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From: Chris Murphy <lists@colorremedies.com>
Date: Fri, 29 Jun 2018 18:04:51 -0600
Message-ID: <CAJCQCtQ1YuEpG0CXUVir5ZbADHxyB-NPDd7u8sFEtzJPmMOeMg@mail.gmail.com>
Subject: Re: So, does btrfs check lowmem take days? weeks?
To: Marc MERLIN <marc@merlins.org>
Cc: Qu Wenruo <quwenruo.btrfs@gmx.com>, Su Yue <suy.fnst@cn.fujitsu.com>,
        Btrfs BTRFS <linux-btrfs@vger.kernel.org>
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I've got about 1/2 the snapshots and less than 1/10th the data...but
my btrfs check times are much shorter than either: 15 minutes and 65
minutes (lowmem).


[chris@f28s ~]$ sudo btrfs fi us /mnt/first
Overall:
    Device size:        1024.00GiB
    Device allocated:         774.12GiB
    Device unallocated:         249.87GiB
    Device missing:             0.00B
    Used:             760.48GiB
    Free (estimated):         256.95GiB    (min: 132.01GiB)
    Data ratio:                  1.00
    Metadata ratio:              2.00
    Global reserve:         512.00MiB    (used: 0.00B)

Data,single: Size:761.00GiB, Used:753.93GiB
   /dev/mapper/first     761.00GiB

Metadata,DUP: Size:6.50GiB, Used:3.28GiB
   /dev/mapper/first      13.00GiB

System,DUP: Size:64.00MiB, Used:112.00KiB
   /dev/mapper/first     128.00MiB

Unallocated:
   /dev/mapper/first     249.87GiB


146 subvolumes
137 snapshots

total csum bytes: 790549924
total tree bytes: 3519250432
total fs tree bytes: 2546073600
total extent tree bytes: 131350528


Original mode check takes ~15 minutes
Lowmem mode takes ~65 minutes

RAM: 4G
CPU: Intel(R) Pentium(R) CPU  N3700  @ 1.60GHz



Chris Murphy