Sunday, January 30, 2011

Watershed events in systems software: IPv6, 4K sectors

It's looking like 2011 will be a watershed year for low-level system software wonks, as we will be seeing some major transitions in some core software behaviors that have been around for decades. Here's a couple that I've been following:

  • The IPv4 to IPv6 transition is fully here, as the IPv4 countdown clock now says that we now have just two days until IANA IPv4 address exhaustion, and just over 6 months until regional registry exhaustion. The Internet Society is trying to organize World IPv6 day for June, and various carriers and ISPs are working through their IPv6 transition plans -- here's an example. Behind the scenes, it's a blizzard of technologies and acronyms, enough to leave even the most avid networking enthusiast bewildered. Of one thing you may be sure: it's going to be an opportunity to upgrade your gear.

  • Another transition which isn't getting quite so much press, but which will also affect us systems sorts, is the storage systems transition from 512-byte sectors to 4096-byte sectors. The new drives, called "Advanced Format" drives, bring both capacity and efficiency gains, but will require careful attention by those who implement file systems, database systems, and the like. One particular bit of complexity is the transition mode on some of these drives, called "512e" mode, which involves the use of emulation firmware that makes a 4K Advanced Format drive appear to be operating as a old school 512-byte sector device. As some people have observed, this is very tricky stuff, and if not done exactly right could introduce some extremely mysterious failure modes. The good news is that there are lots of tools and information about Advanced Format drives available.

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