Comparison of HDD/SDD on Dell Latitude D620 running RHEL-6

Recently I got into my hands Kingston SSDnow V+ series 128GB SNVP325-S2/128GB and Dell Latitude D620 laptop that was equipped with Hitachi HTS721010G9SA00 HDD. So I prepared simple power consumption related comparison.

I measured time and energy that was consumed for various tasks. All tasks were run three times and average values were counted. From the time and energy the average power consumption of the whole system was calculated. I measured HDD for various settings of accoustic management, R/W multiple sector transfer, and advanced power management level. On SSD most of these settings were not available and it only supported subset of advanced power management levels. I used Chroma 66202 ENERGY STAR/IEC 62301 compliant power meter (http://www.chromaate.com/product/detail.aspx?id=1593). Between measurements the I/O cache was flushed. During the measurement display dimming, screensaver and cron were disabled.

In the table 1 there are results for RHEL-6 Kickstart provision, cold boot, kernel sources unpack (3 times in a row with cache flush), mock targeted kernel rebuild and 1 hour active idle test. In the table the results for HDD and SSD are compared with help of colours - green colour stands for better results and red colour for worse results.

Table 1: Power consumption of HDD/SSD for various tasks.

Task		HDD			SSD
		t [s]	Pavg [W]	E [Wh]	t [s]	Pavg [W]	E [Wh]
Kickstart provision		854.00	41.20	9.774	754.00	39.83	8.342
Boot		50.00	38.34	0.533	40.00	37.38	0.415
Kernel 2.6.32 unpack (3 times)		76.39	39.00	0.828	65.83	38.31	0.701
Mock build kernel-2.6.32-79		8689.25	42.78	103.257	8083.51	41.21	92.534
Active idle for 1 hour	Advanced power management level: 128	3600.00	21.05	21.050	3600.00	19.32	19.320
	Advanced power management level: 255	3600.00	21.20	21.200	-	-	-
	Advanced power management level: 1	3600.00	20.94	20.940	3600.00	19.32	19.320

From the table 1 it is apparent that for all measured tasks the SSD was better. Not only all tasks were finished in less time but also less energy was consumed.

In the table 2 there are results for sequential read test. For this test the hdparm -t command was used. In this test the average read and peak read speeds in MB/s from the three runs were observed.

Table 2: Power consumption/performance of HDD/SSD during sequential read.

Task		HDD					SSD
		t [s]	Pavg [W]	E [Wh]	Average read [MB/s]	Peak read [MB/s]	t [s]	Pavg [W]	E [Wh]	Average read [MB/s]	Peak read [MB/s]
Sequential read (hdparm -t)	Acoustic management: 254 Advanced power management level: 128 R/W multiple sector transfer: 8	18.53	26.00	0.134	39.17	43.06	18.31	21.23	0.108	115.90	115.97
	Acoustic management: 254 Advanced power management level: 254 R/W multiple sector transfer: 16	18.34	25.39	0.129	48.23	48.26

From the table 2 it is apparent that the SSD was again better in all observed parameters.

In the table 3 there are results for random seek test. For this test the seeker utility was used. During this test the average seek time in ms was observed. Also the maximal acoustic noise level in dBA was measured during this test. The acoustic noise level numbers are only informal, because uncalibrated equipment was used. The measurement was done remotely in the office during night. The background noise level was measured to be about 30 dBA there.

Table 3: Power consumption/performance of HDD/SSD during random seeks.

Task		HDD					SSD
		t [s]	Pavg [W]	E [Wh]	Acoustic noise max [dBA]	Average seek [ms]	t [s]	Pavg [W]	E [Wh]	Acoustic noise max [dBA]	Average seek [ms]
Random seek	Acoustic management: 254 Advanced power management level: 128 R/W multiple sector transfer: 8	30.31	27.88	0.235	40	15.43	30.02	22.82	0.190	30	0.25
	Acoustic management: 254 Advanced power management level: 254 R/W multiple sector transfer: 16	30.33	28.05	0.236	40	15.82
	Acoustic management: 128 Advanced power management level: 128 R/W multiple sector transfer: 8	29.34	27.89	0.227	37	16.62

In the table 3 you can see that the SSD was again better in all observed parameters.

The SSD was better in all tests, but it is worth to note that it was quite a new SSD and really old laptop with old HDD. In case the up-to-date and higher class HDD would be available these results wouldn't be probably such single-valued. Also the empty SSD was used in the test thus the internal wear levelling algorithms were not probably in effect and was not able to negatively affect the results as it would do during long term real life usage.