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Multiplexing can affect restore times under certain conditions.
If you're restoring one file, it may be no big difference. You'll still
have to seek through a fragment to find a the file you need but you'll scan
no more than one fragment.
Where multiplexing costs time is when you have to restore a lot of files
from one member of a multiplexed set. Now you've got to read bunches of
fragments to cull what you need from all the stuff you don't need. If the
servers weren't multiplexed, all of the blocks you read would be needed for
the restore. If you've got a 6-way multiplexed tape, then only a sixth (on
average) of the blocks you read would be of use and you'd have to read
six-times as many blocks to get what you want.
So, in summary, multiplexed jobs cost more time on restoral when you're
restoring large amounts of data.
HTH - M
-----Original Message-----
From: Mark T Wragge [mailto:storage AT ttt DOT ie]
Sent: Friday, September 19, 2003 7:24 AM
To: veritas-bu AT mailman.eng.auburn DOT edu
Subject: [Veritas-bu] will multiplexing effect restore time
I have often been told that the level of multiplexing will effect the
restore time of a client. We are running multiplexing of between 6 to 8
jobs at a time. i would expect the restore time to be slower with this
level of multiplexing than a restore where the multiplexing was set to one.
An engineer has run some tests and reported that there is not much
difference in restore times between the multiplexed and non-multiplexed
backups.
We are a Windows 2000 environment with LTO tape technology.
Regards, Mark
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<DIV><SPAN class=389263714-19092003><FONT face=Arial color=#0000ff
size=2>Multiplexing can affect restore times under certain
conditions.</FONT></SPAN></DIV>
<DIV><SPAN class=389263714-19092003><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=389263714-19092003><FONT face=Arial color=#0000ff size=2>If
you're restoring one file, it may be no big difference. You'll still have
to seek through a fragment to find a the file you need but you'll scan no more
than one fragment.</FONT></SPAN></DIV>
<DIV><SPAN class=389263714-19092003><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=389263714-19092003><FONT face=Arial color=#0000ff size=2>Where
multiplexing costs time is when you have to restore a lot of files from one
member of a multiplexed set. Now you've got to read bunches of fragments to
cull
what you need from all the stuff you don't need. If the servers weren't
multiplexed, all of the blocks you read would be needed for the restore.
If you've got a 6-way multiplexed tape, then only a sixth (on average) of the
blocks you read would be of use and you'd have to read six-times as many blocks
to get what you want.</FONT></SPAN></DIV>
<DIV><SPAN class=389263714-19092003><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=389263714-19092003><FONT face=Arial color=#0000ff size=2>So,
in
summary, multiplexed jobs cost more time on restoral when you're restoring
large
amounts of data.</FONT></SPAN></DIV>
<DIV><SPAN class=389263714-19092003><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=389263714-19092003><FONT face=Arial color=#0000ff size=2>HTH -
M</FONT></SPAN></DIV>
<BLOCKQUOTE dir=ltr style="MARGIN-RIGHT: 0px">
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Tahoma
size=2>-----Original Message-----<BR><B>From:</B> Mark T Wragge
[mailto:storage AT ttt DOT ie]<BR><B>Sent:</B> Friday, September 19, 2003
7:24
AM<BR><B>To:</B> veritas-bu AT mailman.eng.auburn DOT edu<BR><B>Subject:</B>
[Veritas-bu] will multiplexing effect restore time<BR><BR></FONT></DIV>
<DIV><FONT face=Arial size=2>I have often been told that the level of
multiplexing will effect the restore time of a client. We are running
multiplexing of between 6 to 8 jobs at a time. i would expect the
restore time to be slower with this level of multiplexing than a restore
where
the multiplexing was set to one. An engineer has run some tests and
reported that there is not much difference in restore times between the
multiplexed and non-multiplexed backups.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>We are a Windows 2000 environment with LTO tape
technology.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>Regards,
Mark</FONT></DIV></BLOCKQUOTE></BODY></HTML>
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