Dne 12.11.2014 v 12:00 Josef Bacik napsal(a):
On 11/12/2014 03:45 AM, Zdenek Kabelac wrote:
Dne 12.11.2014 v 03:30 Josef Bacik napsal(a):
Sorry for top posting, my phone client doesn't do inline.
I'm splitting the disk in half, writing to alternating sides of the
disk and keeping track of where which block is so when the power fail
event occurs the subsequent reads come from the corresponding mirror
in the disk. The disk needs to appear to be size/2 for the mkfs to
know the correct size, but my target needs to be able to write up to
size. I looked at thinp but it reflects the full size right? It's
just like a sparse find correct? My ->map function does the right
thing, doing the ->len trick makes it all work out right, but this is
really isolated testing. Thanks,
Just a side note - maybe you would like to rather extend functionality
of dm-flakey target ?
I did that first but it ended up being really ugly. With all the varying
functionality in dm-flakey it ended up making the table format horrible and
the code a spaghetti of if (test_bit()) crap everywhere. Thanks,
The other thing that lvm2 test suite is using is -
we take a base 'linear' device mapped on some origin - and we create a
segmented device where individual segment are either mapper to 'original'
device or to a 'zero' origin or 'error' origin depending on
whether you want to read 0 or 'err' from a device.
Example of such mapping 'trick':
normal mapping for device pv1:
pv1: 0 69120 linear 7:2 0
mapping with single error segment sector of device pv1:
pv1: 0 2050 linear 7:2 0
pv1: 2050 1 error
pv1: 2051 67069 linear 7:2 2051
You could reload table mapping for pv1 any-time with suspend/resume.
Zdenek
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