From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Dong Subject: Re: Unexpected reset corrupted Reiser4 filesystem Date: Wed, 25 May 2005 06:46:10 -0400 Message-ID: References: <200505242338.32420.ajwade@cpe00095b3131a0-cm0011ae8cd564.cpe.net.cable.rogers.com> <429403EF.4030803@slaphack.com> Reply-To: John Dong Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_17753_5724551.1117017970133" Return-path: list-help: list-unsubscribe: list-post: Errors-To: flx@namesys.com In-Reply-To: <429403EF.4030803@slaphack.com> List-Id: To: reiserfs-list@namesys.com ------=_Part_17753_5724551.1117017970133 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline If thse were IDE drives, the IDE writeback cache is probably the bad boy --= =20 on FreeBSD 5.x, Soft Updates is virtually broken on IDE drives because they= =20 simply haven't written all the data they promised the kernel that they had. On 5/25/05, David Masover wrote: >=20 > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 >=20 > Andrew James Wade wrote: > > Hello, > > > > One of my Reiser4 filesystems was corrupted by a power glitch. >=20 > No filesystem can prepare for a power glitch, AFAIK. >=20 > > fsck fixed the corruption, but my understanding is that an > > unexpected reset should not have corrupted the filesystem. I >=20 > It's my understanding that an unexpected _should_ not have corrupted the > filesystem. Generally, this means that if we have everything working > the way it's supposed to right up until someone hits the Reset switch, > there _should_ be zero corruption. >=20 > Caveats: > 1.) _should_ is not _is_. Just because the developers can't crash it > doesn't mean it's invulnerable. > 2.) power flicker is different than the power/reset button. It really > all depends on what your hardware actually does when power is cut, but > most hard drives do some sort of write caching, and some of them make it > impossible to turn that off. >=20 > To say more, I'd have to know about the physical mechanics involved, but > even if you could make the system absolutely invulnerable to power loss, > you're still going to lose data (not corrupt -- LOSE) in such an event, > unless you have a battery backup. Even then, your drive is eventually > going to fail -- so use RAID. And someone is eventually going to rm -rf > your RAID, or spill coffee on it, or hit it with a > tornado/earthquake/nuke, so have multiple sites and make backups. >=20 > That's what it all comes down to -- make backups. The fact that you > have journalling/transactions/fsck/batteries/RAID is all just to make it > a little less catostrophic when stuff does fail. >=20 > > have an image of the corrupted filesystem, is it of any use to > > anyone? >=20 > Probably someone, not me. I don't work here, but I'll bet money that > they are going to ask for something from debugfs. >=20 > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.1 (GNU/Linux) > Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org >=20 > iQIVAwUBQpQD7ngHNmZLgCUhAQLvSA//bPqBcYMs/NRS7mT//zlGF0WK2YlnNUCd > 2hvzXxQhKcLMIvaTo9DJ9wzkaDIHot1DZUcuFIU3f4qmb7QIlMbkVoYE1AW34Wg/ > /G06KTkHUi0iU+GJ9Dq65Oj4nK1SM4AtBHMpLqhpcW0FExsj9ScmewcSehFNSzDS > Frptzvk/iWtkip2rJxReF8rKr170Y2aR+1DNaCUiLLoESTgbF5WMmcJFyyuaa0/y > JbP8/kTz4mbLuZuIt6qKswHqUACUA98sK32zeylUOeccKih35FkiaZtegIwti6Op > QwfuCQNyhlODVxAUCghMxz6RtF59Zk4hfoWv5f1GHB7/MHgHGQmMeBy3G/Y/y8D/ > P29LVyjhyStVmRyfYtDewMIBQz+nx1+StTqZ3jimfwlpMZxOxeGc0IbV9qiM4o6U > uYgtf9nrdeywn2HruijYO5xiTUcIbaBUGsvCCxNYrdzMYKEDsk3iTR/Jrxl/8GJl > d88NwSAdiU+uUcPkfdlcl+bHk3SB1yX7sjbItOtrUgZxFYsjtuFOusaOo5CkT84l > 2lduqioG2u4zWirRk3d3QJEWETykhX4JnjnCjw/qAQ9+JOLc5xjUbgO2fB8d1toy > QKGGVTH1P3i8Ux5ISrtP3noNtA/zzGRlhYShzc50bq8c8+/CAiqnx9FZGv854Ttp > hpTuQ1Ht0FA=3D > =3D1k9p > -----END PGP SIGNATURE----- > ------=_Part_17753_5724551.1117017970133 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline If thse were IDE drives, the IDE writeback cache is probably the bad boy -- on FreeBSD 5.x, Soft Updates is virtually broken on IDE drives because they simply haven't written all the data they promised the kernel that they had.

On 5/25/05, <= b class=3D"gmail_sendername">David Masover <ninja@slaphack.com> wrote:
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Andrew James Wade w= rote:
> Hello,
>
> One of my Reiser4 filesystems was corr= upted by a power glitch.

No filesystem can prepare for a power glitc= h, AFAIK.

> fsck fixed the corruption, but my understanding is that an
= > unexpected reset should not have corrupted the filesystem. I

It= 's my understanding that an unexpected _should_ not have corrupted the
filesystem.  Generally, this means that if we have everything wor= king
the way it's supposed to right up until someone hits the Reset swit= ch,
there _should_ be zero corruption.

Caveats:
1.)  = ;_should_ is not _is_.  Just because the developers can't crash i= t
doesn't mean it's invulnerable.
2.)  power flicker is diff= erent than the power/reset button.  It really
all depends on w= hat your hardware actually does when power is cut, but
most hard drives = do some sort of write caching, and some of them make it
impossible to turn that off.

To say more, I'd have to know about= the physical mechanics involved, but
even if you could make the system = absolutely invulnerable to power loss,
you're still going to lose data (= not corrupt -- LOSE) in such an event,
unless you have a battery backup.  Even then, your drive is e= ventually
going to fail -- so use RAID.  And someone is eventu= ally going to rm -rf
your RAID, or spill coffee on it, or hit it with a<= br>tornado/earthquake/nuke, so have multiple sites and make backups.

That's what it all comes down to -- make backups.  The fa= ct that you
have journalling/transactions/fsck/batteries/RAID is all jus= t to make it
a little less catostrophic when stuff does fail.

>= ; have an image of the corrupted filesystem, is it of any use to
> anyone?

Probably someone, not me.  I don't work h= ere, but I'll bet money that
they are going to ask for something from de= bugfs.

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