comp.lang.idl-pvwave archive: archive » Re: Writing a very large file

Home » Public Forums » archive » Re: Writing a very large file

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: Writing a very large file [message #57529 is a reply to message #57438]

Mon, 10 December 2007 07:43

Kenneth Bowman
Messages: 86
Registered: November 2006

Member

In article <f169a807-d4a4-4e89-accf-7b07329b12ca@l16g2000hsf.googlegroups.com>,
wlandsman <wlandsman@gmail.com> wrote:

> On Dec 7, 11:50 pm, KenBowman <k-bow...@tamu.edu> wrote:
>
>> What I suspect is happening is the following. The first few images go
>> into cache (memory).
>> Once the cache space is filled, it starts writing the files to disk,
>> which is a much slower process.
>> 6 seconds for a 32 MB file isn't great (~5 MB/s), but maybe you have
>> older hardware or you are writing to
>> a network volume?
>
> Thanks for this and to the others who responded. I do have old
> hardware, so my question should have been "how can the first few
> images be written so quickly?".

Once the data has been written to the cache, which is managed by
the OS, not by IDL, IDL thinks the write is complete and moves on
to the next write.

Memory access is one to two orders of magnitude faster than disk
access. (You have to wait for the platters to rotate, which is a
relatively slow process, electronically speaking.)

Ken Bowman

Report message to a moderator

[Message index]

		Re: Writing a very large file By: Bringfried Stecklum on Sat, 08 December 2007 08:19
		Re: Writing a very large file By: Kenneth Bowman on Fri, 07 December 2007 20:50
		Re: Writing a very large file By: Jim Pendleton, ITT Vi on Fri, 07 December 2007 13:47
		Re: Writing a very large file By: Jean H. on Fri, 07 December 2007 13:23
		Re: Writing a very large file By: pgrigis on Fri, 07 December 2007 12:39
		Re: Writing a very large file By: David Fanning on Fri, 07 December 2007 12:23
		Re: Writing a very large file By: wlandsman on Mon, 10 December 2007 07:24
		Re: Writing a very large file By: Kenneth Bowman on Mon, 10 December 2007 07:43

Previous Topic:	Re: Version Control Conundrum
Next Topic:	SVN Question

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Fri Oct 10 22:50:56 PDT 2025

Total time taken to generate the page: 0.24182 seconds