Veritas-bu

[Veritas-bu] Slow Performance of Restore

2002-04-11 13:12:23
Subject: [Veritas-bu] Slow Performance of Restore
From: jonw AT n2h2 DOT com (Jon Walton)
Date: Thu, 11 Apr 2002 10:12:23 -0700 (PDT)
The only problems I have seen have been when a switch was set to auto and
a client was set to full-100(or similar example).    As long as both were
set to auto or both were set to full I have never had problems.    Always
using auto takes out a layer of administration, and has worked perfectly
for us.   Sounds like we are the exception though.   This might have to
do with the fact that we use a single switch vendor and 2 or 3 NIC
vendors, so the advice below may very well still apply.

Jon

On Thu, 11 Apr 2002, Larry Kingery wrote:

> It's not half duplex that's so bad (though it is a good bit slower
> than full).  The real problem is when the client and switch disagree
> (this would probably be your 200KB/s, I've usually seen it as
> 150-200). 
> 
> For example, if the switch thinks it can do full, but the client will
> only do half then the switch will end up sending a lot of packets
> (probably TCP ACKs) when the client isn't ready.  These will of course
> fail and have to be retried/retransmitted.  This is when it gets real
> ugly, sending the same thing over and over only makes the problem
> exponentially worse.  
> 
> To repeat what Dave said, "never, ever use auto negotiate".
> 
> 
> Dave High writes:
> > Hi Phil, 
> > 
> > Typically a half duplex NIC runs at between 500 - 800Kb per second depending
> > on your machine and network. At 500Kbps, you are looking at about 1.8 Gig
> > per hour. Sometimes Windows machines at half duplex are even slower than 500
> > Kbps by the way. I have seen rates of 200 - 300 Kbps.. 
> > 
> > It is highly recommended that the NIC be forced to 100Mbit both at the card
> > level, and at the switch level and never, ever use auto negotiate. You would
> > be surprised how many times I have gone onsite to troubleshoot slow backup
> > rates only to have the network guy assure me that Auto Negotiate works just
> > fine, then I have to prove to them that it is stuck in Half Duplex... this
> > usually takes about two days to convince them to double check and test, and
> > it usually clears up the problem.  
> > 
> > Anyway, get the card set to 100Mbit full and retry the restore. You should
> > be able to do between 2 - 4 Megs per second. Use Perfmon to look at NIC
> > rates while it is running, or use the Unix Activity Monitor (Job Monitor) to
> > see how fast the backup is running. You should get nearly the same speed on
> > restores (depending on Multiplexing settings) as you do on backups. 
> > 
> > Other than that, the restore information from NBU is really limited. This
> > has been a pet peeve of mine for the longest time. NBU 4.5 addresses this
> > issue somewhat, but the information is still not as full as the backup
> > information. 
> > 
> > d. 
> > 
> > __________
> > dave high
> > VERITAS Enterprise Consulting
> > 702.683.7733
> >  
> > Unix IS user friendly, it's just VERY picky about who it chooses as friends
> >  
> > 
> > > -----Original Message-----
> > > From: Weber, Philip [mailto:Philip.Weber AT egg DOT com]
> > > Sent: Thursday, April 11, 2002 5:34 AM
> > > To: 'veritas-bu AT mailman.eng.auburn DOT edu'
> > > Subject: [Veritas-bu] Slow Performance of Restore
> > > 
> > > Hi,
> > > 
> > > I am running a restore of an NT client, approx 110 Gb expected; over the
> > > last 8 hours it has done 10 Gb which seems a tad slow.  Can anyone offer
> > > any
> > > hints on how I might troubleshoot this e.g. to check throughput, see how
> > > much is remaining, or improve performance in the future?  I thought I had
> > > seen this topic discussed recently on the list but can't find it on the
> > > archives.
> > > 
> > > ...
> > > 
> > > Since I started writing this email I've discovered that the NT client has
> > > it's 100 MB interface set to Half-Duplex which I guess is what is causing
> > > the problem.  My other questions stand, though, is there any source of
> > > information on restore progress?
> > > 
> > > thanks, Phil
> > > 
> > > PS Solaris 2.6 master & media servers with 1000 MB interfaces, L700 with
> > > DLT
> > > Drives.
> > > 
> > > Phil Weber
> > > IT Infrastructure Unix Systems Engineer
> > > 
> > > Phone: 01384 26 4136
> > > Mobile: n/a
> > > 
> > > 
> > > 
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> -- 
> Larry Kingery 
>          Proofread carefully to see if you any words out.
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