Seagate Barracuda 7200.8: 400GBs with NCQ

Hard Drive Buffer: Does Size Really Matter?

The answer to the title of this section is simply, "YES!" A larger buffer will definitely prove to be a performance booster no matter what type of application we use most. We mentioned how NCQ helps organize the list of requested data into a logical order relative to their location on the hard disk, and also how the rotational speed of the spindle increases the speed at which data can be read and written by the hard drives' heads. Yet we also mentioned that the drive's on board cache can be the deciding factor on how much better it performs compared to other drives.

Why is the buffer so important?

Data flow to and from the system bus is a two-part process on the hard disk side. We are all familiar with solid state memory and how it is much faster than hard disk drives because solid state storage devices do not use moving parts, but instead store information on ICUs. This reduces transfer times because the solid state media does not have to search for data across a platter, in turn eliminating service times, seek times, etc. A hard drive's buffer and system bus act in a similar way through the interface. The buffer is the ICU that holds data until it is needed. The only difference is that the buffer of a hard disk drive is volatile, as it requires power to retain the data by which it is occupied, and solid state media devices are not and they can hold data without the need for a power source.

On the other side of the buffer, we have a data flow path from the media to the buffer and vice-versa. This flow of data is much slower than that between the buffer and the interface because of the mechanical characteristics of hard disk media. Since the read heads need to physically move to read and write data, the entire process is almost 33% slower on a SATA drive capable of 150MB/sec transfer rates. Without a buffer, the flow of data would be much slower than what we find on drives today and the hard disk would be an even tighter bottleneck than it currently is.

In our look at the SATA vs. IDE interfaces earlier, we tested two drives that are physically identical in every way except the interface. This is probably the best way possible to show the difference in performance, which is why we have chosen a 2MB PATA version of the Samsung SpinPoint to compare to the 8MB SP1614N PATA unit. Take a look at the performance advantage of an 8MB buffer over the SP1604's 2MB buffer.

2MB vs 8MB Drive Buffer
	SP1614N (8MB)	SP1604N (2MB)	8MB Performance Advantage
SYSMark 2004 - Internet Content Creation Performance
Overall	201	197	2.03%
3D Content Creation	181	179	1.12%
2D Content Creation	253	250	1.2%
Web Publication	177	171	3.51%
SYSMark 2004 - Office Productivity - Communication Performance
Overall	173	157	10.19%
Communication	199	153	30.01%
SYSMark 2004 - Overall System Performance
Overall Performance	186	176	5.68%
Internet Content Creation	201	197	2.03%
Office Productivity	173	157	10.19%
Winstone 2004 - Overall System Performance
Business	24	23.9	0.42%
Multimedia Content Creation	32.2	31.7	1.58%
Multitasking	2.79	2.72	2.58%
Pure Hard Disk Performance - IPEAK, Winstone 2004
Business	544	459	18.52%
Multimedia Content Creation	357	287	24.39%
Real World Performance - File System Tasks (seconds)
File Zip (1 300MB File)	60.321	61.519	1.99%
File Zip (300 1MB Files)	61.094	63.210	3.46%
File UnZip (1 300MB File)	13.928	14.048	0.86%
File UnZip (300 1MB Files)	14.260	14.366	0.74%
Copy Folder (1 300MB File)	5.271	7.853	48.99%
Copy Folder (300 1MB Files)	6.400	9.909	54.83%
Real World Performance - Application Load Times (seconds)
Photoshop CS	7.311	7.596	3.9%
Office 2003 - Word	2.040	2.466	20.88%
Office 2003 - Excel	2.189	2.437	11.33%
Office 2003 - Access	2.449	2.855	16.58%
Office 2003 - PowerPoint	2.090	2.817	34.78%
Real World Performance - Game Level Loading Times (seconds)
Half-Life 2 (d1_canals_01)	19.033	23.533	23.64%
Doom 3 (caverns1)	42.567	45.8	7.6%
C&C: Generals (GLA C3S1)*	33.967	34.7	2.16%
Service Time
IPEAK Average Read Service Time	13.53	14.18	4.8%
WinBench 99 - Transfer Rate Test
Beginning	60500	61100	-0.99%
End	36900	37600	-1.9%

The 8MB model took the win in most of the tests, and in some cases with about a 50% performance increase over the 2MB unit. There is obviously a performance advantage when increasing the drive cache from 2MB to 8MB. A larger cache means more efficient retrieval and organization of data before the hard disk drive sends it off to be processed. More is definitely better.