I have some questions about HDDS, please explain.

[Matiw]

- When there is mechanical failure with HDD heads (broken head, stiction etc), what are the chances that it is multi-head failure ?

- Whan files are saved, are they multiplexed among the platters ? Or are platters used consecutively one after another (one is filled before the other is used) ?

Thanks

[pcimage]

- When there is mechanical failure with HDD heads (broken head, stiction etc), what are the chances that it is multi-head failure ?

- Whan files are saved, are they multiplexed among the platters ? Or are platters used consecutively one after another (one is filled before the other is used) ?

Thanks

More often than not, multiple heads fail.

Data is "multiplexed" across platters in "zones", some drives however have large zones (e.g. Samsung) with many Gb being recorded in one lump on one surface.

[fzabkar]

IMO the term "zones" is inappropriate in this case because it can be confused with the zones in Zone Bit Recording (ZBR). Instead I would suggest that they be described as "serpentine segments".

The following article should help the OP understand the difference:
http://hddscan.com/doc/HDD_Tracks_and_Zones.html

The following thread illustrates this serpentine behaviour for those drives with variable bits per inch.

How to determine number of heads using HD Tune:
http://malthus.zapto.org/viewtopic.php?f=59&t=650

[pcimage]

IMO the term "zones" is inappropriate in this case because it can be confused with the zones in Zone Bit Recording (ZBR). Instead I would suggest that they be described as "serpentine segments".

The following article should help the OP understand the difference:
http://hddscan.com/doc/HDD_Tracks_and_Zones.html

The following thread illustrates this serpentine behaviour for those drives with variable bits per inch.

How to determine number of heads using HD Tune:
http://malthus.zapto.org/viewtopic.php?f=59&t=650

"Zone Bit Recording".... "Serpentine Segments" ????

How is that easier for the OP to understand than my simplified explanation??

Although maybe not 100% technically exact, I believe the OP understood what I meant. Which is exactly what I was attempting to do, in simple terms, not show off.

P.S. Yes, I DO know and understand what those terms mean before you flame me yet again.

[fzabkar]

Man, no need to get your knickers in a twist.

The term "serpentine" was used in the "Tracks and Zones" article written by Doomer, so if you have an issue with it, then please take it up with him. The article also explains the traversal of the platters pictorially, so, yes, it is a lot better than your "simplified" explanation.

Moreover, the HD Tune graphs illustrate the behaviour in a practical sense, for several different HDD brands. Therefore, I think I have covered most of the bases ... without trying to show off.

[Matiw]

Thank pcimage/ fzabkar/ Spildit, I do now have a better understanding about the issue.

fzabkarºs pointer was specially helpful.

I have a follow up question though. Does the use of alternate heads (one after another to reduce Head-movement and for Load-balancing) begines anew with every write operation, or does it just continue from where it left in the last write operation ?

Thasnks for any info.

[Matiw]

I am asking these questions in order to analyse the effectivness of head-Map editing in RAM (without further steps) for data recovery purpose. Any feedback to this end is highly appreciated.

Thanks.