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From: Chris Murphy <lists@colorremedies.com>
To: Chris Murphy <lists@colorremedies.com>
Cc: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>,
	Phil Karn <karn@ka9q.net>, Paul Jones <paul@pauljones.id.au>,
	"linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>
Subject: Re: Extremely slow device removals
Date: Sun, 3 May 2020 00:05:10 -0600	[thread overview]
Message-ID: <CAJCQCtQaTH1S-MRMOWAJXgq-NRNq1U5kaksj6Xr3z_MCj2YVGw@mail.gmail.com> (raw)
In-Reply-To: <CAJCQCtSr-1dM7DwUh0TQ0d-B9gAfrMVzHEZ=ZTzv7utf30WGcw@mail.gmail.com>

On Sat, May 2, 2020 at 11:39 PM Chris Murphy <lists@colorremedies.com> wrote:
>
> On Sat, May 2, 2020 at 11:26 PM Zygo Blaxell
> <ce3g8jdj@umail.furryterror.org> wrote:
> >
> > On Sat, May 02, 2020 at 11:48:18AM -0600, Chris Murphy wrote:
> > > On Sat, May 2, 2020 at 3:09 AM Zygo Blaxell
> > > <ce3g8jdj@umail.furryterror.org> wrote:
> > > >
> > > > On SD/MMC and below-$50 SSDs, silent data corruption is the most common
> > > > failure mode.  I don't think these disks are capable of detecting or
> > > > reporting individual sector errors.  I've never seen it happen.  They
> > > > either fall off the bus or they have a catastrophic failure and give
> > > > an error on every single access.
> > >
> > > I'm still curious about the allocator to use for this device class. SD
> > > Cards usually self-report rotational=0. Whereas USB sticks report
> > > rotational=1. The man page seems to suggest nossd or ssd_spread.
> >
> > Use dup metadata on all single-disk filesystems, unless you are making
> > an intentionally temporary filesystem (like a RAM disk, or a cache with
> > totally expendable contents).  The correct function for maximizing btrfs
> > lifetime does not have "rotational" as a parameter.
>
> Btrfs defaults need to do the right thing. Currently it's single
> metadata for mkfs, and ssd mount option when sysfs reports the device
> rotational is false. This applies to eMMC and SD Cards. Whereas USB
> sticks report they're rotational for whatever reason, and in that case
> the default is DUP and nossd. But I don't know that rotational is the
> best way of assuming an allocator.

You address this in another thread: It's a bit unfortunate that
btrfs's default is still to use single metadata on SSD.


All I care about is detection on cheap SSDs. At least in my use cases,
I'm not sure it's worth the extra writes from DUP to be able to
recover from silent corruption.


-- 
Chris Murphy

  reply	other threads:[~2020-05-03  6:05 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-28  7:22 Extremely slow device removals Phil Karn
2020-04-30 17:31 ` Phil Karn
2020-04-30 18:13   ` Jean-Denis Girard
2020-05-01  8:05     ` Phil Karn
2020-05-02  3:35       ` Zygo Blaxell
     [not found]         ` <CAMwB8mjUw+KV8mxg8ynPsv0sj5vSpwG7_khw=oP5n+SnPYzumQ@mail.gmail.com>
2020-05-02  4:31           ` Zygo Blaxell
2020-05-02  4:48         ` Paul Jones
2020-05-02  5:25           ` Phil Karn
2020-05-02  6:04             ` Remi Gauvin
2020-05-02  7:20             ` Zygo Blaxell
2020-05-02  7:27               ` Phil Karn
2020-05-02  7:52                 ` Zygo Blaxell
2020-05-02  6:00           ` Zygo Blaxell
2020-05-02  6:23             ` Paul Jones
2020-05-02  7:20               ` Phil Karn
2020-05-02  7:42                 ` Zygo Blaxell
2020-05-02  8:22                   ` Phil Karn
2020-05-02  8:24                     ` Phil Karn
2020-05-02  9:09                     ` Zygo Blaxell
2020-05-02 17:48                       ` Chris Murphy
2020-05-03  5:26                         ` Zygo Blaxell
2020-05-03  5:39                           ` Chris Murphy
2020-05-03  6:05                             ` Chris Murphy [this message]
2020-05-04  2:09                         ` Phil Karn
2020-05-02  7:43                 ` Jukka Larja
2020-05-02  4:49         ` Phil Karn
2020-04-30 18:40   ` Chris Murphy
2020-04-30 19:59     ` Phil Karn
2020-04-30 20:27       ` Alexandru Dordea
2020-04-30 20:58         ` Phil Karn
2020-05-01  2:47       ` Zygo Blaxell
2020-05-01  4:48         ` Phil Karn
2020-05-01  6:05           ` Alexandru Dordea
2020-05-01  7:29             ` Phil Karn
2020-05-02  4:18               ` Zygo Blaxell
2020-05-02  4:48                 ` Phil Karn
2020-05-02  5:00                 ` Phil Karn
2020-05-03  2:28                 ` Phil Karn
2020-05-04  7:39                   ` Phil Karn

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