Re: ext4 features

Ric Wheeler
2006-07-06T15:19:56Z

Tomasz Torcz wrote:

>On Sat, Jul 01, 2006 at 07:47:16PM +0200, Thomas Glanzmann wrote:
>
>
>>Hello,
>>
>>
>>>Checksums are not very useful for themselves. They are useful when we
>>>have other copy of data (think raid mirroring) so data can be
>>>reconstructed from working copy.
>>>
>>>
>>it would be possible to identify data corruption.
>>
>>
>
> Yes, but what good is identification? We could only return I/O error.
>Ability to fix corruption (like ZFS) is the real killer.
>
>

Having a checksum (or even a digital signature on a file) that lets us
detect corruption is very useful since, in many cases, it allows us to
flag the file as corrupt before it gets used.

In some cases, this is a big hint that you should restore it from backup
(tape, other disk, etc).

I think that it is a generally useful thing even when not on a self
correcting device,

ric