You bet! The drives' native speed is rated at 30MByte/sec. Only by virtue
of compression can you get 69MByte/sec! Turns out StorageTek admits that
the HBA on the drive has a maximum throughput rating of 70MByte/sec.
PaulW
www.pbnj-solutions.com IT Solutions That Stick
(216) 533-5708
> -----Original Message-----
> From: Shafto, Eric [mailto:Eric.Shafto AT drkw DOT com]
> Sent: Saturday, April 26, 2003 5:15 PM
> To: 'Paul Winkeler'
> Subject: RE: [Veritas-bu] PCI bus and HBA throughput
>
>
> Was compression on for the tape drives?
>
> -----Original Message-----
> From: Paul Winkeler [mailto:pwinkeler AT pbnj-solutions DOT com]
> Sent: Saturday, April 26, 2003 3:37 PM
> To: jmcdon23 AT csc.com DOT au
> Cc: veritas-bu AT mailman.eng.auburn DOT edu
> Subject: RE: [Veritas-bu] PCI bus and HBA throughput
>
>
> Jim,
>
> That is exactly what we did when we wrote "data" to the
> drives. Let me add that we measured the throughput at the
> host end of the SAN pipe. That is, we used iostat under
> Solaris to watch kb/s numbers over the course of the
> experiment. To recap, we saw:
>
> All zeroes gave us a throughput to a single drive of almost
> 69MByte/sec. Replace the zeroes with data and we only got
> 40MByte/sec. The same pattern appears when writing to three
> drives simultaneously: zeroes add up to ~135MByte/sec; data
> to ~100MByte/sec.
>
> There must just be issues with buffering; interrupt response
> times; and other, higher level protocols that cause this behavior.
>
> PaulW
> www.pbnj-solutions.com IT Solutions That Stick
> (216) 533-5708
>
>
> > -----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
> > jmcdon23 AT csc.com DOT au
> > Sent: Saturday, April 26, 2003 5:44 AM
> > To: Shafto, Eric
> > Cc: veritas-bu AT mailman.eng.auburn DOT edu
> > Subject: RE: [Veritas-bu] PCI bus and HBA throughput
> >
> >
> > Hi
> >
> > Interesting but have you made allowance for hardware
> > compression? Are you measuring the compressability rate of
> > all those "zeroes"? Where is the bottleneck - at the
> > tapehead or compression firmware? Try the same exercise with
> > data that has been already compressed.
> >
> > Regards
> > Jim McDonald
> >
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> >
> > "Shafto, Eric" <Eric.Shafto AT drkw DOT com>@mailman.eng.auburn.edu
> > on 04/26/2003 12:42:50 AM
> >
> > Sent by: veritas-bu-admin AT mailman.eng.auburn DOT edu
> >
> >
> > To: "'Paul Winkeler'" <pwinkeler AT pbnj-solutions DOT com>,
> > "'Vijay Korde'"
> > <vijay_korde AT hotmail DOT com>
> > cc: veritas-bu AT mailman.eng.auburn DOT edu
> > Subject: RE: [Veritas-bu] PCI bus and HBA throughput
> >
> >
> >
> > It would be interesting to see whether the situation
> > improves noticeably with multiple HBAs. Does anyone have
> > some data to share? -----Original Message-----
> > From: Paul Winkeler [mailto:pwinkeler AT pbnj-solutions DOT com]
> > Sent: Friday, April 25, 2003 8:57 AM
> > To: 'Vijay Korde'
> > Cc: veritas-bu AT mailman.eng.auburn DOT edu
> > Subject: RE: [Veritas-bu] PCI bus and HBA throughput
> >
> >
> > Hi Vijay
> >
> > Here is what we found using two other brands of PCI Bus
> > 2Gbit HBA's in SunFire 880's going to T9904B's:
> > 1) To a single drive using 2Gbit HBA's, observed peak
> > ~40MByte/sec, regardless of 33 or 66Mhz bus
> > 2) Writing 3 streams to 3 drives across the same 2Gbit HBA,
> > observed peak ~100MByte/sec regardless of 33 or 66Mhz bus
> > During all tests source data was fully cached in RAM
> > (machine had 8GByte) and no other processes running (machine
> > had 8 CPU's)
> >
> > Wconcluded that the bottleneck was likely in the handling of
> > the SAN protocols across the HBA. Our basis for this
> > conclusion was this:
> > - Writing zeroes (/dev/zero) to a single T9940B drive
> > yielded a rate of 69MByte/sec which is basically the upper
> > limit at which StorageTek claims the drive can take data in;
> > so we know it can go that fast.
> > - Pushing zeroes to 2 drives simultaneously can be done at
> > an aggregate rate of ~130MByte/sec on the 66MHz bus, closer
> > to ~120MByte/sec on the 33Mhz bus.
> > - Going to 3 simultaneous drives with zeroes yields rates of
> > ~138MByte/sec and 129MByte/sec respectivel for the 66MHz and
> > 33Mhz buses. In other words, the bus speed gave the 66Mhz
> > bus a slight edge but hardly worth bothering. It would be
> > very interesting to see what the results look like when you
> > use multiple HBA's simultaneously...
> >
> > My advice: don't hang more than 2 drives of a single HBA.
> >
> > PaulW
> > www.pbnj-solutions.com IT Solutions That Stick
> >
> >
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