Archived from groups: comp.sys.ibm.pc.hardware.storage (
More info?)
"Folkert Rienstra" <see_reply-to@myweb.nl> wrote in message
news:2ofkbbF9s51dU2@uni-berlin.de...
>
> "Joep" <j o e p @ d i y d a t a r e c o v e r y . n l> wrote in message
news:56976$41224459$3eddca68$30209@nf1.news-service-com...
> > "Folkert Rienstra" <see_reply-to@myweb.nl> wrote in message
news:2oai9cF8b2ehU1@uni-berlin.de...
> > >
> > > You also need a special program to get rid of sectors that
successfully
> > > read after retries but that don't trigger the sparing process.
> > >
> >
> > But 'normally' this would trigger the sparing process?
>
> You appear to have snipped the "this". Presumably you meant:
>
> > reading 'weak' sector successfully already triggers the reallocation
> > mechanism, at least from my observations
>
Yes, I did, sorry ...
> If the sector is read with retries after a specific ERP/DRP point is
reached.
>
> God knows what he meant with "at least from my observations" when
> that cannot possibly be 'observed'.
>
> > And under what condition wouldn't it?
>
> If the sector is read with retries but that specific ERP/DRP point is not
yet reached.
> There can be up to 50 steps in a recovery procedure.
>
> ERP = Error Recovery Procedure. DRP = Data Recovery Procedure
> The data recovery process is a set of measures outside of normal operation
> that is invoked to get the drive to read a sector when normal operation
fails.
>
> Here are a few terms as used in the DRP process of my IBM DFHS.
>
> Reread - Read with no parameters altered.
> Rewrite - Write with no parameters altered.
> Read Bias - 0 = Normal Bias Current in Read Head,
> + 1 = Increase Bias Current in Read Head by 1 unit,
> -1 = Reduce Bias Current in Read Head by 1 unit.
> TO - Track Offset movement of the Read Head slightly off center. The
percent
> indicates the fraction of a track width. The sign indicates the direction
of the
> movement with + being toward the inner diameter of the data surface.
> ECC Burst - Amount of ECC correction applied. Double Burst will correct a
> 41 bit error and under certain conditions can correct up to a 48 bit
error.
> These are errors per physical sector.
> DA - Double burst ECC correction on adjacent error bytes.
> DR - Double burst ECC correction on adjacent or random
> TB - Triple burst ECC correction on adjacent error bytes. This allows 9
bytes
> in error to be corrected.
> SAT - Surface Analysis Test ECC correction on adjacent error bytes. This
> allows certain 14 byte errors to be corrected when a thermal asperity is
involved.
> EQ - Equalizer Adjust, the Channel Hardware is set to a fixed mode with
the
> equalizer adjusted based on the amount shown.
> TA Mode - Set the channel to thermal asperity recovery mode regardless of
> whether a thermal asperity was detected or not.
> NSF - No Sector Found error.
> NO ID Mode - Data recovery using tangentially adjacent sector IDs to
deter-
> mine the physical location of the NSF ID. A physical operation is
performed to
> read or write the data.
> HSC - Head State Change, A short write is done in the non-customer data
area
> to change the residual head state characteristics.
> VCO Calibrate - Calibrates the Voltage Controlled Oscillator in the
Channel
> Hardware.
> A/D Calibrate - Calibrates the Anolog to Digital Convertor in the Channel
> Hardware.
> Scrub - Movement of the head in an attempt to recovery from an error
possibly
> caused by a Thermal Asperity. Scrub is done in a particular direction,
either
> toward the Inner Diameter(ID) or toward the Outer Diameter(OD). Asperity
> off the disk. Several disk revolutions are taken on each step which
employs this
> type of recovery.
> Read Gate Adjust Recovery - Adjust where Data Sync is read in an attempt
to
> avoid a Thermal Asperity in the Data Sync Field. The amount of adjust is
> fixed. The polarity of the adjust can be early or late.
>
>
Thanks Folkert!
--
Joep