Adding a 0.5TB Drive and Default DMA Settings

Yesterday, I went to Fry's again to pick up a Big Disk for my server (the one hosting my book's site and this blog). I was happily surprised to find that they had a sale, ending that day, on Seagate 500GB hard drives, with a 5-year warranty, no less. Normally $300, they were on sale for $200. I hadn't even noticed the sale price, and was considering a different brand (I don't have a great feeling about Seagate, but then, I don't have a great feeling about any hard disk manufacture, but have not had any experience yet, good nor bad, with Hitachi, so was considering their 500GB drive for $270) when the sales guy noticed I was looking at 500GB drives and pointed out the sale. I appreciated that.

It was a fully-boxed disk, not an unboxed bulk OEM version, so has a 5-year warranty. Other brands I noticed had a 3-year warranty. The difference doesn't seem so great to me, though, since three years from now, I'm sure a 0.5TB disk like this will be cheap, and considered to be on the small side of things.

Anyway, I bought it and drove to the ISP to install it. (I should note that my hosting is complimentary of Peak Web Hosting with the network managed by Peak Web Consulting, for which I remain ever grateful.)

I installed the drive and put the most-excellent Reiser file system (reiserfs) onto it. “df -h” showed a size of 460G. Sweet. I then started a copy of 70 gig worth of data from a drive on loan from a friend. I knew it would take a while, so I whipped up a little Perl app to watch the drives, calculate running copy speed, and predict when it would complete.

It was slow going. The copy was running at less than two megabytes/second. Ugh.

I checked out the disk settings with hdparm (“hdparm -i /dev/hdc”) and noticed that DMA was not turned on. I turned it on (“hdparam -d1 /dev/hdc”) and saw the copy speed go up by over 11×.

An 11× speedup via one setting change.

I don't know whether the lack of DMA by default is the drive's fault, the controller's fault, the motherboard's fault, or the OS's fault, but because DMA is turned on for the other drives by default, I suspect it's the drive. So be careful to check that DMA is on after installing a new IDE (aka “ATA” aka “PATA”) drive. (It's not an issue with drives using the more modern SATA interface.)


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