>From when I used to be pre-sales and tech support for a VAR that sold
different backup solutions:
Run your numbers before you decide on hardware.
It is all about bandwidth.
There is bandwidth you need to consider everywhere.
1. client read speed during the backup session (what else is going on)
2. client network communication speed under that CPU load
3. network issues. ... over the internet in a simple example you often
go:
client -> local switch -> router -> [internet cloud] -> router ->
switch -> backup host
and there can be more layers in there. At one bank I worked for that
was EXACTLY what we saw, only the 'internet cloud' was 'wan', with DS3
at the central site, but T1 at each the client end (37 remote client
sites, some sites had multiple servers). Over a T1 at one client site
(1.44Mbit) the effective throughput rate was considerably less after you
take off protocols, encryption, etc (like .6 of the total bandwidth was
all we could really transport data on).
On your server, again, network NIC bandwidth,
How much are you expecting to recieve at one time?
Do you have enough CPU to drive the NIC full out and do other tasks?
CPU, memory, and backplane bandwidth, to drive the data. (if you can do
DMA and not have the data go through the CPU, that is a good thing).
Do you have enough memory on your backup server (if you swap or page at
all, you do not have enough)?
Are your disk controllers / raid controllers / drives fast enough to
deal with it?
RAID other than RAID 1 has CPU costs to calculate parity or do
comparisons. Good RAID controllers present already raided drives to the
processor, so the CPU does not know/care that there is RAID back there.
But the RAID controller CPU/memory/io speed must be fast enough to keep
up.
On all these rates, you will also find 'burst rates' versus 'sustained
rates'. Burst rates are usually a lot faster and are often quoted in
the sales literature. Snag the information you can from 'white papers'
and from 'product comparisons' in trade rags/journals. Even 'maximum
PC' does interesting non-server raid hardware comparisons sometimes.
This is the BackupPC list, so I won't bore you with the same diatribe
about multi-teer disks and tapes. In short the scenario is the same.
If you would like to send me some information offlist, I would be glad
to help you work through some of it. I am not up on the latest
hardware, but if you have a Dell VAR you use, have THEIR pre-sales SE
(systems engineer) do it and get you the gory detail. Tell them you
need to make it 'run very well' and show me at least 3 different
options. If they are a good VAR, they will be happy to do it, if they
think you are really interested. Talk to their pre-sales SE first, kind
of an interview to see if you believe that 'he knows from where he
speaks'.
I hope this helps. ... Jack
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