Dynamic write cache size adjustment in raid controller with capacitor backup energy source

• US 7,451,348 B2
• Filed: 06/02/2006
• Issued: 11/11/2008
• Est. Priority Date: 08/04/2005
• Status: Expired due to Fees

• Current Assignee: Dot Hill Systems Corporation (Seagate Technology Holdings Plc)
• Original Assignee: Dot Hill Systems Corporation (Seagate Technology Holdings Plc)
• Inventors: Pecone, Victor Key, Wang, Yuanru Frank
• Primary Examiner(s): Maskulinski; Michael C
• Application Number:
  US11/422,003
• Publication Number:
  US 20070033433A1
• Time in Patent Office: 893 Days
• Field of Search: None
• US Class Current: 714/14
• CPC Class Codes: G06F 1/305 in the event of power-supply fluctuations

Abstract

A high data availability write-caching storage controller has a volatile memory with a write cache for caching write cache data, a non-volatile memory, a capacitor pack for supplying power for backing up the write cache to the non-volatile memory in response to a loss of main power, and a CPU that determines whether reducing an operating voltage of the capacitor pack to a new value would cause the capacitor pack to be storing less energy than required for backing up the current size write cache to the non-volatile memory. If so, the CPU reduces the size of the write cache prior to reducing the operating voltage. The CPU estimates the capacity of the capacitor pack to store the required energy based on a history of operational temperature and voltage readings of the capacitor pack, such as on an accumulated normalized running time and warranted lifetime of the capacitor pack.

Claims

1. A method for improving the data availability of a write-caching storage controller having a capacitor pack used to supply power for backing up a volatile write cache to a non-volatile memory in response to a loss of main power, the method comprising:

determining whether reducing an operating voltage of the capacitor pack to a new value would cause the capacitor pack to be storing less energy than required for backing up the volatile write cache to the non-volatile memory; and

reducing a size of the volatile write cache, prior to said reducing said operating voltage, if said reducing said operating voltage to said new value would cause the capacitor pack to be storing less energy than required for backing up the volatile write cache to the non-volatile memory.

2. The method as recited in claim 1, further comprising:

estimating a capacity of the capacitor pack to store said energy required for backing up the volatile write cache to said non-volatile memory based on a history of temperature and said operating voltage readings of the capacitor pack during operation of the storage controller;

wherein said determining is based on said estimating said capacitance.

3. The method as recited in claim 2, further comprising:

displaying to a user an indication of said capacity.

4. The method as recited in claim 3, wherein said displaying to a user an indication of said capacity comprises displaying said capacity as a percentage of an original capacity of the capacitor pack.

5. The method as recited in claim 1, further comprising:

detecting a need to reduce said operating voltage of the capacitor pack to said new value;

wherein said determining is performed in response to said detecting said need.

6. The method as recited in claim 5, further comprising:

calculating an accumulated normalized running time of the capacitor pack;

wherein said detecting said need to reduce said operating voltage of the capacitor pack to said new value comprises determining that said accumulated normalized running time is greater than an accumulated calendar running time of the capacitor pack.

7. The method as recited in claim 6, wherein said calculating said accumulated normalized running time comprises:

(1) initializing said accumulated normalized running time;

(2) sensing said temperature and said operating voltage of the capacitor pack during an interval of time over which the capacitor pack is operated, after said initializing;

(3) determining a lifetime over which the capacitor pack would have a capacity to store at least a predetermined amount of energy if operated at said temperature and said operating voltage during said lifetime;

(4) normalizing said interval of time by a ratio of said warranted lifetime relative to said lifetime;

(5) adding said normalized interval of time to said accumulated normalized running time; and

(6) repeating steps (2) through (5) during operation of the storage controller.

8. The method as recited in claim 7, further comprising:

(7) initializing said accumulated calendar running time of the capacitor pack, prior to said step (2); and

(8) adding said interval of time to said accumulated calendar running time;

wherein said step (6) comprises repeating said steps (2) through (5) and (8) during operation of the storage controller.

9. The method as recited in claim 6, further comprising:

determining that said accumulated normalized running time of the capacitor pack is greater than said accumulated calendar running time, after said reducing said operating voltage of the capacitor pack to said new value; and

increasing said operating voltage of the capacitor pack, in order to increase an amount of energy stored in the capacitor pack.

