Implementing coherency and page cache support in a distributed way for files
A plurality of computing devices are communicatively coupled to each other via a network, and each of the plurality of computing devices is operably coupled to one or more of a plurality of storage devices. The computing devices may use local caches in a coherent manner when accessing the plurality of storage devices.
1. A distributed storage system comprising:
a frontend computing device comprising a local memory, wherein at least a portion of the local memory is used as a cache memory;
a backend computing device; and
a plurality of storage devices, wherein the backend computing device provides a lease to the frontend computing device for the frontend computing device to access at least one of the plurality of storage devices, and wherein the lease comprises a token that is shared between the backend and the frontend, and wherein the token signals a usage by the frontend.
2. The system of claim 1 , wherein the cache memory comprises a read cache and a write cache.
3. The system of claim 2 , wherein the lease allows caching in one or both of the read cache and write cache.
4. The system of claim 1 , wherein the lease does not allow caching in the cache memory.
5. The system of claim 1 , wherein the local memory comprises random access memory (RAM).
6. The system of claim 5 , wherein the local memory comprises one or both of dynamic RAM (DRAM) and static RAM (SRAM).
7. The system of claim 1 , wherein the plurality of storage devices comprises flash memory.
8. The system of claim 1 , wherein the lease is for at least a portion of a file.
9. The system of claim 1 , wherein the lease is for a directory.
10. The system of claim 1 , wherein the backend computing device provides the lease in response to the frontend computing device submitting a lease request to the backend computing device.
11. The system of claim 10 , wherein the lease request comprises a lease capability.
12. The system of claim 1 , wherein the frontend computing device is configured to submit a lease renewal request to the backend computing device, and the lease renewal request comprises a renewal lease capability.
13. The system of claim 12 , wherein the backend computing device is configured to provide a lease renewal when the renewal lease capability is the same as an initial lease capability of the lease.
14. The system of claim 1 , wherein the backend computing device is configured to determine that the frontend computing device does not need the lease, and upon determining that the frontend computing device does not need the lease, the backend computing device is configured to revoke the lease.
15. The system of claim 1 , wherein the frontend computing device is configured to relinquish the lease upon determining that it does not need the lease.
16. A method for using a distributed storage system, comprising:
requesting, by a frontend computing device to a backend computing device, a lease to access a plurality of storage devices using a local cache of the frontend computing device; and
providing, by the backend computing device, a lease to access the plurality of storage devices, wherein the lease comprises a token that is shared between the backend and the frontend, and wherein the token signals a usage by the frontend.
17. The method of claim 16 , wherein the lease is one of: for at least a portion of a file in the plurality of storage devices, or for a directory in the plurality of storage devices.
18. The method of claim 16 , comprising the frontend computing device submitting a lease renewal request to the backend computing device.
19. The method of claim 16 , comprising relinquishing, by the frontend computing device, the lease upon determining that it does not need to access the plurality of storage devices.
20. The method of claim 16 , comprising revoking, by the backend computing device, the lease upon determining that the frontend computing device does not need to access the plurality of storage devices.