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  • From: Ryan Abrams <ryan.abrams AT attbi.com>
  • To: Casey Harkins <charkins AT upl.cs.wisc.edu>
  • Cc: Phil/CERisE/KG6MBQ <cerise AT littlegreenmen.armory.com>, <bluebird AT optushome.com.au>, <sm-discuss AT lists.ibiblio.org>
  • Subject: Re: [SM-Discuss] fresh install questions
  • Date: Thu, 25 Jul 2002 17:36:05 -0500

Right. But metadata should be enough. I guess what I am saying is that it
shouldn¹t consider the write action completed (and thus change the inode
journal entry) until all the data is written. Changing it before hand is
just stupid... Which is what xfs would have had to do. Otherwise the journal
would load and have a log of what the old inode was.. Thus no zeroed files.

But even if I don¹t know what the hell I am talking about (and its a
distinct possibility) - a file system that erases the old file pointer on
open, and THEN writes the new file.. Its um. Dumb.

-Ryan

On 7/25/02 3:41 PM, "Casey Harkins" <charkins AT upl.cs.wisc.edu> wrote:

> IIRC, ext3 is the only of the three that journals data portions of the
> filesystem. Reiser and XFS only journal the file metadata (name, size,
> inodes, perms).
>
> -casey
>
> On Thu, 25 Jul 2002, Ryan Abrams wrote:
>
>> That is an absolutely ridiculous way to handle files in a modern file
>> system. To the point that if it's true, I suggest no one use XFS.
>>
>> The whole point of journaling is that it keeps a journal of what it's
>> doing,
>> so that interruptions don't break things. So if XFS moves the pointer, it
>> should have a journal entry saying where it was moved from. If the file
>> isnt
>> properly closed, the journal should revert it back to it's old space.
>> Otherwise the whole advantage is lost.
>>
>> Basically, if you have a journaling file system that zeros out the whole
>> file if it's open when you crash, you need a different file system...
>> Because that one's on crack.
>>
>> Course, it may have been an old bug they fixed. :)
>>
>> -Ryan
>>
>> On 7/25/02 4:00 AM, "Phil/CERisE/KG6MBQ" <cerise AT littlegreenmen.armory.com>
>> wrote:
>>
>>> bluebird AT optushome.com.au said:
>>>
>>>> That's interesting, I thought that a major advantage of
>>>> journaling file systems like Reiser & XFS was there ability
>>>> to recover from sudden crashes.
>>>>
>>>> Cheers
>>>>
>>>> Joel
>>>
>>> Well, the problem in the case of XFS is with open files. I don't
>>> know the internals well enough to comment on why they're suddenly
>>> replaced with binary zeros. I suspect it's because when it opens a
>>> file, it preallocates a space for it and sets all the appropriate
>>> pointers to the new place on disk.
>>> They recover faster in the sense that fsck has very little work to
>>> do by comparison. They don't necessarily recover better.
>>> With this in mind, I haven't had that problem with XFS for a good
>>> long while. About 5 months or so of constant use have gone by without
>>> problems.
>>>
>>> -Phil/CERisE
>>>
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>>
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>





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