>I have to do a weekly full backup of a system that has 17 partitions and
>about 500 GB of data. The backup will be done on the weekend, when there are
>few other jobs running. Here are some specs:
>network: 100 MB/sec (12.5 MB/sec)
>SCSI-2 connection : (40 MB/sec)80 MB/sec (two drives)
>Drives: 2 SDLT220's 79.2 GB/hr
>Produce: Netbackup Datacenter 4.5
You also have to take in to consideration the system that houses this data,
and the makeup of the data (it it compressible, few big files vs lots of little
files).
If you have 500GB of data and a 12 hour window, then assuming no compression
one SDLT220 will not back up that amount of data in that window. So you'll
need to use both drives, and feed them each at 11MB/s (to eliminate
shoe-shining)
assuming no compression which means your network must handle 22MB/s. It also
assumes your system can push the data out at 22MB/s as you say you only
have one system to back up.
If your data is compressible, then you can use one drive and keep it fed
at 11-22MB/s (depending on how compressible). If you want to use both drives,
and assuming 2:1 compression you'll need to fed them at 44MB/s.
As has been suggested, you can go to GigE (on the both the client and the
server)
and that will shift the bottleneck away from the network. Then you have to
ensure
that your system can push the data out fast enough to keep the drives streaming.
Mutliplexing is intended to aggregate the network feeds into one to keep the
drive
streaming. Unfortunately you only have one system to back up. If you find
that your
system is able to push out two streams (one to each tape drive) fast enough to
keep the drives streaming you won't need multiplexing. If you find that your
system
pushes a stream out at 7.5MB/s and you can add a second stream at 7.5MB/s (but
you can't
get one stream at 15MB/s) then you'll want to try multiplexing (we have a Novell
system like this).
--
Jeff Bryer bryer AT sfu DOT ca
Systems Administrator (604) 291-4935
Academic Computing, Simon Fraser University
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