Hitachi Z7K320

I had to make a snap decision today on whether to buy a new hard drive for my x220t. The x220t only takes 7mm drives, which are less common than the typical 9.5mm drive for most notebooks. So seeing a 7200rpm drive on sale really caught my eye.

Drive performance was my primary concern, capacity was secondary. Sadly, few people actually published benchmarks for this drive. Mostly I just found marketing hyperbole and speculation.

The folks at Red Hill were kind enough to share a formula that they found was consistently able to predict a hard drive's performance: (2 log(data transfer rate) / sqr(seek + latency)). The higher the number, the faster the drive should perform.

Since my x220t is at home, I had to guess what hard drive it actually uses. So I chose the Seagate Momentus Thin based on vague recollections and what specifications I knew (250GB, 5400rpm, 7mm thickness). (Update: yes, exactly right, the ST9250301AS.) Here are the relevant numbers:

DTR 300 MB/s
random read seek 14ms
average latency 5.6ms
calculated result 1.119

This is the drive that was on sale at newegg.ca:

Hitachi Z7K320:
DTR 300 MB/s
average read seek 13ms
average latency 4.2ms
calculated result 1.195

So a slight performance improvement, according to the forumla.

It's possible I am making an apples-to-oranges comparison because I had to use "random read seek" versus "average read seek". Also, I've seen conflicting numbers for the Momentus Thin. If its seek time is actually 11ms according to this, then it's faster than the Hitachi, which defies expectations.

After a little more searching, I found a comparison between the z7k320 against the z7k500:

*** TRAVELSTAR 7K500 ***
-----------------------------------------------------------------------
CrystalDiskMark 3.0 (C) 2007-2010 hiyohiyo
Crystal Dew World : http://crystalmark.info/ -----------------------------------------------------------------------
* MB/s = 1,000,000 byte/s [SATA/300 = 300,000,000 byte/s]

Sequential Read : 111.361 MB/s
Sequential Write : 112.255 MB/s
Random Read 512KB : 39.582 MB/s
Random Write 512KB : 49.046 MB/s
Random Read 4KB (QD=1) : 0.516 MB/s [ 126.0 IOPS]
Random Write 4KB (QD=1) : 0.772 MB/s [ 188.6 IOPS]
Random Read 4KB (QD=32) : 0.972 MB/s [ 237.4 IOPS]
Random Write 4KB (QD=32) : 0.787 MB/s [ 192.0 IOPS]

Test : 1000 MB [D: 0.0% (0.1/232.9 GB)] (x5)
Date : 2010/12/14 16:13:58
OS : Windows 7 Home Premium Edition [6.1 Build 7600] (x86)


*** TRAVELSTAR Z7K320 ***
-----------------------------------------------------------------------
CrystalDiskMark 3.0 (C) 2007-2010 hiyohiyo
Crystal Dew World : http://crystalmark.info/ -----------------------------------------------------------------------
* MB/s = 1,000,000 byte/s [SATA/300 = 300,000,000 byte/s]

Sequential Read : 107.458 MB/s
Sequential Write : 106.552 MB/s
Random Read 512KB : 43.852 MB/s
Random Write 512KB : 47.439 MB/s
Random Read 4KB (QD=1) : 0.578 MB/s [ 141.2 IOPS]
Random Write 4KB (QD=1) : 1.085 MB/s [ 264.9 IOPS]
Random Read 4KB (QD=32) : 1.037 MB/s [ 253.3 IOPS]
Random Write 4KB (QD=32) : 1.091 MB/s [ 266.3 IOPS]

Test : 1000 MB [D: 0.0% (0.1/298.1 GB)] (x5)
Date : 2010/12/16 17:01:09
OS : Windows 7 Home Premium Edition [6.1 Build 7600] (x86)

According to the xbitlabs roundup, the 7K500 was the fastest among a group of 500-750GB drives. Yet the z7k320 had higher random read and write numbers than the 500, according to the Italian benchmark. So it does look like the z7k320 is a real performer, and the answer is "GO! BUY! NOW!"