Hi, all!

We installed a disk based backup system a couple of months
ago, because we have been hitting the capacity of our tape
changer on almost every nightly run - and we did not even
backup everything. So a new system was in called for.

The backup server features 2 GB of main memory, a reasonably
fast CPU (2.8 GHz Xeon) and 4 TB of storage in two separate
RAID 5 sets.

In our primary Amanda instance we have 200 GB sized vtapes,
200 GB of holding disk space (holding disk and vtapes on different
RAID sets). The compressed nightly backup data are frequently less
than 100 GB and never more than 130 GB. We have 95 DLEs on 35 hosts.

When we started, we had only one RAID set, so I did not configure
a holding disk. With the current architecture of Amanda this
essentially means "inparallel 1". The backups took about 20 hours
after all 95 DLEs were added.

Since we needed more disk space and a second Amanda instance anyway,
I doubled the disk space by buying more disks and ended up with two
identical RAID 5 sets. With the machine we have there have to be
two sets, because there are two separate controllers connected
to 6 SATA disks each.

This bought us a holding disk and parallelism. So I hoped. Now
the backups take 12 to 13 hours per nightly run. Sometimes 8
if there is not much to backup.

The config changes I made to achieve this were:

inparallel 10
maxdumps 1
netusage 12500 kbps

holdingdisk hd1 {
    directory "/raid1/holdingdisk"
    use 204800 mbytes
}

But I'm not satisfied, yet ;-)

Example:

Original Size (meg)    218907.0
Avg Dump Rate (k/s)      1158.9
Tape Time (hrs:min)        1:08

This run took about 13 hours. About one hour of this is tape time.
So the rest is needed to transfer the data from the clients to the server.

Since the server doesn't do anything but backups, I'd like to max
out CPU and network usage on the server. Therefore I compress everything on
the server besides 4 hosts that are located in a remote datacenter where
we have to pay for data transferred.

All other backup clients have a dedicated 100 Mbit/s connection to the
backup server. My goal is to have the network almost saturated.
If you use a calculator, then with a 100 Mbit/s network the 200+
GB of the above run should be transferred in less than 5 hours.
If I didn't make a stupid mistake here.

The CPU compressing the data runs at about 60% idle when busy compresing
data and almost completely idle the rest of the time.

So how do I go about identifying the bottlenecks? Just crank up
"inparallel"? It must be possible to get down to, say, half of the
13 hours, IMHO.


Thanks a lot for any hints,
Patrick
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