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I've actually heard this before as well (or maybe read it somewhere), but
it is only when the drive becomes available...
In an MPX situation, when one job ends, if another queued job can MPX onto
the same tape (storage unit, retention, MPX values allow it) that queued
job will go active instead of the higher priority job. The fact of the
matter is, during most backup windows, there is almost always a job that
can do this and dozens or even hundreds of jobs can complete this way
before the tape drive actually becomes available for a higher priority
job.
This occurs, not only with restores, which are supposedly a priority over
backups, but also with higher priority backups.
It appears that there is a fundamental flaw in the way priorities are
handled, but how do you do it better? I don't know if I would want a
drive with 5 active jobs MPX'ing to it, to go down to 4, 3, 2, 1 until it
is 0 and becomes available (this could take some time, at which point the
drive is working at partial capacity and queued jobs are just sitting
there), just because a higher priority job is queued up.
Stopping (or pausing) a backup and making the drive available to be used
for a restore and then continuing a backup later is nice, but it doesn't
address the issue with lower priority backups going active over higher
priority backups if the higher priority backup doesn't use the same
storage unit or retention or doesn't have a high enough MPX value.
Leaving unallocated (from a Storage Unit's perspective) tape drives isn't
always an option in an SSO environment with a high percentage of SAN Media
Servers.
- Scott
"Goldfarb, Josh" <Josh.Goldfarb AT blackrock DOT com>
Sent by: veritas-bu-admin AT mailman.eng.auburn DOT edu
09/11/2003 07:12 AM
To: <veritas-bu AT mailman.eng.auburn DOT edu>
cc:
Subject: [Veritas-bu] RE: Veritas-bu digest, Vol 1 #2498 - 1 msg
IT is my understanding that a restore is the highest priority. If all
your drives are taken from backups it will grab the next available
drive.
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Sent: Wednesday, September 10, 2003 1:02 PM
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Subject: Veritas-bu digest, Vol 1 #2498 - 1 msg
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Today's Topics:
1. Re: Prioritizing Restores over Backups in 4.5 (Wayne T Smith)
--__--__--
Message: 1
Date: Wed, 10 Sep 2003 09:38:34 -0400
From: Wayne T Smith <WTSmith AT maine DOT edu>
To: veritas-bu AT mailman.eng.auburn DOT edu
Subject: Re: [Veritas-bu] Prioritizing Restores over Backups in 4.5
Hart, Charles wrote, in part:
> Oh.. I can't hold it in. I'm a fairly new user to Netbackup 4.5FP#,
> have been using TSM for a couple years, and I find this troubling. In
the TSM world Restores Always take precedence. If another task is using
a drive in TSM, TSM will make a drive available, then once the restore
is complete TSM will know where it left off on the prior task.
>
> I feel like I've just traded in my Cadillac for a KIA.....
