SSW Self Head Erase check for ID Head Erase (20-Jan-2010)
Before start to write servo track pattern by Servo Track Writer ( STW ), STW confirms whether STW pattern has been already written on media disk or not. If STW pattern is found, STW starts to do head erase for required area, if not, STW does not do head erase.
SSW Self Head Erase check for ID Head Erase
STW(Servo Track Write) requires to do head erase STW pattern before writing STW pattern in case STW pattern is already written on Hard Disk Drive(HDD),
because magnetic eraser can not erase STW pattern on media disk completely.
On the other hands, newly assembled HDD, on which media STW pattern is not written, does not need to do head erase at STW.
To do head erase, head erase process time is required, therefore, from production point of view, the ratio of doing head erase units should be optimized.
In order to distinguish which units should be erase or not, there is 2 ways.
A. record the information of HDD history, then, STW will get the information which units should be done head erase by HDD's serial number ( identify information ).
B STW sees the media to find whether STW pattern has been already written, then if
STW patten is found, STW does do head erase.
In case the production volume is huge, "A" will have a problem in getting all the information on line because the tracking transaction will be increased drastically.
"B" will be the realistic way to optimize the number of head erase units.
To find STW patten is already written on media, STW has to check not only the area STW normally use but also the area servo information is written.
Disclosed by Hitachi Corporation
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