From: Johannes Hirte <johannes.hirte@datenkhaos.de>
To: Chris Murphy <lists@colorremedies.com>
Cc: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>,
Justin Engwer <justin@mautobu.com>,
Btrfs BTRFS <linux-btrfs@vger.kernel.org>
Subject: Re: I think he's dead, Jim
Date: Thu, 21 May 2020 00:15:08 +0200 [thread overview]
Message-ID: <20200520221508.GA28789@latitude> (raw)
In-Reply-To: <CAJCQCtSU9EyFDodLvpYMF+AU=i=-EFZNJw7h4vWL98vEz1jkvQ@mail.gmail.com>
On 2020 Mai 20, Chris Murphy wrote:
> On Wed, May 20, 2020 at 3:02 PM Johannes Hirte
> <johannes.hirte@datenkhaos.de> wrote:
> >
> > On 2020 Mai 19, Zygo Blaxell wrote:
> > >
> > > Corollary: Never use space_cache=v1 with raid5 or raid6 data.
> > > space_cache=v1 puts some metadata (free space cache) in data block
> > > groups, so it violates the "never use raid5 or raid6 for metadata" rule.
> > > space_cache=v2 eliminates this problem by storing the free space tree
> > > in metadata block groups.
> > >
> >
> > This should not be a real problem, as the space-cache can be discarded
> > and rebuild anytime. Or do I miss something?
>
> The bitmap locations for the free space cache are referred to in the
> extent tree. It's not as trivial update or drop the v1 space cache as
> it is the v2 which is in its own btree.
I still don't see the problem. Free space cache is needed for
performance, not function. If it's not available, this can be
ignored.
--
Regards,
Johannes Hirte
next prev parent reply other threads:[~2020-05-20 22:15 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-18 20:51 I think he's dead, Jim Justin Engwer
2020-05-18 23:23 ` Chris Murphy
[not found] ` <CAGAeKuv3y=rHvRsq6SVSQ+NadyUaFES94PpFu1zD74cO3B_eLA@mail.gmail.com>
[not found] ` <CAJCQCtQXR+x4mG+jT34nhkE69sP94yio-97MLmd_ugKS+m96DQ@mail.gmail.com>
2020-05-19 18:45 ` Justin Engwer
2020-05-19 20:44 ` Chris Murphy
2020-05-20 1:32 ` Zygo Blaxell
2020-05-20 20:53 ` Johannes Hirte
2020-05-20 21:35 ` Chris Murphy
2020-05-20 22:15 ` Johannes Hirte [this message]
2020-05-21 6:20 ` Zygo Blaxell
2020-05-21 17:24 ` Justin Engwer
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