Techniques for limiting the maximum storage consumed by a file system without shrinking an underlying volume
Techniques for limiting storage consumed by a file system without shrinking a volume upon which the file system is deployed. The techniques are employed in a clustered environment including multiple NAS nodes, each having access to block storage including multiple storage devices. By deploying the file system on a volume of a NAS node within the clustered environment, setting the value of the FS user size to be equal to the FS volume size, and if, at a later time, it is desired to reduce the file system size, setting the value of the FS user size to a lesser value than the FS volume size, IO requests received at the NAS node can be satisfied within the logical limit of the lesser value of the FS user size without shrinking the local volume, allowing the file system size to be reduced without requiring close coordination with the block storage.
1. A method of limiting the maximum data storage consumed by a file system, without shrinking a local volume upon which the file system is deployed, comprising:
deploying the file system on a local volume of a data storage node, the file system having a file system user size, and the local volume having a local volume size;
setting the file system user size to be equal to the local volume size;
determining that storage space requirements of the file system are less than the file system user size;
reducing the file system user size in accordance with the storage space requirements of the file system, without reducing the local volume size;
receiving, at the data storage node, a first write request to write first data to the file system;
determining whether the first write request can be satisfied within a logical limit of the reduced file system user size; and
having determined that the first write request cannot be satisfied within the logical limit of the reduced file system user size, performing one of:
(i) increasing the file system user size up to or less than the local volume size, without extending the local volume size;
(ii) extending the local volume size in accordance with the storage space requirements of the file system and setting the file system user size to be equal to the extended local volume size to obtain an increased file system user size; and
(iii) issuing a write failure indication with respect to the file system due to insufficient storage space.
2. The method of claim 1 further comprising:
receiving, at the data storage node, a second write request to write second data to the file system;
determining whether the second write request can be satisfied within a logical limit of the reduced file system user size; and
having determined that the second write request can be satisfied within the logical limit of the reduced file system user size, writing the second data to the file system deployed on the local volume.
3. The method of claim 1 further comprising:
performing, in a background process, a scavenging operation to un-map or de-allocate at least some address blocks within an address space of the local volume that were previously written to and subsequently freed.
4. The method of claim 1 further comprising:
having set the file system user size to be equal to the extended local volume size to obtain the increased file system user size:
determining whether the first write request can be satisfied within a logical limit of the increased file system user size; and
having determined that the first write request can be satisfied within the logical limit of the increased file system user size, writing the first data to the file system deployed on the local volume.
5. In a clustered storage environment, a data storage node connected to a host computer by a computer network, the data storage node comprising:
an interface to the computer network;
a memory; and
one or more processing units configured to execute one or more programs out of the memory:
to deploy a file system on a local volume of the data storage node, the file system having a file system user size, and the local volume having a local volume size;
to facilitate setting the file system user size to be equal to the local volume size;
to facilitate determining that storage space requirements of the file system are less than the file system user size;
to facilitate reducing the file system user size in accordance with the storage space requirements of the file system, without reducing the local volume size;
to receive a first write request to write first data to the file system;
to determine whether the first write request can be satisfied within a logical limit of the reduced file system user size; and
having determined that the first write request cannot be satisfied within the logical limit of the reduced file system user size, to perform one of:
(i) increasing the file system user size up to or less than the local volume size, without extending the local volume size;
(ii) facilitating setting the file system user size to be equal to an extended local volume size to obtain an increased file system user size, the local volume size being extended in accordance with the storage space requirements of the file system; and
(iii) issuing a write failure indication with respect to the file system due to insufficient storage space.
6. The data storage node of claim 5 wherein the one or more processing units are further configured to execute the one or more programs out of the memory:
to receive a second write request to write second data to the file system;
to determine whether the second write request can be satisfied within a logical limit of the reduced file system user size; and
having determined that the second write request can be satisfied within the logical limit of the reduced file system user size, to write the second data to the file system deployed on the local volume.
7. The data storage node of claim 5 wherein the one or more processing units are further configured to execute the one or more programs out of the memory to perform, in a background process, a scavenging operation to un-map or de-allocate at least some address blocks within an address space of the local volume that were previously written to and subsequently freed.
8. The data storage node of claim 5 wherein the one or more processing units are further configured to execute the one or more programs out of the memory:
having facilitated the setting of the file system user size to be equal to the extended local volume size to obtain the increased file system user size:
to determine whether the first write request can be satisfied within a logical limit of the increased file system user size; and
having determined that the first write request can be satisfied within the logical limit of the increased file system user size, to write the first data to the file system deployed on the local volume.
9. A computer program product including a set of non-transitory, computer-readable media having instructions that, when executed by control circuitry of a computerized apparatus, cause the control circuitry to perform a method of operating a file system, the method comprising:
deploying the file system on a local volume of a data storage node, the file system having a file system user size, and the local volume having a local volume size;
setting the file system user size to be equal to the local volume size;
determining that storage space requirements of the file system are less than the file system user size;
reducing the file system user size in accordance with the storage space requirements of the file system, without reducing the local volume size;
receiving, at the data storage node, a first write request to write first data to the file system;
determining whether the first write request can be satisfied within a logical limit of the reduced file system user size; and
having determined that the first write request cannot be satisfied within the logical limit of the reduced file system user size, performing one of:
(i) increasing the file system user size up to or less than the local volume size, without extending the local volume size;
(ii) extending the local volume size in accordance with the storage space requirements of the file system and setting the file system user size to be equal to the extended local volume size to obtain an increased file system user size; and
(iii) issuing a write failure indication with respect to the file system due to insufficient storage space.
10. The method of claim 9 further comprising:
receiving, at the data storage node, a second write request to write second data to the file system;
determining whether the second write request can be satisfied within a logical limit of the reduced file system user size; and
having determined that the second write request can be satisfied within the logical limit of the reduced file system user size, writing the second data to the file system deployed on the local volume.
11. The method of claim 9 further comprising:
performing, in a background process, a scavenging operation to un-map or de-allocate at least some address blocks within an address space of the local volume that were previously written to and subsequently freed.
12. The method of claim 9 further comprising:
having set the file system user size to be equal to the extended local volume size to obtain the increased file system user size:
determining whether the first write request can be satisfied within a logical limit of the increased file system user size; and
having determined that the first write request can be satisfied within the logical limit of the increased file system user size, writing the first data to the file system deployed on the local volume.