The IT number of the Beast – doubled!

http://en.wikipedia.org/wiki/M-497_Black_Beetle

Experimental jet-powered locomotive test bed

Last year I blogged about 497 being the IT number of the beast.

Why 497?

Because if a product uses a 32 bit counter to record uptime, and that counter records a tick every 10 msec, then that 32-bit counter will overflow after approximately 497.1 days.  This is because a 32 bit counter equates to 2^32, which equals 4,294,967,296 ticks.  If a tick is counted every 10 msec, we create 8,640,000 ticks per day (100*60*60*24).  So after 497.102696 days, the counter will overflow.   What happens next depends on good programming:  normally the counter just starts again, but worst case a function might stop working or the product might even reboot.

Fortunately we are seeing less and less of these issues but just occasionally one still slips  out.  Recently IBM released details of a 994 day reboot bug in the ESM code of some of their older disk enclosures (EXP100, EXP700 and EXP710).   Details about this bug can be found here.  What I find interesting is the number of days it takes to occur, since 994 is actually 497 times two.  This suggests that this product records a tick every 20 msec.  This meant we got past 497 days without an issue but hit a problem after exactly double that number.   So if you still have these older storage enclosures, you will need to reboot the ESMs (after checking the alert).

I googled 497 to see what images that number brings up and was amazed to find the M-497  jet powered train.   More details on this rather interesting attempt at speeding up the commute home can be found here and here.   It adds a whole new meaning to keeping behind the yellow line.

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About Anthony Vandewerdt

I am an IT Professional who lives and works in Melbourne Australia. This blog is totally my own work. It does not represent the views of any corporation. Constructive and useful comments are very very welcome.
This entry was posted in Brocade, Cisco, IBM Storage and tagged , , , , , , . Bookmark the permalink.

7 Responses to The IT number of the Beast – doubled!

  1. Pingback: The IT number of the Beast – doubled! « Storage CH Blog

  2. MrOdysseus says:

    Hi Anthony, Awesome Train..

    I had to chuckle when you used the term “old”, since our “new” XIV’s suffer from a 208 day bug. Not sure if it is related to a similar counter.

    SYS-207655
    Linux kernel issue resulting in a module hang/failure if the module has been
    powered on for 208 days. It is likely that multiple modules would fail if all
    modules had identical up-time of 208 days.
    Severity
    Hyper

  3. Bharath Gowda says:

    Hello MrOdysseus and Anthony,

    Can you give more information about XIV 208 days bug. Is this an issue with all XIV models or a specific model?

    Thanks in advance.

    Bharath

    • Hi Bharath,

      The XIV Gen3 on version 11.0 code has the same 208 day issue.
      It is fixed in 11.1 code.

      XIV Gen2 (which run 10.x code) is totally unaffected and has never had this issue.

      Every affected Gen3 client has been contacted and the issue remediated.

  4. cs says:

    XIV gen 2 is fixed is 10.2.4e-5 level.

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