Ross,
The old rule of thumb of configuring two DLT7000 drives per SCSI bus was
conceived by using the drive's 2:1 compression ratio of 10MB/sec and
comparing that to the FW SCSI spec of 20MB/sec. The DLT8000 drive
although upgraded to LVD connectivity (LVD SCSI spec of 80MB/sec) has
only an increase of speed of 1MB/sec to 6MB/sec native and 2MB/sec to
12MB/sec with full 2:1 compression. In this case since the LVD bus
supports 80MB/sec then you should be able to support up to six DLT8000
drives per bus.(My solutions implement four max.)
Fibre channel connectivity has essentially moved the bottle neck from
the external I/O Bus to the internal PCI bus. (32-bit,33MHz @ 128MB/sec;
64-bit,33MHz @ 266MB/sec; and 64-bit,66MHz @ 530MB/sec.) By running
multiple FC HBA's on PCI Bus, (E450 supports up to 8) you could
potentially overwhelm the internal PCI buses.
Knowing the above, in your case you will probably be attaching your
DLT7000 drives via a SCSI-Fibre bridge/router to your existing SAN, or to
your NBU Master and Media servers directly. Understanding that each of
the DLT7000 drive's will not run any faster than the maximum of 10MB/sec,
you should be able to theoretically connect up to ten DLT7000 drives
thru a SCSI to Fibre bridge to any one switch port or FC-HBA.
Unfortunately the SCSI to Fibre bridges/routers that I have seen on the
market will only support up to four SCSI's to every Fibre port. You
should therefore be able to connect eight FWD SCSI DLT7000 drives thru
two SCSI-Fibre bridges/routers to the switch or fibre HBA. You must also
take into consideration the CPU and Memory load per tape drive when you
connect these drives to the master and media servers. (This is why we
are anxiously anticipating "TRUE" serverless backup.)
The old CPU/RAM rule of thumb was two DLT7000 drives per 300MHz CPU, and
512MB of RAM. So a maxed out E450 could support up to 8 DLT7000 drives
(4x300MHz CPU's, 8x256MB RAM, 4xFWD SCSI HBA's). Now that the E450
supports the 450MHz CPU's with double the external cache, from 2-MB to
4-MB, we can, and have configured the E450 with a max of 12 DLT7000
drives.
The Bottom Line:
You should be able to connect six of the DLT7000 drives to your E450/E420R
Master configured with 2x450MHz CPU's, and 4x256MB RAM (I would add 512MB
more RAM), and thru a single Fibre HBA without any problem.
Regards,
Michael Gaytan
Solution Engineer
Vangard Technology
> -----Original Message-----
> From: veritas-bu-admin AT Eng.Auburn DOT EDU
> [mailto:veritas-bu-admin AT Eng.Auburn DOT EDU]On Behalf Of parker AT bctm
> DOT com
> Sent: Thursday, June 08, 2000 1:38 PM
> To: veritas-bu AT mailman.eng.auburn DOT edu
> Subject: [Veritas-bu] DLT7000 on FC/AL
>
>
> Hi, folks,
>
> I'm about to dip my toe into the world of Veritas Netbackup (actually,
> for the amount I'm spending, I'll be dipping my whole body, I think!)
>
> I'm stuck on one point - we've got a number of systems on a SAN and want
> to implement NetBack SAN-ready. To that end, we'll be pursuing the
> Shared Storage option drive sharing for all of our tape drives (15 DLT
> 7000s in 3 jukeboxes), and we'll have in total 6 media servers including
> the master, a slave and 4 other big systems (with databases & big file
> systems, etc). Maybe overkill...
>
> Anyway, the question I've got is regarding the hardware - the master is
> going to be either a Sun Enterprise 420R or Enterprise 450, and the
> slave is going to be an Enterprise 220R. Both systems will have 2 CPUs
> and a GB of memory.
>
> What I don't know is how many tape drives I can reasonably expect to
> drive from a single FC/AL PCI card in each server. Obviously, for a
> large part of the time, the other media servers will be using the
> drives, but I'll have about 90 other systems backing up and would like
> to drive the drives @ full speed...
>
> Is there a rule of thumb here? With differential SCSI, the rule was 2
> drives per bus, but nobody seems to know with FC/AL...
>
> Thanks!
>
> Ross
>
>
> --
> Ross Parker | UNIX Sys Admin, Perl and C,
> Systems/Network Admin | Networking and security
> Telus Mobility |
> | Lisp has all the visual appeal of oatmeal
> parker AT bctm DOT com | with fingernail clippings mixed in (Larry
> Wall)
>
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