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From: Jamie Lokier <jamie@shareable.org>
To: Artem Bityutskiy <dedekind@infradead.org>
Cc: "Adam S. Turowski" <a.turowski@wb.com.pl>,
	"linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>,
	Adrian Hunter <ext-adrian.hunter@nokia.com>
Subject: Re: [UBIFS] Filesystem capacity
Date: Tue, 17 Feb 2009 09:16:33 +0000	[thread overview]
Message-ID: <20090217091633.GB26354@shareable.org> (raw)
In-Reply-To: <1234857466.17790.227.camel@localhost.localdomain>

Artem Bityutskiy wrote:
> OK, then indeed Adrian wrote exactly the right thing. You have huge
> 4144-byte uncompressible nodes. You fit 3 of them to each eraseblock,
> and you waste 3440 bytes in each eraseblock. JFFS2 would jam a little
> more data, because it can split big blocks on parts.
> 
> In real life you will likely have compressible data, and many small
> files, so you will have small data nodes and many inode nodes, which
> are 160 bytes in size, so you will fit more.

Also, in real life, JFFS2 will behave badly when the filesystem is
completely full.  Its garbage collector can use 100% CPU for minutes
even on a small NOR flash, if the filesystem fills up too much.  It
happens because it's difficult to reorganise the data when there's no
spare room.

I wonder if the "lost" space in UBIFS is helpful to prevent long
garbage collection cycles?

-- Jamie

  reply	other threads:[~2009-02-17  9:17 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-02-16 14:44 [UBIFS] Filesystem capacity Adam S. Turowski
2009-02-16 15:54 ` Adrian Hunter
2009-02-17  0:39   ` Jamie Lokier
2009-02-17  6:11     ` Artem Bityutskiy
2009-02-17  8:01     ` Artem Bityutskiy
2009-02-17  6:07   ` Artem Bityutskiy
2009-02-17  7:39     ` Adam S. Turowski
2009-02-17  7:57       ` Artem Bityutskiy
2009-02-17  9:16         ` Jamie Lokier [this message]
2009-02-17  9:31           ` Artem Bityutskiy

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