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As A Hard Drive Gets Full, How Much Speed Is Lost?

Originally posted February 9th, 2002
Updated February 15th, 2002, with Ultra ATA-133 controller times and a couple of "tweaks" to make the ATA-66 run faster.
rob ART morgan, Bare Feats Mad Scientist

I saw a graph on StorageReview.com showing how the speed of each test drive dropped off progressively as the "end" of each drive was reached. I don't have any benchmark software to automatically measure that but I did something almost as good. I reformatted two of the fastest Ultra ATA drives tested recently and created two partitions. The first partition would include the fastest part of the disk or "beginning" and the second partition would consist of the last 5 GB's or slowest part of the disk or "end."

I ran my "duplicate one very large document" test and the QuickBench 10MB block sustained READ/WRITE test. Here's the revealing results using four different drive interfaces:




(I pulled the IBM 120GXP results until I can retest with the same tweaks.)



If you run any speed test on a freshly formatted drive, you are only measuring the speed at the beginning or fastest portion of the drive. The speed loss can be quite dramatic as the disk fills up. If you have an application that requires a certain guaranteed minimum sustained transfer speed and you plan to fill up the drive, then the speed at the "end" of the drive is more critical to measure than the speed at the beginning.

Some drive manufacturers actually publish the speed variance between the beginning "zone" and the ending "zone." IBM, for example, claims 48MB/sec to 23MB/sec sustained data rate range in the PDF document with specifications of the 120gxp.

As you can see from the results, the percentage of speed loss varies depending on what drive you use and/or what interface it is running on (FireWire versus Ultra ATA-66 versus Ultra ATA-100 versus ATA-133).


ATA-66 vs ATA-100/133

In the first version of this page, I talked about the ATA-66 internal interface being much slower than ATA-100 (and ATA-133). I made two adjustments and retested.
1. I turned off Control Strip. I found out (according to PeekABoo) that it was using 50% of the CPU to do I don't know what. It was making the DUPLICATE test run slower (since Finder runs at a lower priority than Control Strip).
2. I formatted the drives using Apple's Drive Setup instead of Intech's HD Speed Tools. That seemed to give a boost to the ATA-66 times particularly.

However, if you look at the sustained WRITE speeds using 10MB blocks, the ATA-66 interface doesn't squeeze as much speed out of the drive as the ATA-100 and ATA-133. It's high time for Apple to start using at least ATA-100 inside their Power Macs! How about a little state of the art, please?

If you own a Power Mac and want the maximum throughput to your newest, fastest drives, then I recommend you purchase an ATA-100 or ATA-133 PCI controller card. But keep in mind, again, the speed at the "end" of the drive and don't get dazzled by the speed at the beginning.



I'm sad to report that Storage Review may be shutting down operation but while they still have reports posted, I suggest you look at the recent test of the WD1200JB.

Read Bare Feats' report on Ultra ATA and FireWire RAID setups on the Mac.



The test "mule" was the Apple Power Mac G4/800MP.

The ATA-100 PCI card used was Sonnet Tempo ATA-100 PCI adapter.

The ATA-133 PCI card used was The Acard AEC-6880M True Hardware RAID Ultra ATA-133.

The hard drive used was the Western Digital Caviar WD1200JB (120GB, 7200rpm, 8MB buffer)

The FireWire enclosure kit used was the Granite Digital "911" Case Kit.


QuickBench, a handy benchmarking tool from
Intech (the creators of HD Speed Tools), was used to measured sustained WRITE speed using 10MB blocks. This is useful for those of you choosing a drive for Video or Audio capture.

For the real world test, I used the pak0.pak3 file from Quake 3 which is 457MB in size. By duplicating this file on a drive, it forces it to read and write to itself simultaneously. It's also big enough that it should defeat the advantage of any large drive buffer. I calculate the megabytes/second transfer speed by the formula SIZE * 2 / TIME.



NewEgg.com has the best price on the IBM 120gxp and WD1200JB.

For the Sonnet Tempo ATA-100 PCI adapter, you can buy from Small Dog Electronics for $99.

The Acard AEC-6880M True Hardware RAID Ultra ATA-133 card is available from Other World Computing. Sonnet just announced taht they will be selling it under their label as the Tempo RAID133. An alert reader found the same card with the SIIG label on TheNerds.Net for $132. (Search on the catalog number: 989889) Same card and uses same firmware.

The Granite Digital "911" Case Kit can be purchased direct from Granite Digital for $159. It's funky looking and has two fans but it's the fastest FireWire case money can buy. If you want a slimmer case with no fan (quieter), I also like the Elite Oxford 911 case from Other World Computing going for $107.

See the STORAGE section of my HOT DEALS page for more good sources of the products tested on this page.



© 2002 Rob Art Morgan
"BARE facts on Macintosh speed FEATS"
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