From: Linus Torvalds <torvalds@linux-foundation.org>
To: David Dillow <dave@thedillows.org>
Cc: Linus Torvalds <torvalds@linuxfoundation.org>,
"Frank Ch. Eigler" <fche@redhat.com>,
Junio C Hamano <gitster@pobox.com>,
Git Mailing List <git@vger.kernel.org>
Subject: Re: reducing prune sync()s
Date: Thu, 29 May 2008 19:30:59 -0700 (PDT) [thread overview]
Message-ID: <alpine.LFD.1.10.0805291923030.3141@woody.linux-foundation.org> (raw)
In-Reply-To: <alpine.LFD.1.10.0805291905360.3141@woody.linux-foundation.org>
On Thu, 29 May 2008, Linus Torvalds wrote:
>
> So if you have a system crash at a really bad time, you may have a git
> repository that needs manual intervention to actually be *usable*. I hope
> nobody ever believed anything else. That manual intervention may be things
> like:
> ...
> - actually throw away broken commits, and re-create them (ie basically
> doing a "git reset <known-good-state>" plus re-committing the working
> tree or perhaps re-doing a whole "git am" series or something)
The important part here is that it's only the *new* state that can be this
kind of "broken commits". In other words, you'd never have to re-do actual
*old* commits, just the commits you were doing as things crashed - the
commits that you were in the middle of doing, and still have the data for.
Example from my case: I may have series of 250+ commits that I create with
"git am" when I sync up with Andrew, and I very much want the speed of
being able to create all that new commit data without ever even causing a
_single_ synchronous disk write.
So if the machine were to crash in the middle of the series, I might lose
all of that data, but I still have my mailbox, so I'd just need to reset
to the point before I even started the "git am", and re-do the whole
series. My actual *base* repository objects would never get corrupted.
[ And one final notice: I don't know about others, but I've actually had
more corruption from disks going bad etc that from system crashes per
se. And when *that* happens, old data is obviously as easily gone as new
data is. So absolutely _nothing_ replaces backups. It doesn't matter if
you do a "fsync()" after every single byte write - a disk crash can and
will corrupt things that were "stable". So even "stable storage" is
very much unstable in the end. ]
Linus
next prev parent reply other threads:[~2008-05-30 2:33 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-29 20:57 reducing prune sync()s Frank Ch. Eigler
2008-05-30 0:27 ` Linus Torvalds
2008-05-30 0:32 ` Linus Torvalds
2008-05-30 1:50 ` Frank Ch. Eigler
2008-05-30 20:07 ` Florian Weimer
2008-05-30 1:51 ` David Dillow
2008-05-30 2:17 ` Linus Torvalds
2008-05-30 2:30 ` Linus Torvalds [this message]
2008-05-30 15:25 ` Frank Ch. Eigler
2008-05-30 15:57 ` Linus Torvalds
2008-05-30 16:08 ` [PATCH 1/2] Make pack creation always fsync() the result Linus Torvalds
2008-05-30 16:11 ` [PATCH 2/2] Remove now unnecessary 'sync()' calls Linus Torvalds
2008-05-30 20:27 ` [PATCH 1/2] Make pack creation always fsync() the result Nicolas Pitre
2008-05-31 14:19 ` Frank Ch. Eigler
2008-06-02 22:23 ` Linus Torvalds
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=alpine.LFD.1.10.0805291923030.3141@woody.linux-foundation.org \
--to=torvalds@linux-foundation.org \
--cc=dave@thedillows.org \
--cc=fche@redhat.com \
--cc=git@vger.kernel.org \
--cc=gitster@pobox.com \
--cc=torvalds@linuxfoundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).