Veritas-bu

[Veritas-bu] question about software compression

2003-03-27 13:40:04
Subject: [Veritas-bu] question about software compression
From: Mark.Donaldson AT experianems DOT com (Donaldson, Mark)
Date: Thu, 27 Mar 2003 11:40:04 -0700
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I run both robots on busses sharing a drive.  In fact, on the one robot
(L3500), it's hardwired that way by the manufacturer (ATL).

There's almost no traffic to the robotic control, it seems a waste to
dedicate an entire bus for a pittance of bytes zipping back and forth.

$.02
-M

-----Original Message-----
From: Jon Walton [mailto:jonw AT n2h2 DOT com]
Sent: Thursday, March 27, 2003 11:28 AM
To: Donaldson, Mark
Cc: 'Marvin Blackburn'; Veritas--ListServer (E-mail)
Subject: RE: [Veritas-bu] question about software compression


I have another question regarding differential SCSI busses.   The guy that
sold me our StorageTek L80 told me never to put a tape drive and a robot
arm on the same SCSI bus.   He could not give me a reason though.
Can someone comment on this?

Thanks,

Jon

On Thu, 27 Mar 2003, Donaldson, Mark wrote:

> 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
> http://mailman.eng.auburn.edu/mailman/listinfo/veritas-bu
>

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<P><FONT SIZE=3D2>I run both robots on busses sharing a drive.&nbsp; In =
fact, on the one robot (L3500), it's hardwired that way by the =
manufacturer (ATL).</FONT></P>

<P><FONT SIZE=3D2>There's almost no traffic to the robotic control, it =
seems a waste to dedicate an entire bus for a pittance of bytes zipping =
back and forth.</FONT></P>

<P><FONT SIZE=3D2>$.02</FONT>
<BR><FONT SIZE=3D2>-M</FONT>
</P>

<P><FONT SIZE=3D2>-----Original Message-----</FONT>
<BR><FONT SIZE=3D2>From: Jon Walton [<A =
HREF=3D"mailto:jonw AT n2h2 DOT com">mailto:jonw AT n2h2 DOT com</A>]</FONT>
<BR><FONT SIZE=3D2>Sent: Thursday, March 27, 2003 11:28 AM</FONT>
<BR><FONT SIZE=3D2>To: Donaldson, Mark</FONT>
<BR><FONT SIZE=3D2>Cc: 'Marvin Blackburn'; Veritas--ListServer =
(E-mail)</FONT>
<BR><FONT SIZE=3D2>Subject: RE: [Veritas-bu] question about software =
compression</FONT>
</P>
<BR>

<P><FONT SIZE=3D2>I have another question regarding differential SCSI =
busses.&nbsp;&nbsp; The guy that</FONT>
<BR><FONT SIZE=3D2>sold me our StorageTek L80 told me never to put a =
tape drive and a robot</FONT>
<BR><FONT SIZE=3D2>arm on the same SCSI bus.&nbsp;&nbsp; He could not =
give me a reason though.</FONT>
<BR><FONT SIZE=3D2>Can someone comment on this?</FONT>
</P>

<P><FONT SIZE=3D2>Thanks,</FONT>
</P>

<P><FONT SIZE=3D2>Jon</FONT>
</P>

<P><FONT SIZE=3D2>On Thu, 27 Mar 2003, Donaldson, Mark wrote:</FONT>
</P>

<P><FONT SIZE=3D2>&gt; What kind of SCSI bus?&nbsp; Differential?&nbsp; =
Two drives per bus should be OK with</FONT>
<BR><FONT SIZE=3D2>&gt; diff.&nbsp; I wonder if HP is giving you =
excuses for poor firmware?&nbsp; Be sure to</FONT>
<BR><FONT SIZE=3D2>&gt; check those drive firmware versions.</FONT>
<BR><FONT SIZE=3D2>&gt;</FONT>
<BR><FONT SIZE=3D2>&gt; Software compression is SSSSlllllooooowwwww and =
puts a measurable effect on</FONT>
<BR><FONT SIZE=3D2>&gt; a client if you usually use multiple =
streams.&nbsp; In my testing, it seems the</FONT>
<BR><FONT SIZE=3D2>&gt; compression algorithm isn't that tight, a =
compressed image on disk will</FONT>
<BR><FONT SIZE=3D2>&gt; recompress with &quot;compress&quot; or =
&quot;gzip&quot; very nicely which shows the algorithm</FONT>
<BR><FONT SIZE=3D2>&gt; is pretty loose.&nbsp; I don't know how well it =
compares to tape compression</FONT>
<BR><FONT SIZE=3D2>&gt; rates, though.</FONT>
<BR><FONT SIZE=3D2>&gt;</FONT>
<BR><FONT SIZE=3D2>&gt; Avoid software compression if you can, =
IMO.</FONT>
<BR><FONT SIZE=3D2>&gt; -M</FONT>
<BR><FONT SIZE=3D2>&gt;</FONT>
<BR><FONT SIZE=3D2>&gt; -----Original Message-----</FONT>
<BR><FONT SIZE=3D2>&gt; From: Marvin Blackburn [<A =
HREF=3D"mailto:mblackburn AT glenraven DOT com">mailto:mblackburn AT glenraven 
DOT com=
</A>]</FONT>
<BR><FONT SIZE=3D2>&gt; Sent: Thursday, March 27, 2003 11:08 AM</FONT>
<BR><FONT SIZE=3D2>&gt; To: Veritas--ListServer (E-mail)</FONT>
<BR><FONT SIZE=3D2>&gt; Subject: [Veritas-bu] question about software =
compression</FONT>
<BR><FONT SIZE=3D2>&gt;</FONT>
<BR><FONT SIZE=3D2>&gt;</FONT>
<BR><FONT SIZE=3D2>&gt; We may have to turn off hardware compression on =
our DLT8000 drives and move</FONT>
<BR><FONT SIZE=3D2>&gt; the compression to NBU.</FONT>
<BR><FONT SIZE=3D2>&gt; We currently run 3.4.3 against a P3000 ATL =
Library.&nbsp; We have two drives on</FONT>
<BR><FONT SIZE=3D2>&gt; the same scsi bus and</FONT>
<BR><FONT SIZE=3D2>&gt; HP is telling us that this may saturate the bus =
and cause hardware errors.</FONT>
<BR><FONT SIZE=3D2>&gt; What kind of performance/time/media =
consequences should I expect.</FONT>
<BR><FONT SIZE=3D2>&gt;</FONT>
<BR><FONT SIZE=3D2>&gt;</FONT>
<BR><FONT SIZE=3D2>&gt;</FONT>
<BR><FONT SIZE=3D2>&gt; ------------------</FONT>
<BR><FONT SIZE=3D2>&gt; Marvin Blackburn</FONT>
<BR><FONT SIZE=3D2>&gt; Systems Administrator</FONT>
<BR><FONT SIZE=3D2>&gt; Glen Raven</FONT>
<BR><FONT SIZE=3D2>&gt; &quot;He's no failure.&nbsp; He's not dead =
yet&quot; --William Lloyd George</FONT>
<BR><FONT SIZE=3D2>&gt;</FONT>
<BR><FONT SIZE=3D2>&gt; =
_______________________________________________</FONT>
<BR><FONT SIZE=3D2>&gt; Veritas-bu maillist&nbsp; -&nbsp; =
Veritas-bu AT mailman.eng.auburn DOT edu</FONT>
<BR><FONT SIZE=3D2>&gt; <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>
<BR><FONT SIZE=3D2>&gt;</FONT>
</P>

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