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[Veritas-bu] Space on tape
2002-08-07 23:06:52
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Space on tapeMark
How about this approach:
1) You know how much data your tape/drive can write un-compressed (e.g.
DLT8000 => 40Gb)
2) Keep writing copies of your full database onto this tape until it filles
up and overflows onto the next tape
3) Knowing how big your database is uncompressed on disk, compared to how
many copies of it fit onto a tape before it filled up the full capacity of
the tape will give you your compressability
This is how I figured a certain 3.2 Tb Oracle database was being compressed
almost 3.5:1 by a set of crummy old DLT7000 drives; not to shabby, eh?
Please let the list know what you uncover; it is always nice to know how
other datasets and drives fare,
PaulW
-----Original Message-----
From: veritas-bu-admin AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-admin AT mailman.eng.auburn DOT edu]On Behalf Of Donaldson,
Mark
Sent: Wednesday, August 07, 2002 6:33 PM
To: Veritasbu (E-mail)
Subject: [Veritas-bu] Space on tape
I'm trying to figure out how may tape blocks are being occupied by a set
of images (we're trying to guess at the compressability of our database and
make inferences to a new one coming online soon).
All NB should know about is blocks moved, right? The drive is doing the
compression.
The only guess I have right now is to do a non-mpx backup to a set of new
tapes, feed the tapes in, then use dd to copy the files to /dev/null and
find out how many blocks are read. Seems like a lot of trouble.
I'm also doing a software compressed backup and finding out how many
blocks are moved that way - it's not apples & oranges but still more like
oranges & lemons - somewhere in the ballpark.
Any other ideas?
-M
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Mark Donaldson - Sr. Systems Engineer
Experian - Denver Colorado
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There are 10 kinds of people in this world, those
that understand binary and those that don't.
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<HTML><HEAD><TITLE>Space on tape</TITLE>
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<DIV><SPAN class=3D050285102-08082002><FONT face=3DArial color=3D#0000ff =
size=3D2>Mark</FONT></SPAN></DIV>
<DIV><SPAN class=3D050285102-08082002><FONT face=3DArial color=3D#0000ff =
size=3D2></FONT></SPAN> </DIV>
<DIV><SPAN class=3D050285102-08082002><FONT face=3DArial color=3D#0000ff =
size=3D2>How=20
about this approach:</FONT></SPAN></DIV>
<DIV><SPAN class=3D050285102-08082002><FONT face=3DArial color=3D#0000ff =
size=3D2>1) You=20
know how much data your tape/drive can write un-compressed (e.g. DLT8000 =
=3D>=20
40Gb)</FONT></SPAN></DIV>
<DIV><SPAN class=3D050285102-08082002><FONT face=3DArial color=3D#0000ff =
size=3D2>2)=20
Keep writing copies of your full database onto this tape until it filles =
up and=20
overflows onto the next tape</FONT></SPAN></DIV>
<DIV><SPAN class=3D050285102-08082002><FONT face=3DArial color=3D#0000ff =
size=3D2>3)=20
Knowing how big your database is uncompressed on disk, compared to how =
many=20
copies of it fit onto a tape before it filled up the full capacity of =
the tape=20
will give you your compressability</FONT></SPAN></DIV>
<DIV><SPAN class=3D050285102-08082002><FONT face=3DArial color=3D#0000ff =
size=3D2>This=20
is how I figured a certain 3.2 Tb Oracle database was being compressed =
almost=20
3.5:1 by a set of crummy old DLT7000 drives; not to shabby,=20
eh?</FONT></SPAN></DIV>
<DIV><SPAN class=3D050285102-08082002><FONT face=3DArial color=3D#0000ff =
size=3D2></FONT></SPAN> </DIV>
<DIV><SPAN class=3D050285102-08082002><FONT face=3DArial color=3D#0000ff =
size=3D2>Please=20
let the list know what you uncover; it is always nice to know how other =
datasets=20
and drives fare,</FONT></SPAN></DIV>
<DIV><SPAN class=3D050285102-08082002><FONT face=3DArial color=3D#0000ff =
size=3D2> PaulW</FONT></SPAN></DIV>
<BLOCKQUOTE dir=3Dltr style=3D"MARGIN-RIGHT: 0px">
<DIV class=3DOutlookMessageHeader dir=3Dltr align=3Dleft><FONT =
face=3DTahoma=20
size=3D2>-----Original Message-----<BR><B>From:</B>=20
veritas-bu-admin AT mailman.eng.auburn DOT edu=20
[mailto:veritas-bu-admin AT mailman.eng.auburn DOT edu]<B>On Behalf Of =
</B>Donaldson,=20
Mark<BR><B>Sent:</B> Wednesday, August 07, 2002 6:33 PM<BR><B>To:</B>=20
Veritasbu (E-mail)<BR><B>Subject:</B> [Veritas-bu] Space on=20
tape<BR><BR></FONT></DIV>
<P><FONT size=3D2>I'm trying to figure out how may tape blocks are =
being=20
occupied by a set of images (we're trying to guess at the =
compressability of=20
our database and make inferences to a new one coming online =
soon).</FONT></P>
<P><FONT size=3D2>All NB should know about is blocks moved, =
right? The=20
drive is doing the compression. </FONT></P>
<P><FONT size=3D2>The only guess I have right now is to do a non-mpx =
backup to a=20
set of new tapes, feed the tapes in, then use dd to copy the files to=20
/dev/null and find out how many blocks are read. Seems like a =
lot of=20
trouble.</FONT></P>
<P><FONT size=3D2>I'm also doing a software compressed backup and =
finding out=20
how many blocks are moved that way - it's not apples & oranges but =
still=20
more like oranges & lemons - somewhere in the ballpark.</FONT></P>
<P><FONT size=3D2>Any other ideas?</FONT> <BR><FONT size=3D2>-M</FONT> =
</P>
<P><FONT=20
=
size=3D2>----------------------------------------------------------------=
-------</FONT>=20
<BR><FONT size=3D2> Mark Donaldson - Sr. Systems =
Engineer</FONT>=20
<BR><FONT size=3D2> Experian - Denver Colorado</FONT> =
<BR><FONT=20
=
size=3D2>----------------------------------------------------------------=
-------=20
</FONT><BR><FONT size=3D2> =
There are=20
10 kinds of people in this world, those</FONT> <BR><FONT=20
size=3D2> that =
understand=20
binary and those that don't. </FONT><BR><FONT=20
=
size=3D2>----------------------------------------------------------------=
-------</FONT>=20
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