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Dell RAID Battery Causes Slow Backups

Last Updated: 9/6/12

I ran into some very slow Acronis Backup and Recovery 11 backup tasks recently. It affected all my servers, both physical and virtual. I could not figure out why the backup jobs changed from 300+ Mbps to ~110Mbps. Eventually I figured out it was the RAID battery failure on the target server. My backup target is a Dell Server with PERC RAID cards. Apparently having your battery fail switches the virtual disk to write through which is 1/3 the performance of write back. weird huh.

Here is another example (different from the one above) showing how much difference the Write Policy makes on a PERC RAID Card.
server after perc raid force write back.png

Other related articles:
http://agiletesting.blogspot.com/2011/09/slow-database-check-raid-battery.html

http://yo61.com/dell-drac-bbu-auto-learn-tests-kill-disk-performance.html



Keywords: dell PERC raid battery causes slow backup learn cycle