Filesystems, Object Stores & Filesystem Groups

This page describes the three types of entities relevant to data storage in the WekaIO system: filesystems, object stores and filesystem groups.

About Filesystems

A WekaIO filesystem is similar to a regular on-disk filesystem, with the key difference that it's distributed across all the hosts in the cluster. Consequently, in the WekaIO system, filesystems are not associated with any physical object, and are therefore nothing but a root directory with space limitations.

A total of up to 1024 filesystems are supported, all of which are equally and perfectly balanced on all SSDs and CPU cores assigned to the WekaIO system. This means that the allocation of a new filesystem, or the resizing a filesystem, are instant management operations that are performed instantly, and without any constraints.

Note: A filesystem group (see below) has to be created before creating a filesystem, and every filesystem must belong to one filesystem group.

A filesystem must have a defined capacity limit. A filesystem that belongs to a tiered filesystem group (see below) must have a total capacity limit and an SSD capacity limit. The total SSD capacity of all filesystems cannot exceed the total SSD capacity as defined in the total SSD net capacity.

Encrypted Filesystems

Both data at rest (residing on SSD and object store) and data in transit can be encrypted. This is achieved by enabling the filesystem encryption feature. A decision on whether a filesystem is to be encrypted is made when creating the filesystem.

Note: For proper security, selection of encryption should be used with a KMS (Key Management System). For integration information regarding your KMS, contact the WekaIO Support Team.

Note: It is only possible to enable encryption of data in a filesystem when the filesystem is created. Furthermore, enablement of the encryption feature on a filesystem cannot be cancelled.

Metadata Limitations

In addition to the capacity limitation, each filesystem also has a limitation on the amount of metadata. The system-wide metadata limit is determined by the SSD capacity allocated to WekaIO, as well as the RAM resources allocated to the WekaIO processes. By default, the metadata limit associated with a filesystem is proportional to the filesystem SSD size. It is possible to override this default by defining a filesystem-specific max-files parameter, although the total of the limits of the metadata for all the filesystems cannot exceed the total system metadata limits.

Metadata Calculations

Throughout this documentation, the metadata limitation per filesystem is referred to as a parameter named max-files , which really describes the number of metadata units, and not the number of files. This parameter encapsulates both the file count and the file sizes, as follows:

  • Each file requires two metadata units.

  • If a file exceeds 0.5 MB, an additional metadata unit is required.

  • For each additional 1 MB over the first one, an additional metadata unit is required.

For the purpose of the definitions above, it is irrelevant if the file is on the SSD or the object store.

For Example:

  • For a filesystem with potentially 1,000,000,000 files of 64 KB in size, 2,000,000,000 metadata units are required.

  • For a file system with potentially 1,000,000 files of 128 MB in size, 130,000,000 metadata units are required.

  • For a file system with 1,000,000 files of 750 KB in size, 3,000,000 metadata units are required.

About Object Stores

In the WekaIO system, object stores represent an optional external storage media, ideal for the storage of warm data. They can be purchased and configured independently by users (provided they support the S3 protocol) or supplied by WekaIO as part of the overall data storage solution. Object stores used in tiered WekaIO system configurations can be cloud-based, located in the same location or at a remote location.

Object stores are optimally used when a cost-effective data storage tier is required, at a price point which cannot be satisfied by server-based SSDs. An object store definition contains the object store DNS name, bucket identifier and access credentials. The bucket must be dedicated to the WekaIO system and must not be accessible by other applications. However, a single object store bucket may serve different filesystem groups, and even different filesystem groups that reside on different WekaIO systems.

About Filesystem Groups

In the WekaIO system, filesystems are grouped into up to 8 filesystem groups. Each filesystem group consists of a collection of filesystems which share a common connectivity to an object store system. This connectivity to object stores can be used in both the data lifecycle management and Snap to Object features.

A filesystem group may have a single object store associated with it, and multiple filesystem groups can be associated with the same object store. A filesystem group that has an associated object store can also define data lifecycle management parameters.

Each filesystem group may contain a data lifecycle management configuration and an object store definition, or alternatively be defined only to SSDs.

Filesystem Group Association to Object Stores

Once a filesystem group is connected to an object store, it cannot be disconnected from the object store or changed to a different bucket or object store. However, if reconfiguration of the object store identification information is required, such as changing connectivity definitions, DNS name, bucket name, access control parameters or the password, it can be edited, after which all the filesystem groups will work according to the new definitions. It is assumed that after such a change the same objects will still be available without any change.

Note: Each filesystem group has optional tiering control parameters (see Guidelines for Data Storage in Tiered WekaIO System Configurations).

Note: For information on managing these entities, refer to Managing Filesystems, Object Stores and Filesystem Groups.