jono-ats wrote:
You should ask Ace Lab this question. I have my own theories.
Suffice it to say that sometimes heads will pass the heads test, but you still cannot read customer LBAs. If a head passes the test but doesn't function in Data Extractor, then it is bad.
Hi jono-ats,
I don't say that head-test algorithm of ACE lab is absolute or perfect, it just helps
me to decide the head-swap as a first or last action in my data recovery process.
As to your example, I think you didn't choose a good example in this case. Head test
routine tests heads based on their physical parameters, while accessing usre LBAs in
data extractor involves logical parameters and translator tables too. Failing to access user
LBAs doesn't mean a faulty head necessarily. Please correct me if I am wrong.
You are correct. My statement was over-inclusive and thus faulty. However, in cases such as WD5000KS, replacing a head that fails in DE often resolves the problem. Therefore DE is one way to diagnose such bad heads.