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From: Jim Henderson
Subject: Re: missing disk space on server, need help
Date: 9 Nov 2007 15:22:50
Message: <4734c19a@news.povray.org>
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On Fri, 09 Nov 2007 11:46:23 -0300, Nicolas Alvarez wrote:
> Fa3ien escribió:
>> I've run a defrag, which freed 250 Mb.
>
> Defrags free disk space??
I was wondering that myself - disk cleanup would, but not a defrag...
Jim
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On Fri, 09 Nov 2007 16:02:22 +0100, M_a_r_c wrote:
> "Nicolas Alvarez" <nic### [at] gmail isthebestcom> a écrit dans
> le message de news: 473472c5$1@news.povray.org...
>> Fa3ien escribió:
>>> I've run a defrag, which freed 250 Mb.
>>
>> Defrags free disk space??
>
> I am not an expert but maybe if it optimizes disk occupation by filling
> blocks instead of letting empty portions of blocks.
Nope, a block in most* filesystems can only belong to a single file, not
to multiple files, and anything left over in the tail end is lost.
Jim
* I say "most* because I know of at least one filesystem where that isn't
true - NetWare TFS on NetWare 4.x included a feature called "block
suballocation", where the block size for any volume was set to 64KB.
When a file was written out to disk - say, a 65KB file, you would
initially use two full 64KB blocks, and the last KB would leave 63KB of
space wasted. Not long after the write was completed, though, a process
would move that into a special "suballocated" block - AIUI, the
suballocation blocks were of each size possible for the system to handle
- 32, 16, 8, 4, 2, 1 (KB all) and 512 bytes. The file could then be
stored on disc in such a way that the maximum space lost was 511 bytes
for any given file.
The reason this was done was because in early NetWare servers, the admin
had to guess whether there would be lots of little files or not so many
large files in order to pick the proper block size to balance performance
and storage utilisation. BSA removed the need to do that; it was a
feature added at a time when disk storage was fairly expensive, so that +
background compression could save you a ton of money on storage.
Obviously, in a time when a 1 TB external storage device costs ~$350,
that's not so important now.
Jim
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From: Nicolas Alvarez
Subject: Re: missing disk space on server, need help
Date: 9 Nov 2007 17:15:52
Message: <4734dc18@news.povray.org>
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>>> I've run a defrag, which freed 250 Mb.
>>
>> Defrags free disk space??
>
> Theorically, it shouldn't, I'm surprised too. The fact
> is that Windows seen more free space after defrag.
> chkdsk freed the rest !
>
Ah that's why. Defrag does *some* disk checking before starting. I doubt
it does a full chkdsk, or it would have (seemed to) solve your problem.
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Nicolas Alvarez nous apporta ses lumieres en ce 2007/11/09 09:46:
> Fa3ien escribió:
>> I've run a defrag, which freed 250 Mb.
>
> Defrags free disk space??
The OS want to assign a minimum contiguous space to any new or altered file. Any
free space lower than that thresshold is wasted, and often not reported.
Defragmenting consolidate that wasted space at the same tima it put fragmented
files back together.
--
Alain
-------------------------------------------------
Experience hath shewn, that even under the best forms of government those
entrusted with power have, in time, and by slow operations, perverted it
into tyranny.
Thomas Jefferson
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From: Alain
Subject: Re: missing disk space on server, need help (SOLVED with chkdsk)
Date: 9 Nov 2007 22:01:08
Message: <47351ef4$1@news.povray.org>
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Fa3ien nous apporta ses lumieres en ce 2007/11/09 15:11:
> Orchid XP v7 a écrit :
>> Fa3ien wrote:
>>
>>> In short, a good'ol chkdsk /f solved the problem.
>>> I didn't knew that so much empty space could be
>>> erroneously marked as allocated...
>>
>> Woah! o_O
>>
>> That's one unhappy filesystem... heh. Glad it's all fixed now though.
>> (Although you probably ought to find out *why* it did this in the
>> first place...)
>
> I'll check regularly to see if it happens again... Maybe it's related
> to the problems I had with Raid in may. I currently run the server
> without Raid1, because the bad experience showed me that no raid (with
> a daily backup, anyway) is less of a potential hassle than shitty SIS
> software Raid (which is more insecure because it doesn't inform you
> correctly of the real array state).
>
> Fabien.
Faulty raid! Ugly. UGLY! *UGLY!!!!!*
Ready to bet that is was the reason of your vanishing space.
--
Alain
-------------------------------------------------
An organizer for the "Million Agoraphobics March" expressed disappointment in
the turnout for last weekend's event.
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M_a_r_c wrote:
> message de news: 473472c5$1@news.povray.org...
>>> I've run a defrag, which freed 250 Mb.
>> Defrags free disk space??
>
> I am not an expert but maybe if it optimizes disk occupation by filling
> blocks instead of letting empty portions of blocks.
More precisely, if you have a fragmented file taking 3 blocks and
filling them each only 10%, defragging that file will free two blocks.
--
Darren New / San Diego, CA, USA (PST)
Remember the good old days, when we
used to complain about cryptography
being export-restricted?
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Fa3ien wrote:
> WHERE IS THE REST ? (there should be 60 Gb free !)
Besides chkdsk, I was going to suggest making sure nobody has an open,
deleted file that's real big, like some logfile output that someone
deleted the file name but didn't close the program yet that has it open.
--
Darren New / San Diego, CA, USA (PST)
Remember the good old days, when we
used to complain about cryptography
being export-restricted?
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On Sun, 11 Nov 2007 15:26:48 -0800, Darren New wrote:
> More precisely, if you have a fragmented file taking 3 blocks and
> filling them each only 10%, defragging that file will free two blocks.
I don't think that can happen with "standard" files in NTFS or FAT - why
would the OS write to a partial block but not the entire block? Doesn't
make sense to me...
Jim
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Darren New wrote:
> M_a_r_c wrote:
>> le message de news: 473472c5$1@news.povray.org...
>>>> I've run a defrag, which freed 250 Mb.
>>> Defrags free disk space??
>>
>> I am not an expert but maybe if it optimizes disk occupation by
>> filling blocks instead of letting empty portions of blocks.
>
> More precisely, if you have a fragmented file taking 3 blocks and
> filling them each only 10%, defragging that file will free two blocks.
More precisely, how would this situation arrise in the first place?
The allocation engine allocates a full block to a file, and does not
allocate any additional ones until the present ones are full.
As noted elsewhere, in this case it's likely that the defrag partially
corrected the freelists or something. (Remember, the filesystem was
corrupted.)
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Jim Henderson nous apporta ses lumieres en ce 2007/11/12 13:43:
> On Sun, 11 Nov 2007 15:26:48 -0800, Darren New wrote:
>
>> More precisely, if you have a fragmented file taking 3 blocks and
>> filling them each only 10%, defragging that file will free two blocks.
>
> I don't think that can happen with "standard" files in NTFS or FAT - why
> would the OS write to a partial block but not the entire block? Doesn't
> make sense to me...
>
> Jim
Ever heard of "sparse" files?
--
Alain
-------------------------------------------------
To define recursion, we must first define recursion.
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