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Date:      Sun, 20 Mar 2011 23:45:04 -0600
From:      Scott Long <scottl@samsco.org>
To:        Jeff Roberson <jroberson@jroberson.net>
Cc:        Doug Barton <dougb@FreeBSD.org>, kvedulv@kvedulv.de, Jeff Roberson <jeff@FreeBSD.org>, Kirk McKusick <mckusick@mckusick.com>, Gavin Atkinson <gavin@FreeBSD.org>, Nathan Whitehorn <nwhitehorn@FreeBSD.org>, src-committers@FreeBSD.org, Marius Strobl <marius@alchemy.franken.de>, svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org
Subject:   Re: svn commit: r219667 - head/usr.sbin/bsdinstall/partedit 
Message-ID:  <25AA5841-B700-463A-BD52-9FD18650E859@samsco.org>
In-Reply-To: <alpine.BSF.2.00.1103201831270.1480@desktop>
References:  <201103210342.p2L3gWM9057768@chez.mckusick.com> <alpine.BSF.2.00.1103201831270.1480@desktop>

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On Mar 20, 2011, at 10:34 PM, Jeff Roberson wrote:

> On Sun, 20 Mar 2011, Kirk McKusick wrote:
>=20
>>> Date: Sun, 20 Mar 2011 13:25:20 -0700
>>> From: Doug Barton <dougb@FreeBSD.org>
>>> To: Marius Strobl <marius@alchemy.franken.de>
>>> CC: Kirk McKusick <mckusick@mckusick.com>,
>>>       Nathan Whitehorn <nwhitehorn@FreeBSD.org>, =
svn-src-head@FreeBSD.org,
>>>       Jeff Roberson <jeff@FreeBSD.org>, Gavin Atkinson =
<gavin@FreeBSD.org>,
>>>       svn-src-all@FreeBSD.org, src-committers@FreeBSD.org,
>>>       kvedulv@kvedulv.de
>>> Subject: Re: svn commit: r219667 - head/usr.sbin/bsdinstall/partedit
>>>=20
>>> On 03/20/2011 09:22, Marius Strobl wrote:
>>>=20
>>>> I fear it's still a bit premature for enable SU+J by default. =
Rather
>>>> recently I was told about a SU+J filesystems lost after a panic
>>>> that happend after snapshotting it (report CC'ed, maybe he can
>>>> provide some more details) and I'm pretty sure I've seen the =
problem
>>>> described in PR 149022 also after the potential fix mentioned in =
its
>>>> feedback.
>>>=20
>>> +1
>>>=20
>>> I tried enabling SU+J on my /var (after backing up of course) and =
after
>>> a panic random files were missing entirely. Not the last updates to
>>> those files, the whole file, and many of them had not been written =
to in
>>> days/weeks/months.
>>>=20
>>> With all due respect to the hard work that went into the code, I =
would
>>> be very uncomfortable with enabling it by default at this point.
>>>=20
>>>=20
>>> Doug
>>=20
>> With all due respect, how can we fix things that nobody reports?
>> If you have a problem, let us know about it. And of course, we
>> need something more specific than the above.
>=20
> I have not been following current but I read any emails sent directly =
to me without a mailing list in the cc.  I also was not aware of this.  =
I had not heard of any filesystem corruption problems at all.  If there =
are any, I also am not comfortable with enabling it by default.  I want =
to fix that first.
>=20
> I have blocked off next week to work on this.  I already sent an email =
out to current@ requesting bug reports.  Please if you have anything =
else let me know immediately so I can prioritize it and start =
investigating.
>=20

I haven't seen any data/metadata corruption issues with SUJ that weren't =
also present with SU (or just plain UFS).  The vast majority of problems =
that I've witnessed have happened on systems with ATA/SATA disks, =
hinting (IMHO) that it's really the long-standing problem of running =
these disks with their write caches enabled.  I don't think that I've =
encountered any appreciable problems on RAID controllers or SAS/SCSI =
disks with their write caches disabled.  Maybe with CAMATA maturing and =
supporting NCQ, we can turn off the SATA write caches as the default =
policy.

Scott





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