On Wed, Sep 26, 2012 at 03:41:07PM +1000, NeilBrown wrote: > On Wed, 26 Sep 2012 06:57:29 +0200 Jakub Hus?k <jakub@xxxxxxxxxxx> wrote: > > > On 25.9.2012 14:32, NeilBrown wrote: > > > On Tue, 25 Sep 2012 11:48:34 +0200 <jakub@xxxxxxxxxxx> wrote: > > > > > >> > > >> Would you please refer to some documentation that this behaviour is > > >> correct? I now tried to fail several disks in raid5, raid0 and raid10-near, > > >> in case of r0 and r10n, mdadm didn't even allow me to remove more disks > > >> than is sufficient to access all the data. In case of r5 I was able to fail > > >> 2 out of 3, but the array was correctly marked as FAILED and couldn't be > > >> accessed at all. I'd expect that behaviour even in my case of raid10-far. I > > >> can't even assmenble and run it with less than required count of disks. > > >> > > > Could you please be explicit about exactly how the behaviour that you think > > > of as "correct" would differ from the current behaviour? Because I cannot > > > really see what point you are making - I need a little help. > > > > > > Thanks, > > > NeilBrown > > I think that when two adjacent drives fail, or the array is being > > assembled with two adjacent drives missing, the status wouldn't be > > "clean, degraded", the array "running" and reporting some inaccessible > > blocks when you try to use it - as it happens in my case of R10F. > > Instead, the array status would be "FAILED " and won't be allowed to > > run. R0, R5, R10N behave in that manner (if i tested well), which I > > consider correct. > > > > The "degraded" status means, at lest for me, that the array is fully > > functional, only with limited redundancy. > > R10 with far2 layout and four disks can't be only "degraded" when any > > two disks are missing, unlike R10 near2 in some cases. > > > > If something is still not clear, please be patient, i'll try to squeeze > > maximum out of my torturous English ;) > > > > Thaks > > Ahh.... I see it now. > There is a bug in the 'enough' function in mdadm and in drivers/md/raid10.c > It doesn't handle 'far' layouts properly. > > I'll sort out some patches. I also understand it now, I think. raid10,f2 with 4 disks cannot in the current implementation survive 2 failing disks. We have discussed earlier how to implement raid10,far that would mean better survival chances with more disks failing. This is not implemented yet. Best regards Keld -- 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
