generally, anything u write for ext2, should still be valid for ext3, and ext4. in the sense that the features are backward compatible. sizing limits may have increased, but OLD working mechanism should still be valid....except for some.<div>
<br></div><div>so ext2 fs should still be mountable as ext4, but not vice versa, once some flag is enabled (I think it is xattr). and if the flag is not enabled, and the journal logs is clean, then ext4 fs is also mountable as ext2 fs:</div>
<div><br></div><div><a href="http://superuser.com/questions/408822/ext4-converted-mounted-as-ext2">http://superuser.com/questions/408822/ext4-converted-mounted-as-ext2</a></div><div><br></div><div><div><a href="http://computer-forensics.sans.org/blog/2011/06/14/digital-forensics-mounting-dirty-ext4-filesystems">http://computer-forensics.sans.org/blog/2011/06/14/digital-forensics-mounting-dirty-ext4-filesystems</a></div>
</div><div><br></div><div><a href="http://en.wikipedia.org/wiki/Extended_file_attributes">http://en.wikipedia.org/wiki/Extended_file_attributes</a></div><div><br></div><div><div class="gmail_quote">On Sun, Feb 3, 2013 at 12:26 AM, Rami Rosen <span dir="ltr"><<a href="mailto:roszenrami@gmail.com" target="_blank">roszenrami@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi,<br>
<div class="im">> ext2 and ext3 are kind of obsolete now.<br>
<br>
</div>Indeed, ext4 was integrated into Linux kernel back in 2008.<br>
Amongs its known features which do not exist in ext3 are support for<br>
huge files (like 1 EB (exabyte or somtimes termed exbibyte); 1 EB is<br>
1024 PB (petabyte) whereas<br>
1 PB is 1024 TB (terabyte).<br>
a directory can contain a maximum of 64,000 subdirectories (whereas we<br>
have 32,000 in ext3)<br>
Amongst its other features are Journal checksumming, Multiblock<br>
allocator, Faster file system checking and more.<br>
<br>
<br>
If you prefer to start with simpler implementations, ext3 is of course<br>
simpler, and of course ext2 is even simpler than ext3.<br>
<br>
But in case you intend to start with ext2/ext3, and later perform<br>
a pass on all your documentation to update it to ext4, take into<br>
consideration that this will take quite a time; depending on how deep<br>
you intend to delve into implementation details.<br>
<br>
Good luck!<br>
<div class="im HOEnZb"><br>
Regards,<br>
Rami Rosen<br>
<a href="http://ramirose.wix.com/ramirosen" target="_blank">http://ramirose.wix.com/ramirosen</a><br>
<br>
<br>
<br>
</div><div class="HOEnZb"><div class="h5">On Sat, Feb 2, 2013 at 11:43 AM, Shubham Sharma<br>
<<a href="mailto:kernel.shubham@gmail.com">kernel.shubham@gmail.com</a>> wrote:<br>
> Hi,<br>
><br>
> I understand that ext2 and ext3 are kind of obsolete now. But AFAIK, there<br>
> is not much difference in ext3 and ext4.<br>
><br>
> Moreover for a newbie , it is better to start with ext3. What you think ?<br>
><br>
> Regards<br>
> Shubham<br>
><br>
><br>
> On Fri, Feb 1, 2013 at 2:15 AM, Rami Rosen <<a href="mailto:roszenrami@gmail.com">roszenrami@gmail.com</a>> wrote:<br>
>><br>
>> Hi,<br>
>> Have you considered to start with ext4?<br>
>> it seems that ext3, ext2 are a bit out of fashion,<br>
>><br>
>> Regards,<br>
>> Rami Rosen<br>
>> <a href="http://ramirose.wix.com/ramirosen" target="_blank">http://ramirose.wix.com/ramirosen</a><br>
>><br>
>><br>
>> On Thu, Jan 31, 2013 at 8:58 PM, shubham <<a href="mailto:kernel.shubham@gmail.com">kernel.shubham@gmail.com</a>> wrote:<br>
>> > Thanks Rami,<br>
>> ><br>
>> > I am also trying to understand ext3 and write some document for the<br>
>> > same.<br>
>> ><br>
>> > Regards<br>
>> > Shubham<br>
>> ><br>
>> ><br>
>> > On 31-Jan-13 12:51 AM, Rami Rosen wrote:<br>
>> >><br>
>> >> HI,<br>
>> >> I will try to write something for Linux Filesystems (and maybe for<br>
>> >> other subsystems) but this will probably take a lot of time.<br>
>> >><br>
>> >> Regards,<br>
>> >> Rami Rosen<br>
>> >> <a href="http://ramirose.wix.com/ramirosen" target="_blank">http://ramirose.wix.com/ramirosen</a><br>
>> >><br>
>> >><br>
>> >> On Wed, Jan 30, 2013 at 5:44 PM, shubham <<a href="mailto:kernel.shubham@gmail.com">kernel.shubham@gmail.com</a>><br>
>> >> wrote:<br>
>> >>><br>
>> >>> Thanks for sharing the document.<br>
>> >>><br>
>> >>> I hope we could have such documents for other subsystems as well.<br>
>> >>><br>
>> >>> Regards<br>
>> >>> Shubham<br>
>> >>><br>
>> >>><br>
>> >>> On 28-Jan-13 10:23 PM, Rami Rosen wrote:<br>
>> >>>><br>
>> >>>> Hi everyone,<br>
>> >>>> You can find here an up to date and detailed document in pdf (178<br>
>> >>>> pages) about Linux Kernel Networking; going deep into design and<br>
>> >>>> implementation details as well as the theory behind it:<br>
>> >>>> <a href="http://media.wix.com/ugd//295986_931b8bcf34d93419d46e05b5aa5d0216.pdf" target="_blank">http://media.wix.com/ugd//295986_931b8bcf34d93419d46e05b5aa5d0216.pdf</a><br>
>> >>>><br>
>> >>>> I believe that developers/sysadmins/researchers/students may find<br>
>> >>>> help<br>
>> >>>> with it.<br>
>> >>>><br>
>> >>>><br>
>> >>>> regards,<br>
>> >>>> Rami Rosen<br>
>> >>>><br>
>> >>>> <a href="http://ramirose.wix.com/ramirosen" target="_blank">http://ramirose.wix.com/ramirosen</a><br>
>> >>>><br>
>> >>>> _______________________________________________<br>
>> >>>> Kernelnewbies mailing list<br>
>> >>>> <a href="mailto:Kernelnewbies@kernelnewbies.org">Kernelnewbies@kernelnewbies.org</a><br>
>> >>>> <a href="http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies" target="_blank">http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies</a><br>
>> >>><br>
>> >>><br>
>> ><br>
><br>
><br>
<br>
_______________________________________________<br>
Kernelnewbies mailing list<br>
<a href="mailto:Kernelnewbies@kernelnewbies.org">Kernelnewbies@kernelnewbies.org</a><br>
<a href="http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies" target="_blank">http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies</a><br>
</div></div></blockquote></div><br><br clear="all"><div><br></div>-- <br>Regards,<br>Peter Teoh
</div>