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July 11th, 2009, 01:13
Originally Posted by Prime Junta View Post
I second hishadow's suggestion. You don't even need the 1 GB network; most of the time the bottleneck will be with disk I/O even on a 10/100 one.
Hmmm… you'd need to have a pretty old HDD for such an extremely poor I/O performance .
100MBit/s = 12.5MByte/s (theoretical maximum without factoring in any network overhead). Just about any modern hard drive can usually read/write at average speeds a good deal north of 60MByte/s (= 480Mbit/s).
So a 1000Mbit network is pretty much required for NAS if you even want to begin to make use of your hard drive performance.

Also, given the numbers you threw out there (5TB ), JemyM, I'm not sure building your own NAS will cut it. It depends on how much data you need to move back and forth.
Incremental backups should cut down significantly on your traffic but if you still need to move hundreds of GBs around then not only do you need a GBit LAN but also a fairly powerful main system (or a lot of time waiting for transfers to finish … which might not be much of a problem if you do backups at night and don't have a problem with your computer and the NAS running while you're sleeping, of course).

The problem with a lot of pre-configured NAS systems like the ones from Buffalo that I linked to above is the poor overall performance of the systems (they usually have a fairly weak CPU so the full potential of the fast disks and GBit network can not unfold).

For example check this link here for a NAS performance test (then select 1000MBps write performance since if you backup you will be writing to the NAS). As you can see, some of the weaker systems barely make it above the speeds that you get with ext. USB 2.0 disks (~15MB/s).

So you might want to consider carefully how much traffic each incremental backup is going to cause. Just a few GByte? OK. Fine. Then get that old box and stuff it full of HDs and a GBit LAN controller. Or still hundreds of GByte? Then it might be better to think about something a lot more powerful or to drop the NAS idea and just go for eSATA disks where it is not much of a problem to get transfer speeds of 60MB/s.
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