Summary of 4mm vs 8mm

From: Bridget (
Date: Wed Sep 19 1990 - 12:11:01 CDT

As promised here is a summary of replies I recieved to my request for commentaries on the differences between 8mm and 4mm tape devices.

First off, there is already an excellent summary out there that discusses most of this in a fair amount of detail:
        Subject: SUMMARY: Exabyte (8mm) versus DAT (4mm)
        Newsgroups: comp.misc,comp.sys.dec,alt.sys.sun
        Followup-To: comp.misc
        Summary: You pays your money and you takes your choice.
        Organization: Oak Ridge National Lab

For my 10 cents worth most of what I posted in my original query seems to check out. Here then are the most important points made by the 23 people that replied (thanks guys!).

        1. 8mm hold more than 4mm (2.3 vs 1.3 G).
        2. 8mm transfer data to tape faster (250K vs 180K altho for the 4mm this seems to depend on which driver you are using).
        3. 4mm give *MUCH* faster access (30 secs vs 30 mins for a rule of thumb).
        4. 8mm have been around longer and thus may be more reliable.
        5. There is more competition in the 4mm market and this is a good thing for the buyer (us!)
        5. 8mm tapes are cheaper than 4mm tapes ($10 vs $20 anecdotally)
Bottom line is:
        People who have 8mm and 4mm would buy 4mm in future (with one exception)
        People who have 8mm only don't seem to trust the 4mm and are looking to improvements in the 8mm to increase access time.
        People who use the device primarlily for backups don't care about the access time.
        People who use the device as an archive and retrieval system care passionately about the access time.
Commercial break:
        About a half dozen folks said that the company to talk to is Apunix
        (1-800-8-APUNIX) and highly recommended their service, software and
        expertise. I'm in no way affiliated with Apunix but as this sort of
        enthusiasm is so unusual I thought I'd pass it along.
So what did we do? We ordered a 4mm from Apunix a few days ago. The access time was just too important to us to give up for all the other advantages of the 8mm. Time will tell whether this was the right choice...

So thanks once again to the knowledgable sun-managers. This is a great list
in spite of the ~10 messages a day I wish I didn't get.

Bridget Carragher

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