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From: "Jörn Engel" <joern@wohnheim.fh-wedel.de>
To: "Gareth Bult (Encryptec)" <Gareth@Encryptec.net>
Cc: Linux MTD <linux-mtd@lists.infradead.org>
Subject: Re: JFFS2 mount time
Date: Tue, 21 Dec 2004 14:09:24 +0100	[thread overview]
Message-ID: <20041221130924.GB22636@wohnheim.fh-wedel.de> (raw)
In-Reply-To: <1103562748.10800.62.camel@squizzey.bult.co.uk>

On Mon, 20 December 2004 17:12:28 +0000, Gareth Bult (Encryptec) wrote:
> On Mon, 2004-12-20 at 10:34 -0600, Josh Boyer wrote:
> > Ok, that's why I said "most".  And if your El Cheapo hardware has built
> > in wear leveling, then doing wear leveling on top of that is always
> > questionable.  It might not make things worse, but it's probably not
> > very efficient.

Imo jffs2-style wear leveling is very efficient.  So efficient, it
doesn't really matter whether the hardware does the same or not.

Difference between no wear leveling and what jffs2 does is - at most -
1% additional writes on the jffs2 side.  That's not much.  Agreed, it
can actually cost latency, but from a life-time or overall performance
point of view, it doesn't really matter.

On the other hand, it gives you absolute condidence that your El
Cheapo hardware doesn't need to have anything it may or may not
promise to have.  No nasty surprised when you really don't need them.

> > Now if you have El Super Cheapo hardware that explicitly states you need
> > to do wear leveling, that's a different story ;).

Noone will state that.  It's not exactly good marketing.  You might
remember so interesting stories about what marketing promised and what
actually got delivered, no?

> In summary: lots of manufacturers seem to be quoting virtual / physical
> block mapping on the fly with integrated wear levelling ... (!)
> 
> So maybe wear levelling is out of date at filesystem level ?
> The techworld link to the M-Systems chips looks interesting ..
> 
> Can anyone with detailed flash experience comment ?

The endorsed features sound quite nice, agreed.  But I have still to
read a spec that convinces me.

Jörn

-- 
My second remark is that our intellectual powers are rather geared to
master static relations and that our powers to visualize processes
evolving in time are relatively poorly developed.
-- Edsger W. Dijkstra

  reply	other threads:[~2004-12-21 13:10 UTC|newest]