You did! Join the club. Nothing is perfect, though that Cadillac was
pretty good. ;-)
cheers, wayne
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<br><font size=2 face="Arial">I've actually heard this before as well (or maybe
read it somewhere), but it is only when the drive becomes available...</font>
<br>
<br><font size=2 face="Arial">In an MPX situation, when one job ends, if
another queued job can MPX onto the same tape (storage unit, retention, MPX
values allow it) that queued job will go active instead of the higher priority
job. The fact of the matter is, during most backup windows, there is
almost always a job that can do this and dozens or even hundreds of jobs can
complete this way before the tape drive actually becomes available for a higher
priority job.</font>
<br>
<br><font size=2 face="Arial">This occurs, not only with restores, which are
supposedly a priority over backups, but also with higher priority
backups.</font>
<br>
<br><font size=2 face="Arial">It appears that there is a fundamental flaw in
the way priorities are handled, but how do you do it better? I don't know
if I would want a drive with 5 active jobs MPX'ing to it, to go down to 4, 3,
2, 1 until it is 0 and becomes available (this could take some time, at which
point the drive is working at partial capacity and queued jobs are just sitting
there), just because a higher priority job is queued up.</font>
<br>
<br><font size=2 face="Arial">Stopping (or pausing) a backup and making the
drive available to be used for a restore and then continuing a backup later is
nice, but it doesn't address the issue with lower priority backups going active
over higher priority backups if the higher priority backup doesn't use the same
storage unit or retention or doesn't have a high enough MPX value.</font>
<br>
<br><font size=2 face="Arial">Leaving unallocated (from a Storage Unit's
perspective) tape drives isn't always an option in an SSO environment with a
high percentage of SAN Media Servers.</font>
<br>
<br>
<br><font size=2 face="Arial">- Scott</font>
<br>
<br>
<br>
<br>
<table width=100%>
<tr valign=top>
<td>
<td><font size=1 face="sans-serif"><b>"Goldfarb, Josh"
<Josh.Goldfarb AT blackrock DOT com></b></font>
<br><font size=1 face="sans-serif">Sent by: veritas-bu-admin AT
mailman.eng.auburn DOT edu</font>
<p><font size=1 face="sans-serif">09/11/2003 07:12 AM</font>
<br>
<td><font size=1 face="Arial"> </font>
<br><font size=1 face="sans-serif"> To:
<veritas-bu AT mailman.eng.auburn DOT edu></font>
<br><font size=1 face="sans-serif"> cc:
</font>
<br><font size=1 face="sans-serif"> Subject:
[Veritas-bu] RE: Veritas-bu digest, Vol 1 #2498 - 1
msg</font></table>
<br>
<br>
<br><font size=2 face="Courier New">IT is my understanding that a restore is
the highest priority. If all<br>
your drives are taken from backups it will grab the next available<br>
drive. <br>
<br>
<br>
-----Original Message-----<br>
From: veritas-bu-request AT mailman.eng.auburn DOT edu<br>
[mailto:veritas-bu-request AT mailman.eng.auburn DOT edu] <br>
Sent: Wednesday, September 10, 2003 1:02 PM<br>
To: veritas-bu AT mailman.eng.auburn DOT edu<br>
Subject: Veritas-bu digest, Vol 1 #2498 - 1 msg<br>
<br>
<br>
Send Veritas-bu mailing list submissions to<br>
veritas-bu AT
mailman.eng.auburn DOT edu<br>
<br>
To subscribe or unsubscribe via the World Wide Web, visit<br>
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or, via email, send a message with subject or body 'help' to<br>
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mailman.eng.auburn DOT edu<br>
<br>
You can reach the person managing the list at<br>
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<br>
When replying, please edit your Subject line so it is more specific than<br>
"Re: Contents of Veritas-bu digest..."<br>
<br>
<br>
Today's Topics:<br>
<br>
1. Re: Prioritizing Restores over Backups in 4.5 (Wayne T Smith)<br>
<br>
--__--__--<br>
<br>
Message: 1<br>
Date: Wed, 10 Sep 2003 09:38:34 -0400<br>
From: Wayne T Smith <WTSmith AT maine DOT edu><br>
To: veritas-bu AT mailman.eng.auburn DOT edu<br>
Subject: Re: [Veritas-bu] Prioritizing Restores over Backups in 4.5<br>
<br>
Hart, Charles wrote, in part:<br>
<br>
> Oh.. I can't hold it in. I'm a fairly new user to Netbackup 4.5FP#,
<br>
> have been using TSM for a couple years, and I find this troubling.
In<br>
the TSM world Restores Always take precedence. If another task is
using<br>
a drive in TSM, TSM will make a drive available, then once the restore<br>
is complete TSM will know where it left off on the prior task.<br>
> <br>
> I feel like I've just traded in my Cadillac for a KIA.....<br>
<br>
You did! Join the club. Nothing is perfect, though that Cadillac
was <br>
pretty good. ;-)<br>
<br>
cheers, wayne<br>
<br>
<br>
<br>
--__--__--<br>
<br>
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