UBI Used In Commercial Products ??

UBI Used In Commercial Products ??

[Johnson, Charles F]

Does anyone on this list know if UBI is currently being used in any
commercially released products ??
If so, does anyone know which ones ??

Charles Johnson
Ultra-Mobility Group
Platform Software Engineering
Intel Corporation
charles.f.johnson@intel.com

Re: UBI Used In Commercial Products ??

[Sergei Sharonov]

Hello,

> Does anyone on this list know if UBI is currently being used in any
> commercially released products ??
> If so, does anyone know which ones ??

I am probably missing something here, but how can UBI be useful by itself?
I would think until UBIFS is ready there is not much one can do with it.
Please tell me I am wrong ;-)

I am not aware of any non-commercial solution that can be used on a system
that:
1. Has lots (gigabytes) of flash
2. Must be power-fail safe.
3. Must boot in seconds even after power cycle
4. Does not have internal battery or super-capacitor to allow for sync on
power failure.

I hope UBI+UBIFS will be able to do that but it is not ready yet. Another
possibility is logfs but it is not ready either.

Sorry if that is a bit off-topic.

Regards,

Sergei Sharonov

RE: UBI Used In Commercial Products ??

[Johnson, Charles F]

JFFS2 has been modified to sit on top of UBI.  

One thought here is that I would think that mounting is a fairly rare
occurance.  
You're much more likely to coming back from suspend.  Notice the
difference in time it takes from my HP iPAQ to power-on normally vs a
cold boot.  It is very different.  


Charles Johnson
Ultra-Mobility Group
Platform Software Engineering
Intel Corporation
charles.f.johnson@intel.com


-----Original Message-----
From: linux-mtd-bounces@lists.infradead.org
[mailto:linux-mtd-bounces@lists.infradead.org] On Behalf Of Sergei
Sharonov
Sent: Wednesday, October 31, 2007 3:10 PM
To: linux-mtd@lists.infradead.org
Subject: Re: UBI Used In Commercial Products ??

Hello,

> Does anyone on this list know if UBI is currently being used in any
> commercially released products ??
> If so, does anyone know which ones ??

I am probably missing something here, but how can UBI be useful by
itself?
I would think until UBIFS is ready there is not much one can do with it.
Please tell me I am wrong ;-)

I am not aware of any non-commercial solution that can be used on a
system
that:
1. Has lots (gigabytes) of flash
2. Must be power-fail safe.
3. Must boot in seconds even after power cycle
4. Does not have internal battery or super-capacitor to allow for sync
on
power failure.

I hope UBI+UBIFS will be able to do that but it is not ready yet.
Another
possibility is logfs but it is not ready either.

Sorry if that is a bit off-topic.

Regards,

Sergei Sharonov





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Re: UBI Used In Commercial Products ??

[Sergei Sharonov]

Hi,
> JFFS2 has been modified to sit on top of UBI.

Yes, I know. Is that better then JFFS2 on top of mtdblock device?
  
> One thought here is that I would think that mounting is a fairly rare
> occurance.  
> You're much more likely to coming back from suspend.  Notice the
> difference in time it takes from my HP iPAQ to power-on normally vs a
> cold boot.  It is very different. 

Still one must plan for the worst case and the worst case for me
was about 2 hours of mount time after I used ftp to transfer large file.
I suspect ftp was writing really small jffs2 nodes.
Disclaimer: that was about 2 years ago and jffs2 might have improved,
processor (ARM9) was not a speed demon either.
If you do that on your iPAQ (create large file with lots of small nodes)
and then cold boot it - would you be willing to wait for an hour for it to 
become usable again?

I really hope UBI+UBIFS will overcome this problem. Still there is a concern 
here since UBI scales linearly. Can somebody plz post UBI scan time for large
flash array?

Regards,

Sergei Sharonov

Re: UBI Used In Commercial Products ??

[Jamie Lokier]

Sergei Sharonov wrote:
> 2 hours of mount time after I used ftp to transfer large file.

Wow!

> I really hope UBI+UBIFS will overcome this problem. Still there is a
> concern here since UBI scales linearly. Can somebody plz post UBI
> scan time for large flash array?

The only way to get sub-linear scaling is to designate a sub-linear
subset of eraseblocks which are read at scanning/mount time.

Doing that at the same time as wearing all eraseblocks equally is
quite tricky, and probably requires a phase tree and multi-headed
logging structure, like LogFS (I'm not sure if LogFS actually does
both, though).

Such a structure is not particularly simple, and will be present in
the best flash filesystems eventually.  So I wonder if UBI is really a
good place to have a second copy of those algorithms.

I like the idea of UBI, to abstract block allocation and wear tracking
from the filesystem, but it seems the sub-linear scan time requirement
is a tricky one to do without implementing a non-trivial
filesystem-like algorithm in UBI itself.

I'll be delighted to read that the problem's been solved, when it has
been solved, though :-)

-- Jamie

Re: UBI Used In Commercial Products ??

[Josh Boyer]

On Wed, 31 Oct 2007 23:01:07 +0000 (UTC)
Sergei Sharonov <sergei.sharonov@halliburton.com> wrote:

> Hi,
> > JFFS2 has been modified to sit on top of UBI.
> 
> Yes, I know. Is that better then JFFS2 on top of mtdblock device?

It depends.  If you have multiple partitions then yes, UBI is better.
It will wear-level across the entire root MTD device, whereas JFFS2 on
top of a partition will only wear-level within that partition.  UBI
also allows you to run other filesystems in different volumes, or have
static volumes.

If you have just a single JFFS2 filesystem that spans the whole flash
chip anyway, then maybe not.

josh

Re: UBI Used In Commercial Products ??

[David Woodhouse]

On Wed, 2007-10-31 at 23:01 +0000, Sergei Sharonov wrote:
> Disclaimer: that was about 2 years ago and jffs2 might have improved,
> processor (ARM9) was not a speed demon either.

The last two years would include all the optimisation work we've done
having started using JFFS2 on OLPC, with its 1GiB of NAND flash.

We're still pushing the limits of the JFFS2 design, at that size, but it
isn't as bad as it was.

-- 
dwmw2

Re: UBI Used In Commercial Products ??

[Jamie Lokier]

Johnson, Charles F wrote:
> One thought here is that I would think that mounting is a fairly rare
> occurance.  You're much more likely to coming back from suspend.

No, that only applies to portable devices like your iPAQ :-)

Sergei Sharonov wrote:
>> 4. Does not have internal battery or super-capacitor [...]

But even in some devices with batteries, mount time is a problem.  I
turn my phone off every night.  I don't want to receive any calls, and
I do want to conserve the battery charge.

It doesn't suspend, it powers off(*), and needs to remount everything
after booting in the morning.  The 20 seconds to boot the phone is
annoying, but acceptable.  Longer would be very annoying.

(*) I suspect suspend-to-RAM would be a problem with phones, because
(like my laptop), a suspended device consumes its battery charge much
more quickly than a device completely powered off.  Unless you suspend
to flash, that is :-)  Sometimes a phone is turned off to conserve
battery charge, so it really needs to do that.

-- Jamie