ext3 Overhead

[christian.braun at ch.abb.com]

Hello!



Message from "Stephen C. Tweedie" <sct at redhat.com> received on 13.02.2004 
12:12

13.02.2004 12:12



"Stephen C. Tweedie" <sct at redhat.com>





        To:     christian.braun at ch.abb.com
        cc:     ext3 users list <ext3-users at redhat.com>
        Subject:        Re: ext3 Overhead

Hi,

On Wed, 2004-02-11 at 14:55, christian.braun at ch.abb.com wrote:

> I'm using a CompactFlash as storage device. Since those CF cards only
> have limited write cycles (CF does wear-levelling by itself, but you
> don't want to write too many timet so the card) i was wondering by
> what a factor the journaling of ext3 increases the write accesses to
> the CompactFlash compared to ext2. Thanks a lot already for your help!

It increases the number of writes a bit, but in many cases might
actually reduce the number of overwrites for certain blocks like the
superblock, which can be an advantage for those CF cards that don't do
wear-levelling.  But it's really not a filesystem designed for flash.

--Stephen




On Wed, 2004-02-11 at 14:55, christian.braun at ch.abb.com wrote:

>> I'm using a CompactFlash as storage device. Since those CF cards only
>> have limited write cycles (CF does wear-levelling by itself, but you
>> don't want to write too many timet so the card) i was wondering by
>> what a factor the journaling of ext3 increases the write accesses to
>> the CompactFlash compared to ext2. Thanks a lot already for your help!
>
>It increases the number of writes a bit, but in many cases might
>actually reduce the number of overwrites for certain blocks like the
>superblock, which can be an advantage for those CF cards that don't do
>wear-levelling.  But it's really not a filesystem designed for flash.

Well, as I said my CF card does wear-levelling, so that's not to worry 
about. Still, as you said, there is a difference in the number of write 
accesses between ext2 and ext3... I just need to know in what region that 
difference is... is it 3 times... or 30 times... or 300... or even more?

Thank you!
Christian Braun