[ale] why would it take longer to delete a file than to createit?

[John G. Heim]

Doh! Caching... I shoulda thunk of that myself.

But now the question is why does it take so long to write a 1 Gb file?  I 
ran this same test on a half dozn computers and none of them took this long. 
When I ran the command below, with the "conv=fsync" parameter, it took 3 
minutes on my DB server.



----- Original Message ----- 
From: "Greg Freemyer" <greg.freemyer at gmail.com>
To: "Atlanta Linux Enthusiasts - Yes! We run Linux!" <ale at ale.org>
Sent: Tuesday, May 04, 2010 7:22 PM
Subject: Re: [ale] why would it take longer to delete a file than to 
createit?


Try it as:

date; dd if=/dev/zero  of=zero.txt bs=1024 count=1000000 conv=fsync;
date; rm zero.txt; date

note the extra conv=fsync arg

Greg

On Tue, May 4, 2010 at 6:29 PM, John G. Heim <jheim at math.wisc.edu> wrote:
> I have this very slow database server. Today I noticed something strange
> about it. I can create a large file via dd faster than I can delete it.
> Look at the screen cap below... It took just 12 seconds to create the file
> with a million 1K records but it took 36 seconds to delete it. Why would
> that be? I'm running debian lenny with a 2.6.30 kernel. There are 2 500 Gb
> disks in the machine configured as RAID-1. The file system on the disk is
> ext3.
>
> # date; dd if=/dev/zero of=zero.txt bs=1024 count=1000000; date; rm
> zero.txt; date
> Tue May 4 16:59:21 CDT 2010
> 1000000+0 records in
> 1000000+0 records out
> 1024000000 bytes (1.0 GB) copied, 11.7291 s, 87.3 MB/s
> Tue May 4 16:59:33 CDT 2010
> Tue May 4 17:00:09 CDT 2010
>
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