In just a week of use, the newer drive is exhibiting a large and growing number of Load Cycles. After a little research, I found that the WD10EADS drive comes in a number of flavors. The first configuration had 4 platters (each approx 250 GB). A second variant had 3 platters. The latest vintage, which is the kind I just bought, has a pair of 500 GB platters. I am seeing vastly different behavior from the two WD10EADS units, as reported by the Duo's SMART reports.
Drive 2: WDC WD10EADS-00L5B1. This is a 3-platter drive, installed in my Duo last month.
- power-on hours = 1012
- Load Cycle Count = 670
- Power Cycle Count = 78
Drive 1: WDC WD10EADS-00M2B0. this is the newer 2-platter drive, installed last week.
- power-on hours = 74
- Load Cycle Count = 3477
- Power Cycle Count = 10
The LCC value on Drive 1 increases by 2 or 3 every minute or so.
I have my Duo configured to spin-down the drives after 10 minutes. Even so, the LCC continues to climb, even when the drives should both be spun down.
I've done some web research and found extensive coverage of this issue at QNAP, Synology and Quiet PC Review forums. The root cause appears to be that the WD power-saving 'green' design parks the heads after 8 seconds of inactivity, while the Linux OS tickles the drive every 20 seconds or so, thereby unparking the heads. The Green series of drives are rated by WD for 300K load cycles during the drive's lifetime. Thus, there is some concern that the constant park/unpark operations will wear out the drive prematurely.
One customer received back from Western Digital a troubling statement:
...The unit is not recommended for NAS or RAID use, due to its end-user design. But, under normal use, rather than strenuous or highly demanding tasks, there should be not much issue with the unit.
Western Digital Service and Support
I can't explain why my two WD10EADS drives are behaving differently. I can think of three possibilities:
- - the two different models have different firmware, and they park/unpark the heads using different algorithms. (note that both my drives have the same 01.00A01 firmware).
- the two models are both parking/unparking the same, but are reporting differently through SMART. In other words, my Drive 2 also has large LCC count, but I just don't know it. It's been suggested by some experts that WD deliberately masked the actual operational statistics reported by some of their other drives in order to quell consumer concerns.
- my Drive 1 is operating as the Linux boot drive, and is being frequently accessed by the kernel as the kernel goes about its routine tasks. But Drive 2 is merely a RAIDed data disk that does not get repetitive accesses.
Detailed discussion and debate on this topic can be found here:
Based on my observed SMART reports, I feel some caution is warranted re the use of WD10EADS drives in RAIDed ReadyNAS systems. Be aware that all such drives are not created equal: you need to know the full part number to know if you have a 4-platter, 3-platter, or 2-platter unit.