On Tue, Feb 01, 2011 at 07:52:59AM +1100, NeilBrown wrote: > On Mon, 31 Jan 2011 21:20:55 +0100 Piergiorgio Sartor > <piergiorgio.sartor@xxxxxxxx> wrote: > > > Hi all, > > > > some times ago, I think was Neil, it was mentioned > > about the possibility to access consistently a RAID-6 > > array from user space, in order to be able to perform > > some checks, like the notorius "which HDD has wrong data". > > > > Is there any reference or documentation or source code > > which can be taken as example for such a case? > > > > Look in the mdadm source code, particularly at restripe.c > > Also > make test_stripe > > make a program the the test suite uses for verify data correctness. > > That should give you enough hints to get you started. Hi Neil, thanks for the pointer. I had a look at the code and there is something I did not get. It seems to me the HDDs composing the array are "simply" opened with "open". In case the array is in use, how is avoided a race condition between the "test_stripe" program and the md device? I mean, the first could start to read from the HDDs and the other could write something in the same place, leading to an inconsistent parity, from the "test_stripe" point of view, since it missed some update. Or there is a locking inside md (in "test_stripe" I could not see and it would also be dangerous)? Thanks again, bye, -- piergiorgio -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
