[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.


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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