Fast then SLOOOOW - what's going on?
My main system stores its key data on a large RAID5EE driven from a fast Adaptec RAID card. There are a couple of removable 2TB SATAII drives that store images using ATIH, with incrementals going to alternate drives every second day. (There is also a continuous backup going to a NAS using another product since NONSTOP does not work properly).
This all works fine but there is something strange going on. Sometimes backups happen at 95MB/S, other times at 10MB/S. Seems random which.
I first discovered this when I first started using ATIH 6 months ago. One image backup would be super fast, the next super slow - to the SAME drive. Compression and processor priority settings of course have an effect - but I wind both compression and priority to the max.
In early December I had to rebuild my system from scratch given a motherboard failure. I hoped the problem would go away - and in any case had moved to incremental backups (with limited chain lengths) as a work around. Through unbelievable stupidity in trying to consolidate just one of my backup images, I managed to delete both and so had to create new full initial images from scratch again. So I have been again confronted with this very strange behaviour. One image has been created with an average write speed of just under 100MB/S. (Whew, back to having a fast restore backup, as well as my NAS and offsite NAS mirror... betl AND braces here baby)
The other backup is still going and seems to be klunking along at around 24MB/S now - with very infrequent jumps to 100MB/S. The previous backup (800GB on disk) completed in a few hours - this still has 11 hrs and 650GB to go...
The machine has not been rebooted, no other services activated. So no machine conditions have changed.
Anybody with any clues?
cheers
Rod
p.s. this machine is FAST so CPU overload is not an issue. ATIH is averaging arouynd 15% load on max compression / high priority. As it happens this machine currently holds the world record for the fastest calculation of 0.5, 1, 2.5 and 5 billion digits of PI by a margin of 25% over the previous recordholders... (How USEFUL I hear you gasp) - so it's no slouch...