10. The method as recited in claim 1, further comprising:

calculating said reduced size, prior to said reducing, based on a capacity of the capacitor pack to store energy based on a history of temperature and said operating voltage readings of the capacitor pack during operation of the storage controller.

11. A high data availability write-caching storage controller, comprising:

a volatile memory, comprising a write cache for caching write cache data;

a non-volatile memory, coupled to said volatile memory;

a capacitor pack, coupled to said volatile and non-volatile memory, for supplying power for backing up said write cache to said non-volatile memory in response to a loss of main power; and

a CPU, coupled to said volatile and non-volatile memory, for dynamically determining a size of said write cache, configured to;

determine whether reducing an operating voltage of the capacitor pack to a new value would cause the capacitor pack to be storing less energy than required for backing up said write cache having a current said size to said non-volatile memory; and

reduce said size of the volatile write cache, prior to reducing said operating voltage, if reducing said operating voltage to said new value would cause the capacitor pack to be storing less energy than required for backing up the write cache having said current said size to the non-volatile memory.

12. The controller as recited in claim 11, said CPU is further configured to:

estimate a capacity of the capacitor pack to store said energy required for backing up the volatile write cache to said non-volatile memory based on a history of temperature and said operating voltage readings of the capacitor pack during operation of the storage controller;

wherein said CPU determines whether to reduce said size of said write cache based on said estimated capacity.

13. The controller as recited in claim 12, said CPU is further configured to:

display to a user an indication of said capacity.

14. The controller as recited in claim 13, wherein said CPU displays to a user an indication of said capacity by displaying said capacity as a percentage of an original capacity of the capacitor pack.

15. The controller as recited in claim 11, said CPU is further configured to:

detect a need to reduce said operating voltage of the capacitor pack to said new value;

wherein said CPU determines whether to reduce said size of said write cache in response to said detecting said need.

16. The controller as recited in claim 15, further comprising:

calculating an accumulated normalized running time of the capacitor pack;

wherein said detecting said need to reduce said operating voltage of the capacitor pack to said new value comprises determining that said accumulated normalized running time is greater than an accumulated calendar running time of the capacitor pack.

17. The controller as recited in claim 16, wherein said CPU calculates said accumulated normalized running time by:

(1) initializing said accumulated normalized running time;

(2) sensing said temperature and said operating voltage of the capacitor pack during an interval of time over which the capacitor pack is operated, after said initializing;

(3) determining a lifetime over which the capacitor pack would have a capacity to store at least a predetermined amount of energy if operated at said temperature and said operating voltage during said lifetime;

(4) normalizing said interval of time by a ratio of said warranted lifetime relative to said lifetime;

(5) adding said normalized interval of time to said accumulated normalized running time; and

(6) repeating steps (2) through (5) during operation of the storage controller.

18. The controller as recited in claim 17, wherein said CPU is further configured to:

(7) initialize said accumulated calendar running time of the capacitor pack, prior to said step (2); and

(8) add said interval of time to said accumulated calendar running time;

wherein said step (6) comprises repeating said steps (2) through (5) and (8) during operation of the storage controller.

19. The controller as recited in claim 16, wherein said CPU is further configured to:

determine that said accumulated normalized running time of the capacitor pack is greater than said accumulated calendar running time, after reducing said operating voltage of the capacitor pack to said new value; and

increase said operating voltage of the capacitor pack, in order to increase an amount of energy stored in the capacitor pack.

20. The controller as recited in claim 11, wherein said CPU is further configured to:

calculate said reduced size, prior to reducing said size of said write cache, based on a capacity of the capacitor pack to store energy based on a history of temperature and said operating voltage readings of the capacitor pack during operation of the storage controller.

21. A method for improving the data availability of a write-caching storage controller having a capacitor pack used to supply power for backing up a volatile write cache to a non-volatile memory in response to a loss of main power, the method comprising:

determining a size of the volatile write cache for which the capacitor pack would have a capacity to store enough energy to backup said size volatile write cache to the non-volatile memory if an operating voltage of the capacitor pack was reduced to a new value; and

reducing the volatile write cache to said size, prior to reducing said operating voltage to said new value, if said size is less than a current size of the write cache.

22. The method as recited in claim 21, further comprising:

estimating said capacity of the capacitor pack based on a history of temperature and said operating voltage readings of the capacitor pack during operation of the storage controller;

wherein said determining said size of the write cache is based on said estimating said capacity.

