Usage of Ext4 in Android

[Janakiram Sistla]

Hi All,

Ext4 has been in kernel for quiet a long time for now.Is there any
dependency of using EXT4 for android kernel.Has anybody tried using
this in Android build.

Any inputs on using EXT4 in Android is much appreciated.

Regards,
Ram.

[Pavan Savoy]

any reasons why android should be moving away from yaffs2 to ext4?
I always thought ext2/3/4 sort of file-systems aren't good enough for embedded systems with NAND/eMMC sort of storages....

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[Janakiram Sistla]

On Mon, Sep 27, 2010 at 2:13 PM, Pavan Savoy <pavan...@gmail.com> wrote:
> any reasons why android should be moving away from yaffs2 to ext4?
> I always thought ext2/3/4 sort of file-systems aren't good enough for
> embedded systems with NAND/eMMC sort of storages....

So do you think that we cant use ext2 or ext3 ??

[Pavan Savoy]

Haven't we all been using ext3 or ext2 on our development platforms for like ever since android started ?
Was your question as to why android prefers not to use ext3/2/4 or what's stopping you from using ext2/3/4?

See no matter what we use in our daily environment and setups.. the android products which have come out have been yaffs2!!! (if you didn't know this before...)

and so, if you want to use ext4 ... for your hacked android phone .. or your development platform .. go ahead and use .. it - it's just linux kernel and file -system anyway ... there is nothing android dependent AFAIK ...

someone else can correct me on this ....

[The Dixter]

I think you will find more and more products use eMMC, which theoretically is more reliable, as the hardware handles bad blocks on its own.  Therefore, ext3 and ext4 become more practical and reasonable to use.  Yes yaffs2 seemed to be dominant in the last few years.  I think you will see a shift away from this.

[Janakiram Sistla]

On Mon, Sep 27, 2010 at 4:13 PM, The Dixter <thedi...@gmail.com> wrote:
> I think you will find more and more products use eMMC, which theoretically
> is more reliable, as the hardware handles bad blocks on its own.  Therefore,
> ext3 and ext4 become more practical and reasonable to use.  Yes yaffs2
> seemed to be dominant in the last few years.  I think you will see a shift
> away from this.

Yes Dixter.you are correct.I am thinking in the same context

[Disconnect]

You're forgetting Samsung and their proprietary (brain damaged) RFS.

(The fs may or may not be brain damaged. The version that shipped on the initial run of galaxy s devices is thoroughly broken - any concurrent IO causes it to crawl. So bad that the 'fix' was to move contacts db and the various carrier app storage to a completely different flash device.. Reports are mixed on the leaked froyo builds, but it might be getting better. It certainly couldn't be getting worse..)

Lots of people are using ext2 to fix that problem - create an ext2 loopback mount on the RFS partition and use that for /data instead..

[Seth Forshee]

On Mon, Sep 27, 2010 at 04:13:50PM -0700, The Dixter wrote:
> I think you will find more and more products use eMMC, which theoretically
> is more reliable, as the hardware handles bad blocks on its own. Therefore,

eMMC is based on MLC NAND, which at the hardware level is less reliable
than the SLC NAND being used with yaffs2. Any improved reliability would
come from the algorithms these chips are using internally to manage the
flash, and since we can't see those algorithms it's pretty difficult to
say which will be more reliable. Filesystems designed for HDDs may have
access patterns that accelerate wear on the flash as compared to
designed-for-flash filesystems as well.

The numbers I've seen do show yaffs2 on SLC performing better than
the ext family of filesystems on eMMC however.

> ext3 and ext4 become more practical and reasonable to use. Yes yaffs2
> seemed to be dominant in the last few years. I think you will see a shift
> away from this.

I think that's true, but it probably has as much to do with cost as
anything.

[Janakiram Sistla]

On Tue, Sep 28, 2010 at 9:22 AM, Seth Forshee <seth.f...@gmail.com> wrote:
> On Mon, Sep 27, 2010 at 04:13:50PM -0700, The Dixter wrote:
>> I think you will find more and more products use eMMC, which theoretically
>> is more reliable, as the hardware handles bad blocks on its own.  Therefore,
>
> eMMC is based on MLC NAND, which at the hardware level is less reliable
> than the SLC NAND being used with yaffs2. Any improved reliability would
> come from the algorithms these chips are using internally to manage the
> flash, and since we can't see those algorithms it's pretty difficult to
> say which will be more reliable. Filesystems designed for HDDs may have
> access patterns that accelerate wear on the flash as compared to
> designed-for-flash filesystems as well.
>
> The numbers I've seen do show yaffs2 on SLC performing better than
> the ext family of filesystems on eMMC however.

Is there any performance measurement tool for FS to compare against
SLC(NAND) and eMMC??
Would be dleighted to see any such tools

>
>> ext3 and ext4 become more practical and reasonable to use.  Yes yaffs2
>> seemed to be dominant in the last few years.  I think you will see a shift
>> away from this.
>
> I think that's true, but it probably has as much to do with cost as
> anything.
>

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>

Thanks and regards,
Ram.

[Seth Forshee]

On Tue, Sep 28, 2010 at 09:32:57AM -0700, Janakiram Sistla wrote:
> On Tue, Sep 28, 2010 at 9:22 AM, Seth Forshee <seth.f...@gmail.com> wrote:
> > On Mon, Sep 27, 2010 at 04:13:50PM -0700, The Dixter wrote:
> >> I think you will find more and more products use eMMC, which theoretically
> >> is more reliable, as the hardware handles bad blocks on its own.  Therefore,
> >
> > eMMC is based on MLC NAND, which at the hardware level is less reliable
> > than the SLC NAND being used with yaffs2. Any improved reliability would
> > come from the algorithms these chips are using internally to manage the
> > flash, and since we can't see those algorithms it's pretty difficult to
> > say which will be more reliable. Filesystems designed for HDDs may have
> > access patterns that accelerate wear on the flash as compared to
> > designed-for-flash filesystems as well.
> >
> > The numbers I've seen do show yaffs2 on SLC performing better than
> > the ext family of filesystems on eMMC however.
>
> Is there any performance measurement tool for FS to compare against
> SLC(NAND) and eMMC??
> Would be dleighted to see any such tools

I'd think that most filesystem benchmark tools ought to work, but I
haven't done this analysis personally so I can't say for certain about
any specific tool. I have used bonnie++ in the past. Of course getting
those sorts of tools to build for Android can often be a challenge,
missing dependencies and such, but if you have a more standard Linux
environment running against the same kernel version the results should
be similar.