Thread overview: 113+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-12-15 23:19 JFFS2 mount time Gareth Bult (Encryptec)
2004-12-16  0:15 ` Josh Boyer
2004-12-16  1:02   ` Gareth Bult (Encryptec)
2004-12-16 12:53     ` Josh Boyer
2004-12-16 21:22       ` Gareth Bult (Encryptec)
2004-12-16 21:28         ` Josh Boyer
2004-12-16 21:47           ` Gareth Bult (Encryptec)
2004-12-17 12:54             ` Josh Boyer
2004-12-17 15:33               ` Gareth Bult (Encryptec)
2004-12-17 16:02                 ` Josh Boyer
2004-12-17 16:46                   ` Gareth Bult (Encryptec)
2004-12-17 17:08                     ` Artem B. Bityuckiy
2004-12-17 17:10                     ` Josh Boyer
2004-12-17 17:26                       ` Gareth Bult (Encryptec)
2004-12-17 17:35                         ` Josh Boyer
2004-12-17 18:09                           ` Gareth Bult (Encryptec)
2004-12-17 19:14                             ` jasmine
2004-12-17 20:55                               ` Gareth Bult (Encryptec)
2004-12-18 16:02                           ` Jörn Engel
2004-12-20 16:34                             ` Josh Boyer
2004-12-20 17:12                               ` Gareth Bult (Encryptec)
2004-12-21 13:09                                 ` Jörn Engel [this message]
2004-12-21 13:24                                   ` Gareth Bult (Encryptec)
2004-12-21 13:34                                     ` Jörn Engel
2004-12-18 16:19             ` Jörn Engel
2004-12-18 17:32               ` Gareth Bult (Encryptec)
2004-12-18 17:52                 ` Jörn Engel
2004-12-18 18:11                   ` Jörn Engel
2004-12-18 20:48                     ` Gareth Bult (Encryptec)
2004-12-19  2:44                       ` Jörn Engel
2004-12-21 13:30                       ` Jörn Engel
2004-12-21 13:39                         ` [PATCH 1/22] Add drivers/mtd/devices/blockmtd.c Jörn Engel
2004-12-21 13:41                           ` [PATCH 2/22] Add copyrights Jörn Engel
2004-12-21 13:42                             ` [PATCH 3/22] Remove read-only option Jörn Engel
2004-12-21 13:44                               ` [PATCH 4/22] Change init/exit functions Jörn Engel
2004-12-21 13:45                                 ` [PATCH 5/22] Remove gcc warnings Jörn Engel
2004-12-21 13:47                                   ` [PATCH 6/22] Remove debug macros Jörn Engel
2004-12-21 13:48                                     ` [PATCH 7/22] Lindent Jörn Engel
2004-12-21 13:49                                       ` [PATCH 8/22] Remove sync interface Jörn Engel
2004-12-21 13:51                                         ` [PATCH 9/22] Change parameter interface to phram-style Jörn Engel
2004-12-21 13:53                                           ` [PATCH 10/22] Cleanup macro usage Jörn Engel
2004-12-21 13:54                                             ` [PATCH 11/22] kfree simplifications Jörn Engel
2004-12-21 13:55                                               ` [PATCH 12/22] change blockmtd_sync Jörn Engel
2004-12-21 13:57                                                 ` [PATCH 13/22] remove erase regions Jörn Engel
2004-12-21 14:01                                                   ` [PATCH 14/22] Change add_device Jörn Engel
2004-12-21 14:02                                                     ` [PATCH 15/22] Rename unreadable mutex Jörn Engel
2004-12-21 14:03                                                       ` [PATCH 16/22] list changes Jörn Engel
2004-12-21 14:04                                                         ` [PATCH 17/22] Rename central struct Jörn Engel
2004-12-21 14:06                                                           ` [PATCH 18/22] Function renaming Jörn Engel
2004-12-21 14:09                                                             ` [PATCH 19/22] Fold various erase functions Jörn Engel
2004-12-21 14:10                                                               ` [PATCH 20/22] Fold various write functions Jörn Engel
2004-12-21 14:11                                                                 ` [PATCH 21/22] Default erase size Jörn Engel
2004-12-21 14:13                                                                   ` [PATCH 22/22] Readahead Jörn Engel
2004-12-21 18:42                                                   ` [PATCH 13/22] remove erase regions Christopher Hoover
2004-12-21 18:49                                                     ` Jörn Engel
2004-12-21 21:09                                                       ` Christopher Hoover
2004-12-22  2:47                                                         ` Eric W. Biederman
2004-12-22  8:59                                                           ` Jörn Engel
2004-12-22 10:05                                                             ` Eric W. Biederman
2004-12-22 10:41                                                               ` Jörn Engel
2004-12-21 13:42                           ` [PATCH 1/22] Add drivers/mtd/devices/blockmtd.c Gareth Bult (Encryptec)
2004-12-21 14:15                             ` Jörn Engel
2004-12-21 13:40                         ` JFFS2 mount time Gareth Bult (Encryptec)
2004-12-21 15:00                           ` David Woodhouse
     [not found]                             ` <1103644945.10792.175.camel@squizzey.bult.co.uk>
2004-12-21 16:04                               ` Jörn Engel
2004-12-16 13:43 ` Ferenc Havasi
2004-12-20 16:01   ` Gareth Bult (Encryptec)
2004-12-20 16:09     ` Ferenc Havasi
2004-12-20 16:39       ` Gareth Bult (Encryptec)
2004-12-20 17:48       ` Gareth Bult (Encryptec)
  -- strict thread matches above, loose matches on Subject: below --
2004-10-20 14:26 Ferenc Havasi
2004-10-20 15:26 ` [OBORONA-SPAM] " Artem B. Bityuckiy
2004-10-20 15:49   ` Ferenc Havasi
2004-10-20 15:53     ` Artem B. Bityuckiy
2004-10-21  6:29 ` Artem B. Bityuckiy
2004-10-21  6:54   ` Ferenc Havasi
2004-10-21  7:16     ` Artem B. Bityuckiy
2004-10-21 19:50       ` Ferenc Havasi
2004-10-21 12:49 ` Jarkko Lavinen
2004-10-21 19:11   ` Ferenc Havasi
2004-10-22  9:58   ` Ferenc Havasi
2004-10-21 13:24 ` David Woodhouse
2004-10-21 20:05   ` Ferenc Havasi
2004-10-22 12:44     ` Artem Bityuckiy
2004-10-25  9:36       ` Ferenc Havasi
2004-10-25 10:56         ` Artem Bityuckiy
2004-10-25 15:30           ` Ferenc Havasi
2004-10-26  9:59             ` Artem Bityuckiy
2004-10-26 10:21               ` Ferenc Havasi
2004-10-26 11:05                 ` Artem Bityuckiy
2004-10-26 13:52                   ` Ferenc Havasi
2004-10-25 11:21         ` Artem Bityuckiy
2004-10-26  9:29       ` Jarkko Lavinen
2004-10-26 10:24         ` Ferenc Havasi
2004-10-26 10:34         ` Artem Bityuckiy
2004-01-13 12:50 Jarkko Lavinen (NMP/Helsinki)
2004-01-13 13:19 ` Joakim Tjernlund
2004-01-13 13:39 ` David Woodhouse
2004-01-13 15:25   ` Kenneth Johansson
2004-01-13 15:30     ` David Woodhouse
2004-01-13 16:21       ` Kenneth Johansson
2004-01-13 17:29         ` Jörn Engel
2004-01-13 17:40           ` Kenneth Johansson
2004-01-13 18:43             ` Jörn Engel
2005-01-04 15:00 ` Steven Scholz
2005-01-05 10:45   ` Artem B. Bityuckiy
2005-01-05 11:10     ` Ferenc Havasi
2005-01-05 11:24       ` Steven Scholz
2005-01-05 11:45         ` Artem B. Bityuckiy
2005-01-06 10:50           ` Ferenc Havasi
2005-01-10 15:14           ` Steven Scholz
2005-01-10 15:25             ` Steven Scholz
2005-01-11  8:26             ` Ferenc Havasi
2005-01-11  8:34               ` Steven Scholz

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