23. The method as recited in claim 21, further comprising:

detecting a need to reduce said operating voltage of the capacitor pack to said new value;

wherein said determining said size of the write cache is performed in response to said detecting said need.

24. The method as recited in claim 23, further comprising:

calculating an accumulated normalized running time of the capacitor pack;

wherein said detecting said need to reduce said operating voltage of the capacitor pack to said new value comprises determining that said accumulated normalized running time is greater than an accumulated calendar running time of the capacitor pack.

25. The method as recited in claim 24, wherein said calculating said accumulated normalized running time comprises:

(1) initializing said accumulated normalized running time;

(2) sensing said temperature and said operating voltage of the capacitor pack during an interval of time over which the capacitor pack is operated, after said initializing;

(3) determining a lifetime over which the capacitor pack would have a capacity to store at least a predetermined amount of energy if operated at said temperature and said operating voltage during said lifetime;

(4) normalizing said interval of time by a ratio of said warranted lifetime relative to said lifetime;

(5) adding said normalized interval of time to said accumulated normalized running time; and

(6) repeating steps (2) through (5) during operation of the storage controller.

26. The method as recited in claim 25, further comprising:

(7) initializing said accumulated calendar running time of the capacitor pack, prior to said step (2); and

(8) adding said interval of time to said accumulated calendar running time;

wherein said step (6) comprises repeating said steps (2) through (5) and (8) during operation of the storage controller.

27. The method as recited in claim 24, further comprising:

determining that said accumulated normalized running time of the capacitor pack is greater than said accumulated calendar running time, after reducing said operating voltage of the capacitor pack to said new value; and

increasing said operating voltage of the capacitor pack, in order to increase an amount of energy stored in the capacitor pack.

28. A high data availability write-caching storage controller, comprising:

a volatile memory, comprising a write cache for caching write cache data;

a non-volatile memory, coupled to said volatile memory;

a capacitor pack, coupled to said volatile and non-volatile memory, for supplying power for backing up said write cache to said non-volatile memory in response to a loss of main power; and

a CPU, coupled to said volatile and non-volatile memory, configured to;

determine a size of said volatile write cache for which said capacitor pack would have a capacity to store enough energy to backup said size volatile write cache to said non-volatile memory if an operating voltage of said capacitor pack was reduced to a new value; and

reduce said volatile write cache to said size, prior to reducing said operating voltage to said new value, if said size is less than a current size of said write cache.

29. The controller as recited in claim 28, wherein said CPU is further configured to:

estimate said capacity of said capacitor pack based on a history of temperature and said operating voltage readings of said capacitor pack during operation of the storage controller;

wherein said CPU determines said size of said write cache based on said estimated capacity.

30. The controller as recited in claim 28, wherein said CPU is further configured to:

detect a need to reduce said operating voltage of said capacitor pack to said new value;

wherein said CPU determines said size of said write cache in response to detecting said need.

31. The controller as recited in claim 30, wherein said CPU is further configured to:

calculate an accumulated normalized running time of said capacitor pack;

wherein said CPU detects said need to reduce said operating voltage of said capacitor pack to said new value by determining that said accumulated normalized running time is greater than an accumulated calendar running time of said capacitor pack.

32. The controller as recited in claim 31, wherein said CPU calculates said accumulated normalized running time by:

(1) initializing said accumulated normalized running time;

(2) sensing said temperature and said operating voltage of said capacitor pack during an interval of time over which said capacitor pack is operated, after said initializing;

(3) determining a lifetime over which said capacitor pack would have a capacity to store at least a predetermined amount of energy if operated at said temperature and said operating voltage during said lifetime;

(4) normalizing said interval of time by a ratio of said warranted lifetime relative to said lifetime;

(5) adding said normalized interval of time to said accumulated normalized running time; and

(6) repeating steps (2) through (5) during operation of the storage controller.

33. The controller as recited in claim 32, wherein said CPU is further configured to:

(7) initialize said accumulated calendar running time of said capacitor pack, prior to said step (2); and

(8) add said interval of time to said accumulated calendar running time;

wherein said step (6) comprises repeating said steps (2) through (5) and (8) during operation of the storage controller.

34. The controller as recited in claim 31, wherein said CPU is further configured to:

determine that said accumulated normalized running time of said capacitor pack is greater than said accumulated calendar running time, after reducing said operating voltage of said capacitor pack to said new value; and

increase said operating voltage of said capacitor pack, in order to increase an amount of energy stored in said capacitor pack.