linux-kernel - Re: Linux UDF support

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Message-Id: <201408251524.05443@pali>
Date:	Mon, 25 Aug 2014 15:24:05 +0200
From:	Pali Rohár <pali.rohar@...il.com>
To:	Austin S Hemmelgarn <ahferroin7@...il.com>
Cc:	Jan Kara <jack@...e.cz>, linux-kernel@...r.kernel.org
Subject: Re: Linux UDF support

Hi,

On Monday 25 August 2014 14:45:13 Austin S Hemmelgarn wrote:
> On 2014-08-24 08:46, Pali Rohár wrote:
> > Hi,
> > 
> > I would like to know what is state of linux UDF driver. It
> > is experimental or is now suitable for storing data?
> 
> I know that read support works for every version I have
> tested, but I've only tested it reading data from DVD's and
> Blu-Ray discs, so I don't know how well it works for other
> purposes.
> 

Ok. I'm thinking about using UDF on HDD and usb flash disks (not 
on optical medium). And here I need write support too.

> > According to wikipedia [1] UDF has open specification format
> > and can be used also for HDDs (not only optical discs).
> > 
> > In OS support table is written that all major and other
> > minor OSs support UDF FS (without needs for additional
> > programs).
> > 
> > So it looks like UDF is good candidate for multi OS
> > filesystem. Are there any disadvantages for using UDF on
> > e.g USB flash disk? (when I want read/write support on
> > Linux, Windows 7 and Mac OS X)
> 
> If you are going to go that way, make sure to use the Spared
> Build, as otherwise you will run in to the same media
> wear-out issues that NTFS and FAT have.  Also, keep in mind
> that pre-Vista Windows and pre-10.4 OSX don't have very good
> support for the newer formats.
> 

What is Spared Build? And how to use it?

Problem with NTFS is that linux driver has write support marked 
as experimental. FAT has problems with big files and for exFAT 
there is no driver in linux kernel yet...

> > Because lot of manuals say that FAT32 (or NTFS) is only one
> > solution for using USB flash disk on more OS.
> > 
> > On wikipedia there is one note about linux: Write support is
> > only up to UDF version 2.01. Is this restriction still
> > valid?
> 
> I do know that we support reading UDF 2.60 (I've used linux to
> read Blu-Ray discs), but I have no idea about write support
> for versions above 2.01.
> 
> > What will happen if I try to mount FS with UDF version 2.60
> > in R/W mode on linux? It will fallback to R/O mode? Or
> > newly written files will be in previous (2.01) versions?
> > 
> > And last question: Is there some fsck tool for UDF? Or at
> > least tool which print if FS is in inconsistent state?
> 
> Most Linux distributions have a package called udftools, the
> upstream URL given by portage is
> http://sf.net/projects/linux-udf/
> 

That project does not have udf fsck tool :-(

> > [1] - http://en.wikipedia.org/wiki/Universal_Disk_Format

Ok, I will wait for response from maintainer Jan, he probably 
would know more...

-- 
Pali Rohár
pali.rohar@...il.com

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