Fwd: Re: OT: svscan and the hard disk

Fwd: Re: OT: svscan and the hard disk

[Martín Marqués]

Any thoughts on what DJB thinks of the Linux FS?

Sorry for him, each day I convince myself of not using Qmail ever!

Saludos... :-)

----------  Forwarded Message  ----------

Subject: Re: OT: svscan and the hard disk
Date: 30 Nov 2001 02:05:35 -0000
From: "D. J. Bernstein" <djb@cr.yp.to>
To: qmail@list.cr.yp.to

Pavel Kankovsky writes:
> all my attempts to find any piece of standard/specification/documentation
> saying that fs metadata are to be updated synchronously have failed so far

doc/smm/03.fsck_ffs/2.t

The guarantees provided by FFS make it reasonably easy for mail-handling
software to perform reliable disk transactions. The speed is adequate
for most sites.

The Linux filesystem designers, ignorant of the demands of critical
applications, screwed this up in two ways:

   * They broke compatibility, by failing to provide the FFS system
     calls with the FFS guarantees.

     They wanted an asynchronous rename(), for example. They should have
     added an asyncrename() system call. Instead they foolishly changed
     the semantics of rename(), breaking mail-handling programs.

     Of course, the incompatibility isn't obvious to people who don't
     realize that some programs rely on rename() being synchronous.

   * They didn't provide any way to perform reliable transactions, other
     than syncing the whole filesystem (with, e.g., a directory fsync).

     Even sync mode is worrisome. Has anyone verified that blocks are
     written to disk in the correct order? This is not rocket science,
     but it does require a certain level of care with every operation.

     Supposedly there's a faster transaction mechanism now, but I don't
     trust it. Do the people writing the filesystem code understand that
     there _is_ a correct order for block writes?

The situation since then has become even worse. Filesystem reliability
has gone down the tubes: users are regularly suffering data corruption,
even when there _isn't_ a crash. There are at least four different
filesystem transaction interfaces.

I'm reorganizing most of my create-one-file programs to use a generic
atomicwrite tool, so that all the stupid portability issues are isolated
inside one program. Meanwhile, qmail 2 uses its own internal filesystem
for the queue.

---Dan
n

-------------------------------------------------------

-- 
Porqué usar una base de datos relacional cualquiera,
si podés usar PostgreSQL?
-----------------------------------------------------------------
Martín Marqués                  |        mmarques@unl.edu.ar
Programador, Administrador, DBA |       Centro de Telematica
                       Universidad Nacional
                            del Litoral
-----------------------------------------------------------------

Re: Fwd: Re: OT: svscan and the hard disk

[José Luis Domingo López]

On Friday, 30 November 2001, at 09:33:21 -0300,
Martín Marqués wrote:

> Any thoughts on what DJB thinks of the Linux FS?
> 
> Sorry for him, each day I convince myself of not using Qmail ever!
> 
Does this means that the opinions of those who don't think like you
doesn't quality, or worth being taken into account ?.

How many times a week do you hear "subsystem X is broken", or "kernel
developer Y fucked this" on this list ?. Is this different from the same
facts, but being said by someone (DJB) who obviously has many people
against, for several reasons (many of them, non-technical ones) ?

PS: first and last email from my part on this subject.

-- 
José Luis Domingo López
Linux Registered User #189436     Debian Linux Woody (P166 64 MB RAM)
 
jdomingo EN internautas PUNTO org  => ¿ Spam ? Atente a las consecuencias
jdomingo AT internautas DOT   org  => Spam at your own risk

Re: Fwd: Re: OT: svscan and the hard disk

[Martín Marqués]

On Vie 30 Nov 2001 20:29, José Luis Domingo López wrote:
> On Friday, 30 November 2001, at 09:33:21 -0300,
>
> Martín Marqués wrote:
> > Any thoughts on what DJB thinks of the Linux FS?
> >
> > Sorry for him, each day I convince myself of not using Qmail ever!
>
> Does this means that the opinions of those who don't think like you
> doesn't quality, or worth being taken into account ?.
>
> How many times a week do you hear "subsystem X is broken", or "kernel
> developer Y fucked this" on this list ?. Is this different from the same
> facts, but being said by someone (DJB) who obviously has many people
> against, for several reasons (many of them, non-technical ones) ?
>
> PS: first and last email from my part on this subject.

Sorry. I think you missunderstood me. I am working on Postfix (see the 
headers of the mail), but we work alot with Qmail here.
I really never liked it that much (lots of things that just ich me alot), and 
I find myself happy with Postfix.
What I wanted was an opinion, just because lots of people are talking about 
data loses on some of the Journaling systems (especially reiser on IDE HD).

I hope nobody got offended, at least from my part. I totally disagree with 
the thoughts of DJB.

Once againg, sorry.

-- 
Porqué usar una base de datos relacional cualquiera,
si podés usar PostgreSQL?
-----------------------------------------------------------------
Martín Marqués                  |        mmarques@unl.edu.ar
Programador, Administrador, DBA |       Centro de Telematica
                       Universidad Nacional
                            del Litoral
-----------------------------------------------------------------

Re: Fwd: Re: OT: svscan and the hard disk

[H. Peter Anvin]

Followup to:  <20011201002956.A3050@dardhal.mired.net>
By author:    =?iso-8859-1?Q?Jos=E9_Luis_Domingo_L=F3pez?= 
	<jdomingo@internautas.org>
In newsgroup: linux.dev.kernel
>
> On Friday, 30 November 2001, at 09:33:21 -0300,
> Martín Marqués wrote:
> 
> > Any thoughts on what DJB thinks of the Linux FS?
> > 
> > Sorry for him, each day I convince myself of not using Qmail ever!
> > 
> Does this means that the opinions of those who don't think like you
> doesn't quality, or worth being taken into account ?.
> 
> How many times a week do you hear "subsystem X is broken", or "kernel
> developer Y fucked this" on this list ?. Is this different from the same
> facts, but being said by someone (DJB) who obviously has many people
> against, for several reasons (many of them, non-technical ones) ?
> 
> PS: first and last email from my part on this subject.
> 

The thing about it, is that he seems to be complaining about *HIS OWN*
bugs!  If he relies on system calls having semantics any other than
the one specified in the POSIX standard, his code is either
fundamentally broken, or he needs it very clearly documented.  He
seems to be relying on "well, BSD behaved this way in the past" and
then blames Linux when his assumptions fall apart.

	-hpa
-- 
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt	<amsp@zytor.com>