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Home -> Community -> Mailing Lists -> Oracle-L -> RE: (Fwd) Re: (Fwd/Oracle) Does NT write to random locations on d
KK - I
definitely agree w/your statement. I'd take computer number
one,
too! And, I did not have the resources <SPAN
class=683552622-12032001>to dig into it
more....i am
sure,
like me, you'd be want to if you could....:)
<FONT face=Arial color=#0000ff
size=2>RM
<FONT face="Times New Roman"
size=2>-----Original Message-----From: Kevin Kostyszyn
[mailto:kevin_at_dulcian.com]Sent: Monday, March 12, 2001 4:56
PMTo: Multiple recipients of list ORACLE-LSubject: RE:
(Fwd) Re: (Fwd/Oracle) Does NT write to random locations on
d
I
don't know Ross, I didn't want to dig to deep into it. The way I see it
is as follows, "hey, that computer is a dual 550 with 10k rpm scsi drives and
a gig of ram. I betcha it would be faster than that piii600 with ide
drives"
<FONT face=Arial
color=#0000ff size=2>I know it's simple minded, but it's kind of
true:)
<FONT face=Arial color=#0000ff
size=2>Kev
<FONT face=Tahoma
size=2>-----Original Message-----From: root_at_fatcity.com
[mailto:root_at_fatcity.com]On Behalf Of Mohan, RossSent:
Monday, March 12, 2001 4:17 PMTo: Multiple recipients of list
ORACLE-LSubject: RE: (Fwd) Re: (Fwd/Oracle) Does NT write to
random locations on d
EP,
I don't see the logic in the last post: "You can't have fast
and best."
First, he doesn't define terms. "Fast"? Is that peak
I/O? Streaming I/O? Single block read? Seek time?
Write time? Come on, trying to reduce this to an
undifferentiated "fast" or "slow" verges on the useless unless one
takes the effort to provide an EXPLICITLY CITED METRIC for
speed. And this fellow didn't.
Second, it's confusing: why is "fast" set against "best" as
though the one is somehow the enemy of the other?
Huh?
Third, it leaves out any discussion of the effect of on-disk
and on-controller cache. (Not to mention
system-level cache.) As far as the application is <FONT
size=2>concerned, it does not see the "disk" alone....it sees controller and
disk cache and disk as an amalgam,
performance-wise....)
Fourth, since WHEN did the choice become forced into "Do you
want a fast hard disk array with lots of fragments,
or a slow disk array with minimal fragments?" Geez,
can I have a slow disk array with lots of fragments?
The only statement I agree with, either logically or from
experience is the bit about OS vendors keeping a bit
secret from the world on their...well, "secret sauce". <FONT
size=2>Sure, you can keep a little bit secret, but come on, folks, it's not
like MS has any other/better/special MoJo than any
other vendor. What? when the aliens landed on the
Redmond campus and revealed their special VASTLY SUPERIOR alien OS
technology, no one else noticed?
The fact is, data access through a system is.....data access
through a system. The *whole* system -- including
caches -- counts. And, logic will tell you that long-stride <FONT
size=2>streaming I/O ( think Oracle Video Server, e.g. ) will work FASTER
and therefore BETTER on a DEFRAGMENTED disk.
(geez)
I guess this one needs someone who really cares enough to
actually test it.
The OS does decide where to put files based on its own
algorythms. This is a big secret with NT (it
is part of their "Intelligence") All OSes have
some form of system for writing data optimally to a <FONT
size=2>disk or drive array. They may give you bits and pieces of how it
works, but the details will remain MS
confidential.
There are a couple of industry wide accepted examples with
no heuristics or intelligence built in.
Generally there is a big tradeoff in optimizing writes and
reads on a hard disk. The more time which is
spent in figuring out where something goes, the
slower disk access is. Do you want a fast hard <FONT
size=2>disk array with lots of fragments, or a slow disk array with minimal
fragments? The choice is yours, you can't have
both fast and best.
Eric
-----Original Message----- Sent:
Friday, March 09, 2001 1:19 PM To: Levinson,
Eric
Until a few days ago I would have agreed entirely with what
you've said. However, about a week or so back,
I ran into a problem with a disk that was so badly
fragmented that Drive Image couldn't create an image of <FONT
size=2>it. I ran Diskkeeper on the drive, in fact several
passes. At least 3 of them were after I
removed ~ half of the files, so that I had around 4Gb <FONT
size=2>free on this 8Gb drive. The fragmentation improved only very
slightly. Several files had in excess of 100
fragments. Since I was preparing for a machine
upgrade anyway, I copied all the files off to <FONT
size=2>another location, formatted the drive, then restored the files
via xcopy. Much to my surprise, while the
fragmentation was much less, I had several large
files that still were badly fragmented. In fact the worst
offender was a 100Mb file which still consisted of
123 fragments. I'm not attempting to disprove
your thinking here, but I'm curious if you have any <FONT
size=2>thoughts on possible reasons for this anomaly?
At 12:16 PM 3/9/2001 -0800, you wrote: <FONT
size=2>>Yes, file fragmentation is a big issue for products that run out
of the OS. >Oracle is kind of an exception,
meaning the files it creates it manages. >Yes,
your database files may be fragmented, but it probably doesn't affect
>your database speed as much as tablespace fragmentation
would, so I would >just ignore it. Oracle
manages how the database files are used pretty <FONT
size=2>>efficiently, even if they are fragmented. <FONT
size=2>> >If you REALLY wanted to defragment
your database files, there is a really >easy
way. Most online defrag utilities (like diskkeeper) simply copies
the >file to another location on the disk, hoping
it will reduce the number of >fragments. On
a nearly full disk it will _increase_ the number of <FONT
size=2>>fragments, so this won't work. <FONT
size=2>> >Best thing would be to back up all
your database files to tape a few times. >
>Delete all the database files from your disks.
Also REMOVE all non >essential files like the
contents of your temp directory, IE cache, etc. <FONT
size=2>> >Defrag your hard disk (if the option
is available in your defragger, choose >"Free
Space Defragmentation") > <FONT
size=2>>Restore your database files to your hard disk. These files
should be >written to your hard disk in a
contiguous fashion by default, if you have a <FONT
size=2>>hunk of open space on your drives. <FONT
size=2>> >Another option would be to use a Raw
file system for Oracle. I am not sure >if
they support this on NT, I know Oracle supports this on Sun,
basically >you don't put a file system on the
drive. You give to Oracle partitions, >and
it manages everything. > <FONT
size=2>>Hope this helps! >Eric
> > <FONT
size=2>>-----Original Message----- >From: Mike
Soultanian [<A
href="mailto:msoultan_at_CSULB.EDU">mailto:msoultan_at_CSULB.EDU]
>Sent: Friday, March 09, 2001 12:01 PM <FONT
size=2>>To: WINNT-L_at_PEACH.EASE.LSOFT.COM <FONT
size=2>>Subject: Re: (Fwd/Oracle) Does NT write to random locations on
disk? > >
size=2>>Later, >mike <FONT
size=2>> >"Eric D. Pierce" wrote:
> > > > -------
To:
From:
size=2>>-------------------------------------------------------------------------->The WINNT-L list is hosted on a Windows NT(TM) machine running L-Soft >international's LISTSERV(R) software. For subscription/signoff info <FONT size=2>>and archives, see <A target=_blank href="http://peach.ease.lsoft.com/archives/winnt-l.html">http://peach.ease.lsoft.com/archives/winnt-l.html .
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