Data storage device delaying seek operation to avoid thermal asperities
View Patent ↗A data storage device is disclosed comprising a head actuated over a disk comprising a plurality of tracks, wherein at least two of the tracks comprise a thermal asperity. Prior to seeking the head from a first track to a second track, for each of at least two of the thermal asperities a minimum seek delay and a maximum seek delay that will cause the head to miss the thermal asperity are computed, and an allowed seek delay range that will cause the head to miss the thermal asperity is computed. When the undelayed seek will cause the head to hit at least one thermal asperity, the seek is delayed by a seek delay determined based on the minimum seek delays, the maximum seek delays, and the allowed seek delay ranges.
1. A data storage device comprising:
a disk comprising a plurality of tracks, wherein at least two of the tracks comprise a thermal asperity;
a head actuated over the disk; and
control circuitry configured to seek the head from a first track to a second track by at least:
for each of at least two of the thermal asperities:
when an undelayed seek will cause the head to hit the thermal asperity, computing a minimum seek delay and a maximum seek delay that will cause the head to miss the thermal asperity; and
when the undelayed seek will cause the head to miss the thermal asperity, computing an allowed seek delay range that will cause the head to miss the thermal asperity; and
when the undelayed seek will cause the head to hit at least one of the thermal asperities, delaying the seek by a seek delay determined based on the minimum seek delays, the maximum seek delays, and the allowed seek delay ranges.
2. The data storage device as recited in claim 1 , wherein the seek delay comprises a minimum seek delay determined based on the minimum seek delays, the maximum seek delays, and the allowed seek delay ranges.
3. The data storage device as recited in claim 2 , wherein for one of the thermal asperities the control circuitry is further configured to compute the minimum seek delay and the maximum seek delay according to:
{
t
min
,
i
=
w
i
1
-
w
i
,
t
max
,
i
=
Rev
+
w
i
0
-
w
i
,
if
w
i
0
≤
w
i
1
t
min
,
i
=
Rev
+
w
i
1
-
w
i
,
t
max
,
i
=
Rev
+
w
i
0
-
w
i
,
if
w
i
0
>
w
i
1
,
w
i
>
w
i
0
t
min
,
i
=
w
i
1
-
w
i
,
t
max
,
i
=
w
i
0
-
w
i
,
if
w
i
0
>
w
i
1
,
w
i
<
w
i
1
i represents an index for the thermal asperity;
t min,i represents the minimum seek delay;
t max,i represents the maximum seek delay;
w i represents a servo wedge in the thermal asperity where the head will hit the thermal asperity during the undelayed seek;
w i0 and w i1 represent servo wedges that define a boundary of the thermal asperity; and
Rev represents a total number of servo wedges in the track comprising the thermal asperity.
4. The data storage device as recited in claim 3 , wherein for one of the thermal asperities the control circuitry is further configured to compute the allowed seek delay range according to:
t d ε[0, t minNot,i ]∪[t maxNot,i ,Rev−1] where
{
t
minNot
,
i
=
w
i
0
-
w
i
-
1
,
t
maxNot
,
i
=
w
i
1
-
w
i
+
1
,
if
w
i
0
≤
w
i
1
,
w
i
<
w
i
0
t
minNot
,
i
=
Rev
+
w
i
0
-
w
i
-
1
,
t
maxNot
,
i
=
Rev
+
w
i
1
-
w
i
+
1
,
if
w
i
0
≤
w
i
1
,
w
i
>
w
i
1
t
minNot
,
i
=
w
i
0
-
w
i
-
1
,
t
maxNot
,
i
=
w
i
1
-
w
i
+
1
,
if
w
i
0
>
w
i
1
where:
i represents an index for the thermal asperity; and
t d represents the allowed seek delay range.
5. The data storage device as recited in claim 3 , wherein the control circuitry is further configured to compute the seek delay by:
for all cases where the head will hit the thermal asperities computing an acceptable delay range according to:
t min = t min,i +1, t max = t max,i −1
if t min ≦t minNot,i for all cases where the head will miss the thermal asperities then setting the seek delay equal to t min , otherwise for each case where the head will miss the thermal asperities if t min >t minNot,i then t min =t maxNot,i .
6. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to:
store a plurality of access commands in a command queue; and
execute a rotational position optimization (RPO) algorithm to determine an execution order for the access commands based on the seek delay determined for at least two of the access commands.
7. A method of operating a data storage device, the method comprising:
seeking a head over a disk from a first track to a second track by at least:
for each of at least two of a plurality of thermal asperities on the disk:
when an undelayed seek will cause the head to hit the thermal asperity, computing a minimum seek delay and a maximum seek delay that will cause the head to miss the thermal asperity; and
when the undelayed seek will cause the head to miss the thermal asperity, computing an allowed seek delay range that will cause the head to miss the thermal asperity; and
when the undelayed seek will cause the head to hit at least one of the thermal asperities, delaying the seek by a seek delay determined based on the minimum seek delays, the maximum seek delays, and the allowed seek delay ranges.
8. The method as recited in claim 7 , wherein the seek delay comprises a minimum seek delay determined based on the minimum seek delays, the maximum seek delays, and the allowed seek delay ranges.
9. The method as recited in claim 8 , wherein for one of the thermal asperities the method further comprises computing the minimum seek delay and the maximum seek delay according to:
{
t
min
,
i
=
w
i
1
-
w
i
,
t
max
,
i
=
Rev
+
w
i
0
-
w
i
,
if
w
i
0
≤
w
i
1
t
min
,
i
=
Rev
+
w
i
1
-
w
i
,
t
max
,
i
=
Rev
+
w
i
0
-
w
i
,
if
w
i
0
>
w
i
1
,
w
i
>
w
i
0
t
min
,
i
=
w
i
1
-
w
i
,
t
max
,
i
=
w
i
0
-
w
i
,
if
w
i
0
>
w
i
1
,
w
i
<
w
i
1
where:
i represents an index for the thermal asperity;
t min,i represents the minimum seek delay;
t max,i represents the maximum seek delay;
w i represents a servo wedge in the thermal asperity where the head will hit the thermal asperity during the undelayed seek;
w i0 and w i1 represent servo wedges that define a boundary of the thermal asperity; and
Rev represents a total number of servo wedges in the track comprising the thermal asperity.
10. The method as recited in claim 9 , wherein for one of the thermal asperities the method further comprises computing the allowed seek delay range according to:
t d ε[0, t minNot,i ]∪[t maxNot,i ,Rev−1] where
{
t
minNot
,
i
=
w
i
0
-
w
i
-
1
,
t
maxNot
,
i
=
w
i
1
-
w
i
+
1
,
if
w
i
0
≤
w
i
1
,
w
i
<
w
i
0
t
minNot
,
i
=
Rev
+
w
i
0
-
w
i
-
1
,
t
maxNot
,
i
=
Rev
+
w
i
1
-
w
i
+
1
,
if
w
i
0
≤
w
i
1
,
w
i
>
w
i
1
t
minNot
,
i
=
w
i
0
-
w
i
-
1
,
t
maxNot
,
i
=
Rev
+
w
i
1
-
w
i
+
1
,
if
w
i
0
>
w
i
1
where:
i represents an index for the thermal asperity; and
t d represents the allowed seek delay range.
11. The method as recited in claim 9 , further comprising computing the seek delay by:
for all cases where the head will hit the thermal asperities computing an acceptable delay range according to:
t min = t min,i +1, t max = t max,i −1
if t min ≦t minNot,i for all cases where the head will miss the thermal asperities then setting the seek delay equal to t min , otherwise for each case where the head will miss the thermal asperities if t min >t minNot,i then t min =t maxNot,i .
12. The method as recited in claim 7 , further comprising:
storing a plurality of access commands in a command queue; and
executing a rotational position optimization (RPO) algorithm to determine an execution order for the access commands based on the seek delay determined for at least two of the access commands.