rollover

2 Articles

Patch, Or Your Solid State Drives Roll Over And Die

December 10, 2019 by 117 Comments

Expiration dates for computer drives? That’s what a line of HP solid-state drives are facing as the variable for their uptime counter is running out. When it does, the drive “expires” and, well, no more data storage for you!

There are a series of stages in the evolution of a software developer as they master their art, and one of those stages comes in understanding that while they may have a handle on the abstracted world presented by their development environment they perhaps haven’t considered the moments in which the real computer that lives behind it intrudes. Think of the first time you saw an SQL injection attack on a website, for example, or the moment you realised that a variable type is linked to the physical constraints of the number of memory locations it has reserved for it. So people who write software surround themselves with an armoury of things they watch out for as they code, and thus endeavour to produce software less likely to break. Firmly in that arena is the size of the variables you use and what will happen when that limit is reached.

Your Drive Is Good For About 3 Years And 9 Months

Sometimes though even developers that should know better get it wrong, and this week has brought an unfortunate example for the enterprise wing of the hardware giant HP. Their manufacturer has notified them that certain models of solid-state disk drives supplied in enterprise storage systems contain an unfortunate bug, in which they stop working after 32,768 hours of uptime. That’s a familiar number to anyone working with base-2 numbers and hints at a 16-bit signed integer in use to log the hours of uptime. When it rolls over the value will then be negative and, rather than the drive believing itself to be in a renewed flush of youth, it will instead stop working.

Egg on the faces of the storage company then, and an urgently-released patch. We suspect that if you own a stack of these drives you will already know about the issue and be nervously pacing the racks of your data centre.

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Countdown To The GPS Timepocalypse

April 5, 2019 by 75 Comments

There’s a bug about to hit older GPS hardware that has echos of Y2K. Those old enough to have experienced the transition from the 1990s to the 2000s will no doubt recall the dreaded “Year 2000 Bug” that was supposed to spell the doom of civilization. Thanks to short-sighted software engineering that only recorded two digits for year, we were told that date calculations would fail en masse in software that ran everything from the power grid to digital watches. Massive remediation efforts were undertaken, companies rehired programmers whose outdated skills were suddenly back in demand, and in the end, pretty much nothing actually happened.

Yet another epoch is upon us, far less well-known but potentially deeper and more insidious. On Saturday April 6, 2019 — that’s tomorrow — GPS receivers may suffer from software issues due to rollover of their time counters. This could result in anything from minor inconvenience to major confusion, with an outside chance of chaos. Some alarmists are even stating that they won’t fly this weekend, for fear of the consequences.

So what are the real potential consequences, and what’s the problem with GPS in the first place? Unsurprisingly, it all boils down to basic math.

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