[dba-Tech] why oh why - big copy bursts

The raid controller is supposed to do that for all the drives under its
control (8 drives).  I would have to check to see if that is enabled or not.
I think it is not up to the drives, but rather the controller. 


John W. Colby
Colby Consulting
www.ColbyConsulting.com 
-----Original Message-----
From: dba-tech-bounces at databaseadvisors.com
[mailto:dba-tech-bounces at databaseadvisors.com] On Behalf Of Gustav Brock
Sent: Friday, February 08, 2008 12:30 PM
To: dba-tech at databaseadvisors.com
Subject: Re: [dba-Tech] why oh why - big copy bursts

Hi John

Perhaps the drives or the controller can be set for (individual) delayed
spin-up?
That could be done for SCSI drives. Not sure about IDE drives.

/gustav

>>> jwcolby at colbyconsulting.com 08-02-2008 18:21 >>>
I am trying to copy a 30 gig file from one computer to another.  Task
Manager shows it "bursting" transmission at 30-40% of network bandwidth for
10 or 20 seconds and then transferring at 3% or so for 10 minutes or so.
While it is bursting it shows "will complete in 10 minutes", when it trails
off it shows "will complete in 160 minutes".  Obviously I want this thing to
finish so I can copy the next file.

Any idea why I would be seeing something like this?

Actually I just took a bathroom break and while thinking about it I may have
come up with the answer.  Software raid 0.  The destination disk is a
software raid 0 drive using three different drives.  Perhaps the destination
computer is caching a bunch of data and then runs out of room to cache more
while it writes the data out to the Raid1 volume.  Which would answer the
question of why I would choose JBOD over RAID0.  The write calculations
required to do RAID0.

On a related note, I decided to test this theory.  I shut off the computer
and started fiddling with the drives.  I decided to just move the drives out
of my WHS box and place them in my SQL Server box and ran square up against
my power supply.  I have a 700 watt supply in there but when I added the
three drives into that box the system would turn on, then right back off.
When I disconnected the new drives the computer turned on just fine.  These
are old western digital caviar 250 gig drives, the kind that came out when
the SATA drives were just entering the market, with a normal power connector
and a SATA connector.  Anyway, my 700 watt supply just wouldn't handle the
load.

Sigh.

I now have 4 of these old WD drives just sitting there.  A terabyte of
identical drives and no home for them.  I guess I will tear open one of my
other boxes and see if I can get them mounted in some other system.

John W. Colby
Colby Consulting
www.ColbyConsulting.com 



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