6.5 HP StoreAll OS User Guide

1) The segment server initiating the operation can read files directly from the segment
across the SAN; this is called a SAN READ.
2) The segment server initiating the operation routes writes over the IP network to the
segment server owning the segment. That server then writes data to the segment.
c. All reads and writes must be routed over the IP network between the segment servers.
8. Step 7 assumed that the server had to go to a segment to read a file. However, every segment
server that reads a file keeps a copy of it cached in its memory regardless of which segment
it was read from (in the diagram, two servers have cached copies of File 1). The cached
copies are used to service local read requests for the file until the copy is made invalid, for
example, because the original file has been changed. The file system keeps track of which
servers have cached copies of a file and manages cache coherency using delegations, which
are StoreAll file system metadata structures used to track cached copies of data and metadata.
File system building blocks
A file system is created from building blocks. The first block comprises an underlying physical
hardware RAID protected volume. Each volume is placed in a volume group (one volume per
volume group) and segments (logical volumes) are created from the volume groups. The system
administrator does not have to manage these low level operations. The built-in volume manager
handles the discovery of physical volumes, the creation of volume groups and the creation of logical
volumes as part of the process of creating a file system. It also assigns the ownership of segments
to servers in the cluster (File Serving Nodes).
Configuring file systems
You can configure your file systems to use the following features:
• Quotas. This feature allows you to assign quotas to individual users or groups, or to a directory
tree. Individual quotas limit the amount of storage or the number of files that a user or group
can use in a file system. Directory tree quotas limit the amount of storage and the number of
files that can be created on a file system located at a specific directory tree. By default, quotas
are enabled when you create and mount a file system using the GUI. If you use the CLI to
create and mount a file system, quotas are not enabled by default. If you do not enable quotas
when using the CLI to create and mount the file system and choose to enable quotas at a later
time, be aware this requires the file system to be unmounted first, which impacts system
availability. See “Configuring quotas” (page 30).
• Remote replication. This feature provides a method to replicate changes in a source file system
on one cluster to a target file system on either the same cluster or a second cluster. See “Using
remote replication” (page 292).
• Data retention and validation. Data retention ensures that files cannot be modified or deleted
for a specific retention period. Data validation scans can be used to ensure that files remain
unchanged. See “Managing data retention” (page 274).
• Antivirus support. This feature is used with supported Antivirus software, allowing you to scan
files on a StoreAll file system. See “Configuring Antivirus support” (page 346).
• StoreAll software snapshots. This feature allows you to capture a point-in-time copy of a file
system or directory for online backup purposes and to simplify recovery of files from accidental
deletion. Users can access the file system or directory as it appeared at the instant of the
snapshot. See “Creating StoreAll software snapshots” (page 357).
• Block Snapshots. This feature uses the array capabilities to capture a point-in-time copy of a
file system for online backup purposes and to simplify recovery of files from accidental deletion.
The snapshot replicates all file system entities at the time of capture and is managed exactly
like any other file system. See “Creating block snapshots” (page 367).
File system building blocks 13