Summary: Which is faster: SDLT or 100BT Ethernet Full Duplex?

Thanks to Kevin, Brian, Sam, Matthew.

There will be very few servers on a private switched network and the 
application will have to be shut down once per week for the big backup, 
the network will be quiet so no contention.

SDLT appears to be faster than 100BT! There is a new version which is 
even faster. I guess to beat it will require gigabit Ethernet.

Thanks for your help. 

Richard


============
11 MBytes/sec = 88Mbits/sec < 100Mbits/sec 

or 

100Mbits/sec = 12.5MBytes/sec > 11MBytes/sec 

The network would be quicker, however I know the network has additional 
overhead, so you  will not see 12.5MB/s, 
and I would assume the tape would also have some overhead. 

If "less efficient" means more overhead, I would say the network.  
If "less efficient" means  slower, I would 
think the tape.  If you are copying the data to the box with the tape 
drive than this is a  moot point since 
all backup will be local. 

Brian 

==========
test your network speed. I didn't get near 90% bandwidth throughput 
speeds
when I was moving 30G. faster than rcp was ufsdump | ufsrestore... but 
that
only worked close to line speed if I was running 8 or more 
simultaneously.
One process ran at much slower than line speed.

YMMV. good luck.

Kevin 
===========

> Sun on their website claim 11 Mbytes (not bits) per second for Super
> DLT.

The third-party external SDLT connected to one of my E250s gives me 
about
6Mbytes/sec average for the biggest (55Gb or so) partition it backs up.
> 11 MB per second appears to me to be faster than I could expect 
network
> copies to run at. Our network is 100BaseT Full Duplex. I would copy
> the data using whatever is fastest be it ftp, scp, rcp or NFS.

The `dd' that this (local) partition is backed up with, under the hood,
does that 55Gb in about 160 minutes. That's about 50Mbits/sec average, I
reckon.
> If I copied say 40GB to SDLT tape or over the network should I expect
> about 1 hour in either case?

I reckon it depends mostly on what else any network components in the 
path
might be doing at the time. When I look at my network logs while a 
backup
is in progress, I can spot other activity on, say a LAN switch that has 
a
backup client and server talking to each other as a dip in the traffic
between that client and server. If you can guarantee to be able to
saturate client and server interfaces and don't have to put up with
servicing other traffic with the network components involved, you may 
well
win with over-the-net copying, but the one thing a local SDLT will give
you is repeatability, even if it is somewhat slower.


Sam 


My email addresses are:
 "Richard_Mackerras" in the domain "MySun.Com"
 "Richard.Mackerras" in the domain "AvonAndSomerset.Police.UK"

----- Original Message -----
From: "Richard Mackerras" <richard_mackerras@mysun.com>
Date: Thursday, October 31, 2002 2:16 pm
Subject: Which is faster: SDLT or 100BT Ethernet Full Duplex?

> Hi,
> 
> Sun on their website claim 11 Mbites (not bits) per second for 
> Super 
> DLT. 
> 
> 11 MB per second appears to me to be faster than I could expect 
> network 
> copies to run at. Our network is 100BaseT Full Duplex. I would 
> copy the 
> data using whatever is fastest be it ftp, scp, rcp or NFS. 
> 
> If I copied say 40GB to SDLT tape or over the network should I 
> expect 
> about 1 hour in either case?
> 
> Which is going to be less efficient, Ethernet? 
> 
> TIA,
> 
> Richard
> 
> 
> My email addresses are:
> "Richard_Mackerras" in the domain "MySun.Com"
> "Richard.Mackerras" in the domain "AvonAndSomerset.Police.UK"
> _______________________________________________
> sunmanagers mailing list
> sunmanagers@sunmanagers.org
> http://www.sunmanagers.org/mailman/listinfo/sunmanagers
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