автор
rr[N]


Add data recovery record. Optionally, redundant information
(recovery record) may be added to an archive. This will cause
a small increase of the archive size and helps to recover
archived files in case of floppy disk failure or data losses of
any other kind. A recovery record contains up to 524288 recovery
sectors. The number of sectors may be specified directly in the
'rr' command (N = 1, 2 .. 524288) or, if it is not specified by
the user, it will be selected automatically according to the
archive size: a size of the recovery information will be about
1% of the total archive size, usually allowing the recovery of
up to 0.6% of the total archive size of continuously damaged data.

It is also possible to specify the recovery record size in
percent to the archive size. Just append the percent character
to the command parameter. For example:

rar rr3% arcname

Note that if you run this command from .bat or .cmd file,
you need to use rr3%% instead of rr3%, because the command
processor treats the single '%' character as the start of
a batch file parameter. You may also use 'p' instead of '%',
so 'rr3p' will work too.

If data is damaged continuously, then each rr-sector helps to
recover 512 bytes of damaged information. This value may be
lower in cases of multiple damage.

The size of the recovery record may be approximately determined
by the formula <archive size>/256 + <number of recovery
sectors>*512 bytes.

ЖореГОгромное спасибо!
другой раз не ленись, достаточно глянуть в папку винрара и пошарить глазами ;-) - тут же увидишь файлик Rar.txt, который люди для кого-то писали, старались. Опять же консольная версия rar.exe выдают всю инфу нагора, правда не так подробно как rar.txt