Dne 6.11.2015 v 20:06 Sami Tolvanen napsal(a):
On Fri, Nov 06, 2015 at 12:23:29PM -0500, Mikulas Patocka wrote:
I'm also wondering what is this patch useful for. Disks and flash
controllers have their own error detection and correction
I think I addressed this earlier. Some storage devices are able to
correct bit flips, but don't have enough redundancy to correct larger
errors. Using this patch set we can correct N MiB of consecutive
corruption anywhere on the partition with the same amount of storage
overhead.
Another point - if the read-only system partition is experiencing some
errors, than the read-write partition will probably have errors too
On mobile devices, errors in read-only partitions often lead to
bricked devices while errors in the read-write parts might only lead
to lost cat photos. There are situations where people would prefer to
have a working phone even if it fails to store some of their data.
Do you have some real case where such error corrections
increase longevity of some device?
Yes, there have been several cases where read-only partition errors
have rendered a device unusable. The sheer volume of mobile devices
means that even if a tiny fraction of them suffer from such a problem,
it's going to affect a large number of people.
But you can take raid5 in read-only mode, put it on several partitions
protected with dm-verity and you get decent error correction
I agree. Unfortunately, we don't currently have the luxury of using
raid on mobile devices.
AFAIK - you just build as much partition as need to have some 'space'
dedicated for redundancy - and rest of 'partitions' you join as 'writable'
i.e. you have 1G of space - you want to give 250MB as 'redundancy' -
so create 4 partition....
Since phones starts to have 64GB of storage space - it looks like a way to go.....
As no one bothers to upgrade 'old' phone - why to focus there??
And BTW - already seen couple bricked Nexus7....
(And no marhmallow in plan....)
(And interestingly all killed I've seen were on Lolipop - none with Kitkat)
Zdenek
--
dm-devel mailing list
dm-devel@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/dm-devel
