Grzegorz Kulewski a écrit :
Hi,
On Thu, 2 Nov 2006, Mikulas Patocka wrote:
As my PhD thesis, I am designing and writing a filesystem, and it's
now in a state that it can be released. You can download it from
http://artax.karlin.mff.cuni.cz/~mikulas/spadfs/
"Disk that can atomically write one sector (512 bytes) so that the sector
contains either old or new content in case of crash."
Well, maybe I am completly wrong but as far as I understand no disk
currently will provide such requirement. Disks can have (after halted
write):
- old data,
- new data,
- nothing (unreadable sector - result of not full write and disk
internal checksum failute for that sector, happens especially often if
you have frequent power outages).
I believe some vendors have such devices. Mikulas called them 'disk', but it's
in fact a (disk(s), controler, ram, battery)
Some controlers are even able to write into flash memory the un-written data
when/if the battery/power is about to fail. When power goes up, controler can
finaly do the writes on disks.
And possibly some broken drives may also return you something that they
think is good data but really is not (shouldn't happen since both disks
and cables should be protected by checksums, but hey... you can never be
absolutely sure especially on very big storages).
So... isn't this making your filesystem a little flawed in design?
Well... even RAM can fail :) In this case isnt linux flawed in design ?
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