> > What is your i/o subsystem? I have a striped array (raid 0) over two > raid 6 arrays with 7 drives in each array, so effectively I have 10 > spindles. With this I can handle more i/o load than if I only had one > drive.
I'm sure that John knows this, but for the benefit of the OP i'll note that it's a lot more complicated than that, of course. For small writes I might say that you effectively have 2 spindles, and since each small write needs two disk operations I might even say you effectively have only 1 spindle. OTOH for small reads you have 14 spindles. I don't mean to start an argument, and the numbers above are basically pulled out of my butt to make my point. I just want to note for the OP that it gets complicated and you should do more research. > I would expect the throughput of multiple servers backing up in > parallel to be less the the total i/o bandwidth of the disk since each > write will end up moving the heads of the disks to different locations > dropping the effective bandwidth of the disk. Multiple I/O streams can probably make better use of your I/O bandwidth than can a single serial one, unless you are running on low-end hardware like a USB drive. The OS and/or RAID controller and/or disks will reorder requests that come in in parallel so they can be more efficiently performed. Good enough hardware would be a SATA disk with NCQ enabled. NCQ is a function of the disk AND the controller AND the OS, don't assume that all SATA does it. danno -- Dan Pritts, Sr. Systems Engineer Internet2 office: +1-734-352-4953 | mobile: +1-734-834-7224 ------------------------------------------------------------------------------ All of the data generated in your IT infrastructure is seriously valuable. Why? It contains a definitive record of application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-d2d-c2 _______________________________________________ BackupPC-users mailing list BackupPC-users@lists.sourceforge.net List: https://lists.sourceforge.net/lists/listinfo/backuppc-users Wiki: http://backuppc.wiki.sourceforge.net Project: http://backuppc.sourceforge.net/