Networker

Re: [Networker] Block Size Questions

2003-01-28 16:08:48
Subject: Re: [Networker] Block Size Questions
From: Terry Lemons <lemons_terry AT EMC DOT COM>
To: NETWORKER AT LISTMAIL.TEMPLE DOT EDU
Date: Tue, 28 Jan 2003 16:08:13 -0500
Hi Joel

I believe that, if you set the NSR_DEV_BLOCK_SIZE_MSG=YES environment
variable, NetWorker will generate messages showing the default values for
each supported drive type when nsrmmd starts.  In my experience, these have
appeared in the nwadmin messages window, as well as being written to
daemon.log.

tl


-----Original Message-----
From: Joel Fisher [mailto:jfisher AT wfubmc DOT edu]
Sent: Tuesday, January 28, 2003 3:58 PM
To: lemons_terry AT emc DOT com
Cc: NETWORKER AT LISTMAIL.TEMPLE DOT EDU
Subject: RE: [Networker] Block Size Questions


Hey Terry,

Thanks for pointing out where I can find out the current block size of a
tape(RTFM):-).  As it turns out after running a 'scanner -v' on the tape
that gave the "Block size is 80 bytes not 262144 bytes" message while
labeling, the block size was set to 262144.  That must just be an
informational message.

I spoke with STK again and my st.conf is okay. AFAIK st.conf doesn't play
into block size.  Unless I suppose if you don't have any entries for your
drive type. 

So I guess the only thing I'm still unsure about is what block size to use
for the DDS drives.  So since by default Legato picked 256K, are you saying
that is the best block size for 9940B drives on Windows and Solaris?  Is
there some way to take a look at the device table you're talking about?  I
looked around the Legato website but didn't see anything along these lines.

TIA,

Joel

-----Original Message-----
From: lemons_terry AT emc DOT com [mailto:lemons_terry AT emc DOT com] 
Sent: Tuesday, January 28, 2003 11:23 AM
To: Joel Fisher
Cc: NETWORKER AT LISTMAIL.TEMPLE DOT EDU
Subject: RE: [Networker] Block Size Questions

Hi Joel

You mentioned: 

"These drives will be used for DDS with a WIN2K system so I need to set a
block size.  Any suggestion for the best block size for compatibility
and performance?  I haven't been able to find much info on WIN2K max
block size, so if anyone knows where I can find that type of data I
would appreciate it."

First, you MUST make sure that all systems using the same media also use the
same block size when using that media.  NetWorker already does this, in that
NetWorker has a table that defines (in Legato's experience) the best block
size for each of the media types NetWorker supports.  So, this answers your
"best block size for performance" question.  NetWorker uses the same device
table on ALL of its platforms (Solaris, Windows, etc.).  That's how
NetWorker ensures that it can use a piece of media on multiple platforms.
BUT the operating systems ALSO need to do their part (more on this below).

In the message, "Block size is 80 bytes not 262144 bytes", you can see that
NetWorker tried to use a block size of 262144 (= 256KB).  This is
NetWorker's default block size for your tape device.  Other devices have
different NetWorker-specified block sizes.  There is a section in the
NetWorker Administrator's Guide that talks about how to display and change
these optimal block sizes.

The other part of the story is the operating system and its drivers.  Even
though NetWorker always uses the same block size, the operating system may
not.  Apparently, your Solaris system is using a block size of 80 bytes for
this device.  As others have suggested, you need to modify Solaris'
behavior, probably by adjusting st.conf.

On Windows, you may find that your FC or SCSI HBA does not allow 256 KB
writes by default.  If it doesn't, adjust it to do so.  If it can't, then
you'll need to figure out the maximum value, and use that on all of your
systems; that's where the NetWorker block size environment variable may need
to be used.

Hope this helps!
tl

Terry Lemons
CLARiiON Applications Integration Engineering
        EMC²            
where information lives

4400 Computer Drive, MS D239
Westboro MA 01580
Phone: 508 898 7312
Email: Lemons_Terry AT emc DOT com

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