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原创 Load/Unload Cycles in Mechanical Hard Disks

2013-5-19 22:27 1655 0 分类: 工程师职场

A long time ago, the IBM manufactured hard disks with their own brand name.

The two well-known series were "Deskstar" and "Travelstar", which are still being used by HGST (of Western Digital). Deskstar was 3.5-inch HDDs for desktops while Travelstar was 2.5-inches for notebooks.
 

ibm-front.jpg
Fig. An IBM's deskstar hard drive
(Image: http://www.xbitlabs.com)


I found that the arm (slider) and read/write head of my IBM hard drive would 'park' outside the disk area when it is powered on, where that of other brands seemed to be not moving out. After power on, the slider would move into the disk area.
 

bimghitachi hds721680pla380.jpg
Fig. The read/write head is outside the platter when disk is powered off
(Image: http://www.getprice.com.au)
 
untitled - 1.jpg
Fig. Slider (with read/write head) could park outside the platter area
(Image: http://www.hgst.com)


As time went by, more and more hard disk manufacturers use this mechanism in their drives. The read/write head would park outside when idle during the power is on. Then the Load/Unload cycle count, which means the times that the slider move into and out of the platters, would increase significantly in a short period of time.


ll.jpg

Fig. A large load/unload cycle count of a 'quite-new' hard drive
(Image: http://www.overclock.net)


Since a hard drive could fail when the read/write head is crashed with the platter and damage it, many people are concerned about this issue. I even tried to increase the idle time to park the head of my WD's hard drive using wdidle3.

The manufacturers claim that there are many benefits of using this mechanism, including reduced power consumption.
 

untitled - 2.jpg
Fig. Said benefits of parking the head
(Image: http://www.hgst.com)
 
As the manufactures are putting a huge amount on researches, as consumers we just can believe that this technology is meaningful.... 彷徨
However, do keep it mind that we should check the SMART status regularly, avoid any shock to the disk drives and keep a copy if necessary... since the data inside is usually more valuable than the drive 纵容

Reference: A document from HGST about the Load/Unload technology:
http://www.hgst.com/tech/techlib.nsf/techdocs/9076679E3EE4003E86256FAB005825FB/$file/LoadUnload_white_paper_FINAL.pdf
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