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Subject: Re: UBI/ubifs problem
From: Artem Bityutskiy <dedekind1@gmail.com>
To: Ricard Wanderlof <ricard.wanderlof@axis.com>
Date: Fri, 09 Mar 2012 15:51:24 +0200
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On Fri, 2012-03-09 at 14:45 +0100, Ricard Wanderlof wrote:
> On Fri, 9 Mar 2012, Artem Bityutskiy wrote:
> 
> >> I think what I'm thinking about is that in the specialized case of ubifs
> >> used for a read-only file system, such as a root file system (without
> >> /etc, /var, and so on), it would be possible for mkfs.ubifs to create a
> >> file system, and use as many LEBs as it needs for the actual data. On a
> >> read-only file system there doesn't even have to be a journal, although I
> >> don't know if that is possible.
> >
> > Well, I'd accept a patch which added a --optimize-for-ro option which
> > would prepare a file-system with the smallest journal size.
> 
> Can the journal be eliminated completely or does something in ubifs 
> require there to be a journal at all times, albeit small?

I think currently at least 5 LEBs are required:

/* Minimum number of logical eraseblocks in the log */
#define UBIFS_MIN_LOG_LEBS 2
/* Minimum number of bud logical eraseblocks (one for each head) */
#define UBIFS_MIN_BUD_LEBS 3
/* Minimum number of journal logical eraseblocks */
#define UBIFS_MIN_JNL_LEBS (UBIFS_MIN_LOG_LEBS + UBIFS_MIN_BUD_LEBS)

-- 
Best Regards,
Artem Bityutskiy