tmassey AT obscorp DOT com wrote at about 09:07:04 -0500 on Wednesday, November 
26, 2008:
 > Tino Schwarze <backuppc.lists AT tisc DOT de> wrote on 11/26/2008 01:24:47 
 > PM:
 > 
 > > > > Have you looked at the wait column (last one) in vmstat?
 > > > 
 > > > As in iowait?  Usually the CPU is "100%" used, but much of it is 
 > iowait 
 > > > (~40-60%, IIRC).  Of course, you *expect* that:  I'm I/O bound, after 
 > all, 
 > > > with only a single IDE hard drive...  Also, I'm not using compression, 
 > 
 > > > which is also why I'm not worried about CPU.
 > > 
 > > In my version of vmstat, iowait is not accounted to CPU usage (SuSE
 > > 10.2).
 > 
 > You are right:  I think it's the same on mine (CentOS 5.2).  I'm thinking 
 > of top, where the total CPU is shown as 100%.
 > 
 > But the point holds:  I have lots of unused CPU, even with an *anemic* 
 > EPIA @ 1.2GHz.
 > 
 > 
 > I'm still not sure why people say they need multi-GB of RAM and multi-GHz 
 > CPU's for their BackupPC servers.  I *just* don't see why:  I've got a 
 > pool >600GB on a *tiny* box (without compression, anyway).  Maybe if 
 > you've got >1TB of pool data or multi-millions of files you *might* need a 
 > little more RAM (and I don't think that is the case), but I *still* don't 
 > see why you'd need more than 1GB of RAM, and still no more CPU power. 
 > Again, you need a many-drive RAID array *way* more than you do need CPU or 
 > RAM.
 >  
 > Maybe I'm the only person who's running BackupPC on a box this small.  But 
 > I've got about a *dozen* of these boxes scattered around various clients, 
 > backing up between 10 and 600GB of data.  They *all* run flawlessly.
 > 
Well, there are definitely people running BackupPC on smaller
systems...

A number of people are running BackupPC on small embedded systems like
the d-link DNS-323 NAS device.
That device has only 64MB of RAM of which 16MB is used as a ramdisk!
It uses an arm processor running at about 400-500MHz and I don't think
it even has a floating point processor.

Now at that level, I have found that memory makes a difference when I
try to rsync the pool since rsync compiles a list of all the hard link
inodes and that takes up (some) memory...

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