Performance in Linux DLT1 VS80 tape drives

Steve_Boley@Dell.com Steve_Boley at Dell.com
Wed Apr 10 16:06:00 CDT 2002


This is for info purposes for customers with the DLT1 or VS80 and
performance in linux.

-----Original Message-----
From: Bill Spicer [mailto:bspicer at ccmsi.com]
Sent: Wednesday, April 10, 2002 3:14 PM
To: 'Steve_Boley at Dell.com'
Subject: RE: Partitioning Array


Wow, your right. I can't believe the difference. It went from a 9 hour
backup to a 2 hour backup.

thanks.

bill

-----Original Message-----
From: Steve_Boley at Dell.com [mailto:Steve_Boley at Dell.com]
Sent: Wednesday, April 10, 2002 8:18 AM
To: bspicer at ccmsi.com
Subject: RE: Partitioning Array


No way to verify, it's on by default and apparently there is not a jumper to
enable or disable.  The blocksize will give a huge increase in performance.
We see this not only in linux but also in backup exec and windows it sets
the default blocksize to 1k and is incredibly slow.  You should see the
performance drop to the 4 hour range or less after setting the blocksize.
You should just pass it at the commandline with tar and see what your speed
difference is and then pass at the kernel after verifying that this is your
issue.
steve

-----Original Message-----
From: Bill Spicer [mailto:bspicer at ccmsi.com]
Sent: Wednesday, April 10, 2002 8:12 AM
To: 'Steve_Boley at Dell.com'
Subject: RE: Partitioning Array


Thanks. I may try this.  Our AIX Server (this poweredge is replacing this
server) takes only 5 hours to backup our data. This PowerEdge takes 9 hours.
Doesn't seem right as the old AIX server has an older 15/30 dlt and it's a
two 200 Mhz processor server where as the Dell PowerEdge has a newer 40/80
DLT and it's dual 1.2 Mhz.
Any way to verify compression is on?

-----Original Message-----
From: Steve_Boley at Dell.com [mailto:Steve_Boley at Dell.com]
Sent: Tuesday, April 09, 2002 1:47 PM
To: bspicer at ccmsi.com
Subject: RE: Partitioning Array


See the correction below.
Steve

-----Original Message-----
From: Bill Spicer [mailto:bspicer at ccmsi.com]
Sent: Tuesday, April 09, 2002 1:42 PM
To: 'Steve_Boley at Dell.com'
Subject: RE: Partitioning Array


Where do I put it. Here is my grub.conf

#boot=/dev/sda3                                       
default=0                                             
timeout=10                                            
splashimage=(hd0,2)/grub/splash.xpm.gz                
title Red Hat Linux (2.4.7-10smp)                     
        root (hd0,2)                                  
        kernel /vmlinuz-2.4.7-10smp ro root=/dev/sda8 st=128
        initrd /initrd-2.4.7-10smp.img                


Bill

-----Original Message-----
From: Steve_Boley at Dell.com [mailto:Steve_Boley at Dell.com]
Sent: Tuesday, April 09, 2002 1:26 PM
To: bspicer at ccmsi.com
Subject: RE: Partitioning Array


Hardware compression is on by default.  Here is something you can add to
either your grub.conf kernel parameters or you can pass it during tar to set
the blocksize and will change your backup speed phenomenally.

st=128 for the kernel parameter or tar -cvf /dev/st0 -b 128 /?????

This will make a huge difference in your performance.  Here is a url to a
pdf document at Benchmark's website explaining all the options.

http://www.benchmarktape.com/uploads/support/DLT1_Linux.pdf

Steve

-----Original Message-----
From: Bill Spicer [mailto:bspicer at ccmsi.com]
Sent: Tuesday, April 09, 2002 12:42 PM
To: 'Steve_Boley at Dell.com'
Subject: RE: Partitioning Array

I do have another question though. I'm trying to figure out how to turn on
tape drive hardware compression so when I tar off data it's quicker.   I
don't want to use tar's compression. There should be a setting to set
hardware compression.  Any ideas.  




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