, click on Buy Now.

• After purchasing the tool and the required number of licenses, install it on a Windows/Windows Server OS.
• Next, connect the tape drive to the Windows PC using an SAS/HBA card, Thunderbolt, USB (in rare cases), or Ethernet.
• After connecting the tape drive, check Device Manager (Press WIN+X and then press M to open it). It should appear under ‘Tape drives.’
• After this, insert the tape cartridge containing the PAX backup archive into the tape drive.
• Now, launch Stellar Data Recovery for Tape Toolkit installed on your device.
• The Select Option screen will appear. Click on Create Image and then click on Next.

• The Select Destination Path screen will appear. Click on Browse to choose the path where you wish to save the tape drive image (.tape).
• Then, select ‘Auto‘ from the dropdown in the Block Size field. This will select the pre-defined block size and ensure faster processing and image creation.
• Click on Create. The software will begin creating the tape drive image. Wait for it to complete.

• After the image is successfully created, it will show the Image Created screen.
• Click on Scan to begin scanning the image for
• After finishing the scan, the software will display all the recoverable files. Select a file to preview it.
• Select the files you want to save and click on Save in the ribbon.
• The Save dialog box will appear. Choose either the Default Path (selected by the software) or the User Defined Path to save the data.

• After selecting the destination path, click on Save. The software will start saving the data at the selected location.
• After the software saves the recovered data, it will show the Process Complete dialog box. Click on OK to complete the process.

The recovered pax backup files will be saved at the selected destination.

In case you have already scanned your tape cartridge and have created the image dump (.tape) on your system, you can load it into the software to scan. Here's what to do:

• After launching the software, click on Load Image to load the tape dump. Click Next.

• Browse for the tape dump image you’ve just created and click on Next.

• After selecting the image, click on Scan.

Here is a detailed video about this advanced software.

Conclusion

There are several issues, as discussed above, that could make the data backup or an archive in an LTO tape inaccessible even with the original backup parser (program).

So, if you want to recover PAX data backup from an LTO tape, the most appropriate way is to use Stellar Data Recovery for Tape Toolkit. It is a powerful LTO tape data recovery software that uses powerful algorithms to scan and recover PAX archives stored on magnetic tape cartridges with 100% accuracy. It can also recover tape backups from tapes of all generations (LTO-1 to LTO-9) and supports magnetic tapes of popular brands, such as Quantum, HPE, IBM, Oracle, etc.

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