Veritas-bu

[Veritas-bu] question about software compression

2003-03-27 13:25:45
Subject: [Veritas-bu] question about software compression
From: Mark.Donaldson AT experianems DOT com (Donaldson, Mark)
Date: Thu, 27 Mar 2003 11:25:45 -0700
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What kind of SCSI bus?  Differential?  Two drives per bus should be OK with
diff.  I wonder if HP is giving you excuses for poor firmware?  Be sure to
check those drive firmware versions.

Software compression is SSSSlllllooooowwwww and puts a measurable effect on
a client if you usually use multiple streams.  In my testing, it seems the
compression algorithm isn't that tight, a compressed image on disk will
recompress with "compress" or "gzip" very nicely which shows the algorithm
is pretty loose.  I don't know how well it compares to tape compression
rates, though.

Avoid software compression if you can, IMO.
-M

-----Original Message-----
From: Marvin Blackburn [mailto:mblackburn AT glenraven DOT com]
Sent: Thursday, March 27, 2003 11:08 AM
To: Veritas--ListServer (E-mail)
Subject: [Veritas-bu] question about software compression


We may have to turn off hardware compression on our DLT8000 drives and move
the compression to NBU.
We currently run 3.4.3 against a P3000 ATL Library.  We have two drives on
the same scsi bus and
HP is telling us that this may saturate the bus and cause hardware errors.
What kind of performance/time/media consequences should I expect.



------------------
Marvin Blackburn
Systems Administrator
Glen Raven
"He's no failure.  He's not dead yet" --William Lloyd George

_______________________________________________
Veritas-bu maillist  -  Veritas-bu AT mailman.eng.auburn DOT edu
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<P><FONT SIZE=3D2>What kind of SCSI bus?&nbsp; Differential?&nbsp; Two =
drives per bus should be OK with diff.&nbsp; I wonder if HP is giving =
you excuses for poor firmware?&nbsp; Be sure to check those drive =
firmware versions.</FONT></P>

<P><FONT SIZE=3D2>Software compression is SSSSlllllooooowwwww and puts =
a measurable effect on a client if you usually use multiple =
streams.&nbsp; In my testing, it seems the compression algorithm isn't =
that tight, a compressed image on disk will recompress with =
&quot;compress&quot; or &quot;gzip&quot; very nicely which shows the =
algorithm is pretty loose.&nbsp; I don't know how well it compares to =
tape compression rates, though.</FONT></P>

<P><FONT SIZE=3D2>Avoid software compression if you can, IMO.</FONT>
<BR><FONT SIZE=3D2>-M</FONT>
</P>

<P><FONT SIZE=3D2>-----Original Message-----</FONT>
<BR><FONT SIZE=3D2>From: Marvin Blackburn [<A =
HREF=3D"mailto:mblackburn AT glenraven DOT com">mailto:mblackburn AT glenraven 
DOT com=
</A>]</FONT>
<BR><FONT SIZE=3D2>Sent: Thursday, March 27, 2003 11:08 AM</FONT>
<BR><FONT SIZE=3D2>To: Veritas--ListServer (E-mail)</FONT>
<BR><FONT SIZE=3D2>Subject: [Veritas-bu] question about software =
compression</FONT>
</P>
<BR>

<P><FONT SIZE=3D2>We may have to turn off hardware compression on our =
DLT8000 drives and move</FONT>
<BR><FONT SIZE=3D2>the compression to NBU.</FONT>
<BR><FONT SIZE=3D2>We currently run 3.4.3 against a P3000 ATL =
Library.&nbsp; We have two drives on</FONT>
<BR><FONT SIZE=3D2>the same scsi bus and</FONT>
<BR><FONT SIZE=3D2>HP is telling us that this may saturate the bus and =
cause hardware errors.</FONT>
<BR><FONT SIZE=3D2>What kind of performance/time/media consequences =
should I expect.</FONT>
</P>
<BR>
<BR>

<P><FONT SIZE=3D2>------------------</FONT>
<BR><FONT SIZE=3D2>Marvin Blackburn</FONT>
<BR><FONT SIZE=3D2>Systems Administrator</FONT>
<BR><FONT SIZE=3D2>Glen Raven</FONT>
<BR><FONT SIZE=3D2>&quot;He's no failure.&nbsp; He's not dead yet&quot; =
--William Lloyd George</FONT>
</P>

<P><FONT =
SIZE=3D2>_______________________________________________</FONT>
<BR><FONT SIZE=3D2>Veritas-bu maillist&nbsp; -&nbsp; =
Veritas-bu AT mailman.eng.auburn DOT edu</FONT>
<BR><FONT SIZE=3D2><A =
HREF=3D"http://mailman.eng.auburn.edu/mailman/listinfo/veritas-bu"; =
TARGET=3D"_blank">http://mailman.eng.auburn.edu/mailman/listinfo/veritas=
-bu</A></FONT>
</P>

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