StorNext uses Stripe Groups to separate data with different characteristics onto different LUNs. Every StorNext file system has three kinds of Stripe Groups.
- Metadata Stripe Groups hold the file system metadata: the file name and attributes for every file in the file system. Metadata is typically very small and accessed in a random pattern.
- Journal Stripe Groups hold the StorNext Journal: the sequential changes to the file system metadata. Journal data is typically a series of small sequential writes and reads.
- User Data Stripe Groups hold the content of files. User data access patterns depend heavily on the customer workflow, but typical StorNext use is of large files sequentially read and written. Users can define multiple User Data Stripe Groups with different characteristics and assign data to those Stripe Groups with Affinities; see StorNext File System Stripe Group Affinity.
See FSBlockSize, Metadata Disk Size, and JournalSize Settings for additional information about how to determine the size of a stripe group.
Because the typical access patterns for Metadata and User Data are different, Quantum recommends that you create different stripe groups for metadata and user data. The journal data access patterns are similar enough to be placed on the Metadata Stripe Group.
To achieve optimal performance, Quantum recommends you split apart the data, the metadata, and the journal data into separate stripe groups. The create, remove, and allocate (for example, write) operations are very sensitive to I/O latency of the journal stripe group. However, if create, remove, and allocate performance are not critical, then you can share a stripe group for both metadata and journal. You must set the exclusive property on the metadata and journal stripe group so that it does not get allocated for user data as well.
Note: Quantum recommends that you have only a single metadata stripe group. For increased performance, use multiple LUNs (two or four) for the stripe group.
The access patterns on an High Availability (HA) shared file system allows for sharing of metadata, journal and user data on a single stripe group. Some appliances might have a single stripe group for the HA shared file system pre-configured from the factory. If you expand an HA shared file system configured as a single stripe group, you must add either:
- Another shared metadata, user data stripe group.
- An exclusive metadata stripe group and a data stripe group.
Caution: You cannot add an exclusive user data stripe group.
