Q202 - Unable to reliably calculate CRC


Your backup will work properly, but there is a high chance of timeout errors with large files.

You have selected to use the ZIP archive format. Akeeba Backup / Akeeba Solo may be unable to reliably calculate the CRC checksums under some circumstances:

  • The "hash" PHP extension is not present or activated in your php.ini

  • The functionality of the "hash" PHP extension is blocked by your host

Under these circumstances, a seemingly broken ZIP archive can be produced by Akeeba Backup. The archive is not really corrupt. The ZIP format requires us to store a "signature" for each file. Calculating this signature on large files without the "hash" extension is impossible, therefore this "signature" is empty. Archiver applications pick up this empty "signature" and think that the archive is broken, as the empty "signature" violates the ZIP format.

Depending on the source of the problem, you can try several workarounds:

  • Ask your host to make sure that the PHP "hash" extension is available and enabled on your site. They should also make sure that its functionality is not otherwise blocked, e.g. by disabled_functions.

  • Use the JPA archive format, which is much more efficient during archiving and extraction.