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Western Digital RE4-GP 2TB
The Western Digital RE4-GP is an enterprise-grade drive carrying Western Digital’s “Green Power” designation.
As we shall see, saving a few watts entails a performance hit that not all users will find appealing, making the RE4-GP perform more like a consumer-grade 2TB drive for sustained data transfer.
However, the RE4-GP does have a 64MB onboard cache, which is twice the 32MB cache found on 1GB hard drives, and most 2GB hard drives. This might aid its performance in some types of random access applications.
For details on the RE4-GP in general, see Background, below.
Test results PERMALINK
Test drives were supplied by OWC were tested with a Mac Pro Nehalem 2.66GHz 4-core on Mac OS X 10.6.1 Snow Leopard, using the internal SATA ports (drive bays). For the single-drive test, two units were tested and found to be identical in performance to a fraction of a percent.
DiskTester 'fill-volume' PERMALINK
The DiskTester fill-volume command fills any volume with 1000 equal-sized files, written in 32MB chunks for maximum performance. After the volume is filled, all files are read, to characterize read speed vs write speed (usually very close). This test takes 12-16 hours for a fast 2TB drive! The spikes at the very end should be ignored: a totally full hard drive is never advisable; the very end behaves strangely (bad block remapping, etc), this is true for all hard drives.
The fill-volume test represents the most important drive characteristic for a capacious hard drive: sustained transfer rate in real-world usage (file system access). It translates directly to performance using a Photoshop scratch volume, backing up, copying files, opening huge images, etc.
Hard drives slow down from the outer to inner tracks. Average write speed across the volume was 80.8MB/sec, read speed was 81.4MB/sec. This is solid performance, but not exciting.
Show below is a performance graph for the Western Digital RE4-GP compared to the Hitachi Deskstar 7K2000. The Hitachi 7K2000 is a much higher performance drive, offering about 20% higher performance, and more consistent performance as well.
For time reasons, I did not run DiskTester fill-volume on a 4-drive RAID-0 stripe, but I did run the run-area-test command, which yields an accurate approximation of across-the-drive performance (in a fraction of the time). As seen with many other drives, there is quirk where the end of the drive is as fast as the beginning (this is also seen with fill-volume, above).
Results in a 4-drive RAID-0 stripe are adequate, but not exciting. This is a bit below 2008 performance for fast 1TB drives, so it’s disappointing in a 2TB drive in 2009.
disktester run-area-test -i 3 -t 4G -c 32M re4gpX4 ... --- Averages for "re4gpX4" (4GB/32MB, 3 iterations) ---
Area (7.27TB) Write MB/sec Read MB/sec
0% 402 403
10% 385 385
20% 374 376
30% 359 363
40% 323 326
50% 324 328
60% 305 304
70% 286 285
80% 264 262
90% 236 234
100% 408 409
Average write speed across the volume: 333MB/sec
Average read speed across the volume: 334MB/sec
Formatted on a Mac, the resulting volume offers 1.82TB of storage (TB = 1024^3), which Mac OS X 10.6 Snow Leopard now displays as 2TB (1000^3). The actual amount of storage hasn't changed, only a decades-long definition terabyte (TB).
Before you get too excited about that amount of storage, make sure you have a robust backup strategy; if you have even 1TB of data, what would losing it all mean? How long to backup and restore it? It takes about 7 hours just to read that much data on the RE4-GP, let alone write it somewhere else (a backup drive).
Spindle speed and cache
The RE4-GP spins at an unspecified “IntelliPower” spindle speed. This clearly reduces its performance in terms of sustained transfer rate.
The RE4-GP is rated for 3.7 watts at idle, and 6.8 watts in use. By comparison, the Hitachi 7K2000 consumes about 7.5 watts at idle and 11.1 watts in use— a fair amount more for the drive itself, but of not much signifiance in a Mac Pro system as a whole.
The RE4-GP comes at a huge price premium over the 7K2000, so the fair comparison is to the Hitachi A7K2000, which takes only 5.1 watts at idle, narrowing the gap considerably. And the A7K2000 is 20-25% faster than thge RE4-GP.
If a drive takes 20% longer to complete a task, there is extra power used because the task takes longer. For real power savings, sleep the computer and *poof*, a Mac Pro suddenly is taking 160-200 watts less power, eclipsing drive savings.
The Western Digital RE4-GP is rated for 24X7 use (always on), in keeping with its “enterprise” designation.
The Western Digital RE4-GP is a solid performer, but hardly exciting from a performance standpoint. For high-density storage (enclosures with 4/6/8 drives), the lower power demands of the RE4-GP might well be a great answer. But Mac pro users are looking at a modest difference in power usage of ~watts per drive, or ~12 watts for four drives, hardly a major consideration.
Anyone looking for a fast system drive or a drive for the fastest possible Photoshop scratch volume (especially in a RAID) should be looking at full-speed 7200rpm drives, like the Hitachi Deskstar 2TB 7K2000. At the time this was written, the RE4-GP was also priced about 55% higher, so that decides it for most users. That said, the RE4-GP is classified as an enterprise-grade drive, and thus has a 5 year warranty and in theory could be more reliable.
Test drives supplied by OWC
The four drives used for testing were supplied by our site sponsor, Other World Computing. OWC is a great vendor to work with, so please give them your business. The 90-day drive replacement guarantee is a big plus, too, because especially with RAID, waiting weeks for the manufacturer is not an option.
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