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If you are having problems with MirriM, first check the download page to make sure you have the latest version. Then check the FAQ below to make sure your question is not already answered. If you still have a problem or have any comments, or suggestions for future versions of MirriM then please contact us.


  1. Won't it take ages to synchronize large files over the Internet?
    MirriM only needs to send the parts of a file which have changed, not the whole file. So if, say, you have just added a couple of entries to a huge database, it won't need to transmit all the data. In fact it can reuse data from the out-of-date file even if it is no longer in the right order! This makes it very much faster than a naÔve copy of the whole file.
    Of course, if the file is completely different and you have a slow Internet connection, copying a large quantity of data will be slow. You can always ask MirriM not to copy a particular file at this time, and synchronize it later instead.
  2. Isn't copying files over the Internet really insecure?
    Our algorithms incorporate both encryption and compression, and in addition only transmitting the bits of data which have changed makes it much less likely that someone could intercept your files in a usable form.
  3. I'm going to the US, won't MirriM get confused about files created in different time zones?
    No, MirriM's algorithm is based on a universal time stamp (UTC) which is independent of time zones.
  4. New programs make me nervous, especially when they might alter or delete important files! How can I be sure I've set MirriM up right?
    We understand how you feel. However, since we use MirriM ourselves we are confident you won't lose anything you shouldn't. In fact MirriM has five separate features which help you ensure that your data is safe:
    1. Preview Changes. You can see exactly what MirriM is going to do before it makes any changes to any file, and can cancel the whole operation, remove any file from the synchronization, or change which copy of the file is used as the master.
    2. Dummy Run. MirriM goes through all the synchronization operations except for actually altering any of the files, so you can have a detailed look at the log file before deciding whether to do the synchronization for real.
    3. Prompts option. You can set MirriM to prompt you before it deletes a file, or in two-way mode to ask you which of two changed files to keep.
    4. Archive option. MirriM can archive every changed or deleted file for you, and you can specify how many versions to keep.
    5. Safety mode. MirriM will only copy files to a directory with BACKUP in the name if this option is set.
  5. Do I have to tell everyone who synchronizes their laptop with this office machine to exclude the new directory I've made?
    No, all you have to do is create a single empty file with a particular name in the directory and synchronizing machines will simply ignore it.
  6. I've deleted a bunch of files I no longer use from my laptop. Will MirriM just put them all back the next time I do a synchronization with a machine which still has them?
    Not in two-way mode. MirriM knows the difference between a file which still exists on machine A but has been deleted from machine B, and a newly created file on machine A. You can even delete them from machine A should you want to.
  7. I'm new to working with the command line version. Is there an easy way to set up automatic synchronization without having to write a complicated control file?
    Yes, you can use the interactive version of MirriM to set all the options you require, do a dummy run to check you got it right, then save to a control file which the command line version of MirriM can use.
  8. My computer is behind a firewall, can I still use MirriM to synchronize over the Internet?
    Yes, you just need to set your firewall to open/forward the port number that you are using with MirriM. The default port number that MirriM uses is 5331.
  9. Can I synchronize my office machine with my laptop while I'm away, so my coworkers can use the work I've been doing before I get home?
    Yes, provided you have Internet access, know the IP address of your office machine, and your laptop has sufficient privileges to connect with it.
  10. What if lots of people all need to synchronize with the same computer?
    This is perfectly possible, the MirriM service can carry out multiple synchronizations at the same time. You will need to make sure you have thought through who is allowed to change shared files on the server machine - obviously if 20 people all have permission to overwrite the same file you will have the same problems using MirriM as you would if they did it manually.


You can email us at support@mirrim.co.uk.

If you are reporting a problem, please try and give as detailed an explanation as possible so we can try and reproduce it.

Other contact details are:

Polyhedron Software Ltd.
Linden House
93 High Street
OX29 7RH

Tel: +44 (0)1865 300579
Fax: +44 (0)1865 300232

MirriM is created by Polyhedron logoPolyhedron Software Ltd.