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

[Greg Freemyer]

Is that on an idle disk/array?

That would be very slow.

But if its busy serving db queries, its not surprising.

On Wed, May 5, 2010 at 4:45 PM, John G. Heim <jheim at math.wisc.edu> wrote:
> 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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>
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-- 
Greg Freemyer
Head of EDD Tape Extraction and Processing team
Litigation Triage Solutions Specialist
http://www.linkedin.com/in/gregfreemyer
CNN/TruTV Aired Forensic Imaging Demo -
   http://insession.blogs.cnn.com/2010/03/23/how-computer-evidence-gets-retrieved/

The Norcross Group
The Intersection of Evidence & Technology
http://www.norcrossgroup.com