Re: Ext3 vs NTFS performance

Bodo Eggert
2007-05-07T11:22:15Z

Jörn Engel <joern@lazybastard.org> wrote:
> On Fri, 4 May 2007 10:46:10 +0100, Christoph Hellwig wrote:

>> Which means the right place to fix this is samba. Samba just need
>> to intersept lseek and pread/pwrite to never allocate sparse files
>> but do the right thing instead. Now what the right thing would probably
>> be a preallocate instead of writing zeroes, and we need to provide the
>> infrastructure for them to do it, which is in progress currently.
>
> Why do preallocate and not just truncate the file?

If it's done by samba, it's racy. Only the kernel can reliably tell a
write-beyond-eof from a write-before-eof. Either it should unconditionally
turn these preallocation-writes into truncates, or have a flag which will
turn this feature on and which can be used to turn the lseek into a real
preallocation call.

I don't think unconditionally turning these writes into truncate would be
good, it would change the behaviour of dd bs=1 count=$(($n*$BLOCKSIZE+1)).
--
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