From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f41.google.com ([74.125.82.41]:38907 "EHLO mail-wm0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750873AbcI3Xqx (ORCPT ); Fri, 30 Sep 2016 19:46:53 -0400 Received: by mail-wm0-f41.google.com with SMTP id p138so51234418wmb.1 for ; Fri, 30 Sep 2016 16:46:52 -0700 (PDT) Subject: Re: multi-device btrfs with single data mode and disk failure To: Chris Murphy References: <1634818f-ff1d-722c-6d73-747ed7203a13@gmail.com> <760be1b7-79b2-a25d-7c60-04ceac1b6e40@gmail.com> <3460a1ac-7e66-cf6f-b229-06a0825401a5@gmail.com> <64102181-e02d-69a8-ead7-a27acadbe6a8@gmail.com> <4e7ec5eb-7fb6-2d19-f29d-82461e2d0bd2@gmail.com> <0b29471c-363a-1e2f-d352-1d422c07df64@gmail.com> Cc: Btrfs BTRFS From: Alexandre Poux Message-ID: <0a5e6528-f929-729b-a608-a46dc6f8a6a3@gmail.com> Date: Sat, 1 Oct 2016 01:46:49 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: Hello again, Just a quick question. I did a full scrub and got no error at all And a full check that gave me this : #> btrfs check --check-data-csum -p /dev/sde6 Checking filesystem on /dev/sde6 UUID: 62db560b-a040-4c64-b613-6e7db033dc4d checking extents [o] checking free space cache [o] checking fs roots [.] checking csums checking root refs checking quota groups Counts for qgroup id: 0/5 are different our: referenced 7239132803072 referenced compressed 7239132803072 disk: referenced 7238982733824 referenced compressed 7238982733824 diff: referenced 150069248 referenced compressed 150069248 our: exclusive 7239132803072 exclusive compressed 7239132803072 disk: exclusive 7238982733824 exclusive compressed 7238982733824 diff: exclusive 150069248 exclusive compressed 150069248 found 7323422314496 bytes used err is 0 total csum bytes: 7020314688 total tree bytes: 11797741568 total fs tree bytes: 2904932352 total extent tree bytes: 656654336 btree space waste bytes: 1560529439 file data blocks allocated: 297363385454592 referenced 6628544720896 I'm guessing that's not important, but I found nothing about this so I don't really know what's about. Can just confirm that everything seems OK ? Do you think of an another test I should do before starting to use my array again ? Le 29/09/2016 à 14:55, Alexandre Poux a écrit : > Hi, > > I finally did it : patched the kernel and removed the device. > As expected he did not scream since there was nothing at all on the device. > Now I'm checking that everything is fine: > scrub (in read only) > check (in read only) > but I think that everything will be OK > If not, I will rebuild the array from scratch (I did managed to save my > data) > > Thank you both for your guidance. > I think that a warning should be put in the wiki in order for other user > to not do the same mistake I did : > never ever use the single mode > > I will try to do it soon > > Again thank you > > Le 20/09/2016 à 23:15, Chris Murphy a écrit : >> On Tue, Sep 20, 2016 at 2:18 PM, Alexandre Poux wrote: >>> Le 20/09/2016 à 21:46, Chris Murphy a écrit : >>>> On Tue, Sep 20, 2016 at 1:31 PM, Alexandre Poux wrote: >>>>> Le 20/09/2016 à 21:11, Chris Murphy a écrit : >>>>>> And no backup? Umm, I'd resolve that sooner than anything else. >>>>> Yeah you are absolutely right, this was a temporary solution which came >>>>> to be not that temporary. >>>>> And I regret it already... >>>> Well on the bright side, if this were LVM or mdadm linear/concat >>>> array, the whole thing would be toast because any other file system >>>> would have lost too much fs metadata on the missing device. >>>> >>>>>> It >>>>>> should be true that it'll tolerate a read only mount indefinitely, but >>>>>> read write? Not sure. This sort of edge case isn't well tested at all >>>>>> seeing as it required changing the kernel to reduce safe guards. So >>>>>> all bets are off the whole thing could become unmountable, not even >>>>>> read only, and then it's a scraping job. >>>>> I'm not that crazy, I tried the patch inside a virtual machine on >>>>> virtual drives... >>>>> And since it's only virtual, it may not work on the real partition... >>>> Are you sure the virtual setup lacked a CHUNK_ITEM on the missing >>>> device? That might be what pinned it in that case. >>> In fact in my virtual setup there was more chunk missing (1 metadata 1 >>> System and 1 Data). >>> I will try to do a setup closer to my real one. >> Probably the reason why that missing device has no used chunks is >> because it's so small. Btrfs allocates block groups to devices with >> the most unallocated space first. Only once the unallocated space is >> even (approximately) on all devices would it allocate a block group to >> the small device. >> >> >