[TUHS] The evolution of Unix facilities and architecture
Larry McVoy
lm at mcvoy.com
Fri May 12 10:21:12 AEST 2017
Yeah, I get ordered writes, I taught a CS course at Stanford and I made
my students learn all about them. I'm a UFS guy, so far as I know I'm
the last guy to push UFS/FFS forward (which is sort of sad).
The Linux stuff is better. It just is. And we should all respect that,
I know we sit around and love on ancient Unix, and believe me, I love
that stuff it changed the world, but we should respect people who have
moved it past what Unix did. And I think Linux moved the file system
past what Unix did.
--lm
On Thu, May 11, 2017 at 07:48:27PM -0400, Ron Natalie wrote:
> Ordered writes go back to the original BSD fast file system, no? I seem
> to recall that when we switched from our V6/V7 disks,
> the filesystem got a lot more stable in crashes.
>
> -----Original Message-----
> From: TUHS [mailto:tuhs-bounces at minnie.tuhs.org] On Behalf Of Dave Horsfall
> Sent: Thursday, May 11, 2017 7:47 PM
> To: The Eunuchs Hysterical Society
> Subject: Re: [TUHS] The evolution of Unix facilities and architecture
>
> On Thu, 11 May 2017, Larry McVoy wrote:
>
> [...]
>
> > Try the same thing with Linux. The file system will come back,
> > starting with, I believe, ext2.
>
> That's a journalled FS, isn't it? In which case the transactions get
> replayed.
>
> > My belief is that Linux orders writes such that while you may lose
> > data (as in, a process created a file, the OS said it was OK, but that
> > file will not be in the file system after a crash), but the rest of
> > the file system will be consistent. I think it's as if you powered
> > off the machine a few seconds earlier than you actually did, some
> > stuff is in flight and until they can write stuff out in the proper
> > order you may lose data on a hard reset.
>
> And FreeBSD (at least) has been doing ordered writes for quite some time.
>
> --
> Dave Horsfall DTM (VK2KFU) "Those who don't understand security will
> suffer."
--
---
Larry McVoy lm at mcvoy.com http://www.mcvoy.com/lm
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