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Comment by codezero | Hacker News Reader

  The latest work has been adding live update, making it possible to upgrade 
  to a new version of the operating system WITHOUT a reboot and without running
  processes even noticing. No other operating system can
  do this.

Can anyone correct me if I'm wrong – but can't Linux do this with Ksplice, and the more recent live kernel patching by Red Hat?

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An AIX admin claimed it could do a live update of even kernel code without a reboot. The solution for most others is clustering, needed to deal with hardware risk anyway. OpenVMS clusters have reportedly gone 20+ years without system downtime. Individual instances needed reboots so little that admins occasionally forgot how to do that. So, yes, there's precedents in other operating systems according to their users.

Note: And as far as OpenVMS, I believe it because those designers built it like their job depended on it not failing. A cluster of that OS shouldn't experience any significant downtime given about everything I've ever read on it.

We had 11 years of uptime on a VAX cluster at a company I worked for in the late 1990s.

They took it down in 2001 to replace it with something that took up 2U of rack space, about 2kw less power and ran windows 2000.

I turned up in 2012 to replace it again with something cloudy and it had 11 years of uptime (well done NT!) again[1] so YMMV.

The cloud based version has gone down about 10 times (thanks Azure!).

[1] not a great position but this was on an isolated network with locked down everything so less of a problem than a normally networked system.

That's funny. I swear I've considered just buying up a boatload of used Alpha and Itanium machines to keep a VMS cluster going another decade. Put a guard in front of it to block any attacks due to its age or protocols. People might laugh but my stuff would stay running no matter what. Example below:

http://h71000.www7.hp.com/openvms/brochures/commerzbank/comm...

Notice how the Intel hardware all failed when things heated up a bit. The AlphaServers running VMS just kept chugging along. The eventual fail-over didn't loose a single transaction. Aggravates me that I can't easily obtain such reliable IT hardware/software anymore outside eBay. I mean, HP NonStop sure as hell doesn't have a hobbyist program with used servers for $130. ;)

The mid-range HP stuff is pretty reliable. We had a DL380p Gen7 survive the switch underneath it catching fire. Had zero chassis failures on about 500 nodes in the last 12 years as well. Lose disks and power supplies all the time and the odd Ethernet interface but nothing else.

Agree with ebay. I still look around for Sun Ultra kit now and then but the wife has other ideas because it's noisy and expensive to run.

Wow! That is impressive. I appreciate the tip on those.

" I still look around for Sun Ultra kit now and then but the wife has other ideas because it's noisy and expensive to run."

The battle that never goes away. Haha. This is why you need a basement or soundproofed room for that stuff. That's on my todo list for next house.

The video can correct you. Watch it.

> MUCH BETTER THAN KSPLICE

> KSPLICE can handle only small security patches

> KSPLICE patches the running process

> Over time, crud accumulates in the process

> If the update fails, there is no recovery

https://youtu.be/0pebP891V0c?t=47m56s

Yes, and there are some cases when it works. I would not run our production system with Ksplice. The microkernel architecture makes it possible to restart kernel functionality seamlessly. Emphasis on restart. Ksplice just binary patches the running kernel and overwriting the changed parts. Very different scenario.

The talk addresses Ksplice specifically, noting that unlike the MINIX mechanism, it doesn't handle significant changes to data structures well.

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