Performance in Linux DLT1 VS80 tape drives

Michael E Brown michael_e_brown at dell.com
Thu Apr 11 11:58:00 CDT 2002


dd? Are you referring to the Unix 'dd' command? If this is the case, I
certainly hope that you are not using the unix dd command to do your
filesystem backups. This is a serious mistake. dd will most certainly
never produce a consistent filesystem snapshot. tar and/or dump/restore
are the built-in tools for doing this, and will produce a restorable
backup. Even better would be add-on package such as Amanda, Backup-exec,
Legato, etc which have finer-grained backup options.

Also, what do you mean by "interactive restore capability"? I was not 
aware of dd having an interactive anything... I'm a bit confused on this 
point.
--
Michael


On Thu, 11 Apr 2002, Roddy McColl wrote:

> 
> Hope this isn't too naive, but its a two part question.
> 
> 1) Will the grub.conf change (st=128) affect the working of the dd command?
> 2) This doc below describes using tar for backup. Does anyone out there use
>    dd? I don't understand why tar would be preferable to dd since
>    there is no interactive restore capability with tar.
> 
> TIA
> 
> -roddy
> 
>        -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
>          Roddy McColl PhD      roddy at mri.swmed.edu
> 	 UT Southwestern            (214) 648-2910
> 	 http://www-mri.swmed.edu/homes/roddy.html
>        -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
> 
> 
> > 
> > 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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> 
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> 

-- 
Michael E. Brown, RHCE, MCSE+I, CNA
Dell Linux Solutions
http://www.dell.com/linux

  If each of us have one object, and we exchange them,
     then each of us still has one object.
  If each of us have one idea,   and we exchange them,
     then each of us now has two ideas.





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