I believe Stan meant adv_file devices or VTL (virtual tape library that's 
actually disk).

The number of channels on the FC-SCSI bridge will vary by model.  The one 
we used to use from Chaparral had a single FC input with three SCSI 
channels outbound.  The bridges in our current library have 1 FC + 2 SCSI.

Jeff Mery - MCSE, MCP
National Instruments

-------------------------------------------------------------------------
"Allow me to extol the virtues of the Net Fairy, and of all the fantastic
dorks that make the nice packets go from here to there. Amen."
TB - Penny Arcade
-------------------------------------------------------------------------



Olaf Zaplinski <o.zaplinski AT BROADNET DOT DE> 
Sent by: Legato NetWorker discussion <NETWORKER AT LISTSERV.TEMPLE DOT EDU>
07/21/2006 09:07 AM
Please respond to
Legato NetWorker discussion <NETWORKER AT LISTSERV.TEMPLE DOT EDU>; Please 
respond to
Olaf Zaplinski <o.zaplinski AT BROADNET DOT DE>


To
NETWORKER AT LISTSERV.TEMPLE DOT EDU
cc

Subject
Re: [Networker] Slightly off-topic query






Thanks for your answers!

Stan Horwitz wrote:
 > I am not sure, but your environment is crying out for a block-level
 > disk-to-disk backup solution.

Block level? Do you mean rawasm?

Anyway, disk-to-disk-to-tape is what we are doing here, so network 
throughput would not be the major issue. But when we stage to tape we must 

ensure that all tape drives are fed with enough data.


Jeff Mery wrote:
> Let's say I just have one LTO2 drive doing Windows backups:   30MB/sec 
> native * 1.5 compression = 45MB/sec; add 6.75 MB for safety net (round 
to 
> 7MB) and we have 52MB/sec that I need to push to this drive.  If this 
> drive is doing Oracle, I would have (30MB/sec * 3 compression) = 
90MB/sec; 
> add 15 MB for safety net and we have 105MB/sec.  Does that seem high for 
a 
> 30MB/sec device?  Absolutely.  Remember that the native drive speed is 
the 
> fastest that the heads can put data onto the media - period.  At 3:1 
> compression, I need to push 90MB of data to keep the drive at 30MB =).

Hmm... I think we should keep the old server and get a new disk array. 
30-45 
MB/s is the usual maximum that I have seen on the LTO2 drive since now (we 

have it for 3 weeks now). When other drives are staging too, it drops to 
12-15 MB/s.

> Just because you have 2Gb FC coming in, doesn't mean 
> you'll be able to push that through SCSI on the other end.  This is 
> especially true when mixing drive types as the entire SCSI channel will 
> drop to the speed of the slowest device.

Oh, so all four drives would be connected to a single SCSI channel? I 
thought that each connector on such a bridge would be an isolated SCSI 
channel.

> I would also recommend dedicating one FC card/port for tape and a second 

> one for disk.

Sounds reasonable.

> Finally, be sure this 1U server has the horsepower to move all this 
data. 
> They don't in our environment so we have to use 4 CPU systems.

*sigh* I'll have to ask my boss for all this... it will be quite 
expensive.

Olaf

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