Apparatus to manage efficient data migration between tiers
A data storage system having a slow tier and a fast tier maintains hot data on the fast tier by migrating data from the slow tier to reserve space on the fast tier as data becomes hot over time. The system maintains a reserve space table and performs a mass migration of data from the fast tier to the slow tier. Data migration is frequently unidirectional with data migrating from the slow to the fast tier, reducing overhead during normal operation.
1. A data storage apparatus comprising:
a processor;
a first data storage device connected to the processor, configured to store a reserve space table of unmapped data blocks; and
a second data storage device connected to the processor,
wherein:
the first data storage device has a relatively faster access time than the second data storage device;
the reserve space table is configured to identify discrete portions of the first data storage device and discrete portions of the second data storage device; and
the processor is configured to:
transfer data from a discrete portion of the second data storage device to a discrete portion of the first data storage device identified in the reserve space table;
after transferring data from the discrete portion, add a location of the discrete portion of the second data storage device to the reserve space table and remove a location of the discrete portion of the first data storage device from the reserve space table;
transfer data from a plurality of discrete portions of the first data storage device to a plurality of discrete portions of the second data storage device;
after transferring data from the plurality of discrete portions add a plurality of locations, each associated with one of the plurality of discrete portions of the first data storage device to the reserve space table and remove a plurality of locations, each associated with one of the plurality of discrete portions of the second data storage device from the reserve space table.
2. The data storage apparatus of claim 1 , wherein the processor is further configured to monitor a distribution of locations in the reserve space table between the first data storage device and the second data storage device.
3. The data storage apparatus of claim 1 , wherein the first data storage device comprises one or more solid state drives.
4. The data storage apparatus of claim 1 , wherein the second data storage device comprises one or more hard disk drives.
5. The data storage apparatus of claim 1 , wherein the processor is further configured to prohibit data access operations to any location identified in the reserve space table.
6. A data storage apparatus comprising:
a processor;
a first data storage device connected to the processor, configured to store a reserve space table of unmapped data blocks; and
a second data storage device connected to the processor,
wherein:
the first data storage device has a relatively faster access time than the second data storage device;
the reserve space table is configured to identify discrete portions of the first data storage device and discrete portions of the second data storage device; and
the processor is configured to:
transfer data from a discrete portion of the second data storage device to a discrete portion of the first data storage device identified in the reserve space table;
after transferring data from the discrete portion, add the discrete portion of the second data storage device to the reserve space table and remove the discrete portion of the first data storage device from the reserve space table.
7. The data storage apparatus of claim 6 , wherein the processor is further configured to monitor a distribution of locations in the reserve space table between the first data storage device and the second data storage device.
8. The data storage apparatus of claim 7 , wherein the processor is further configured to:
transfer data from a plurality of discrete portions of the first data storage device to a plurality of discrete portions of the second data storage device when the distribution of locations in the reserve space table exceeds a threshold;
after transferring data from the plurality of discrete portions, add a plurality of locations, each associated with one of the plurality of discrete portions of the first data storage device to the reserve space table and remove a plurality of locations, each associated with one of the plurality of discrete portions of the second data storage device from the reserve space table.
9. The data storage apparatus of claim 8 , wherein the threshold is eighty percent of all locations identified in the reserve space table referencing a location on the second data storage device.
10. The data storage apparatus of claim 6 , wherein the processor is further configured to monitor a system usage metric.
11. The data storage apparatus of claim 10 , wherein the processor is further configured to:
transfer data from a plurality of discrete portions of the first data storage device to a plurality of discrete portions of the second data storage device when the system usage metric is below a threshold;
after transferring data from the plurality of discrete portions, add a plurality of locations, each associated with one of the plurality of discrete portions of the first data storage device to the reserve space table and remove a plurality of locations, each associated with one of the plurality of discrete portions of the second data storage device from the reserve space table.
12. The data storage apparatus of claim 6 , wherein the first data storage device comprises one or more solid state drives.
13. The data storage apparatus of claim 6 , wherein the second data storage device comprises one or more hard disk drives.
14. The data storage apparatus of claim 6 , wherein the processor is further configured to prohibit data access operations to any location identified in the reserve space table.
15. A method for migrating data between tiers in a data storage system, comprising:
transferring data from a discrete portion of a slow data storage device to discrete portion of a fast data storage device;
after transferring data from the discrete portion, adding the discrete portion of the slow data storage device to a reserve space table and removing the discrete portion of the fast data storage device from the reserve space table of unmapped data blocks.
16. The method of claim 15 , further comprising monitoring a distribution of locations in the reserve space table between the slow data storage device and the fast data storage device.
17. The method of claim 16 , further comprising:
transferring data from a plurality of discrete portions of the fast data storage device to a plurality of discrete portions of the slow data storage device when the distribution of locations in the reserve space table exceeds a threshold;
after transferring data from the plurality of discrete portions adding a plurality of locations, each associated with one of the plurality of discrete portions of the fast data storage device to the reserve space table and removing a plurality of locations, each associated with one of the plurality of discrete portions of the slow data storage device from the reserve space table.
18. The method of claim 17 , wherein the threshold is eighty percent of all locations identified in the reserve space table referencing a location on the slow data storage device.
19. The method of claim 15 , wherein the fast data storage device comprises one or more solid state drives.
20. The method of claim 15 , further comprising prohibiting data access operations to any location identified in the reserve space table.