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Re: ext3 Overhead


"Stephen C. Tweedie" <sct redhat com> wrote:

>On Thu, 2004-02-19 at 13:01, christian braun ch abb com wrote:
>> 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?
> For data, there's no difference --- unless you're in data=journal mode
> --- except for the fact that ext3 usually starts flushing stuff to disk
> earlier than ext2, which can mean that ext3 writes temporary data more
> often than ext2.  For metadata, I'd expect ext3 is at most twice the
> writes of ext2 in most circumstances, but it's not something I've ever
> measured.

Most probably even more. Imagine deleting a directory recursively. On ext2 
most unlink operations will cause only one write operation to disk. On ext3 
each unlink operation creates at least one extra journal entry (plus the 
write of the directory blocks). Same for modifications to the block bitmaps 
and so on.

Regards, Bodo

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