[TUHS] The evolution of Unix facilities and architecture

Ron Natalie ron at ronnatalie.com
Fri May 12 09:48:27 AEST 2017


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."



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