SAS Scalable Performance Data Server 4.5, Administrator'S Manual

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To ensure reliability, data table space is typically organized into RAID 1+0 or RAID-5 disk
configurations. Very large warehouses should consider a RAID-5 configuration with a
second storage array to mirror the data.
Index Table Space
When a domain is declared in a LIBNAME statement, index tables are stored in the space
defined in the PATHNAME= specification, unless the INDEXPATH= option is specified.
The PATHNAME= space is designed to contain metadata tables for a domain, but it can
also contain index tables. As a domain's size and complexity increases, so do the benefits
for organizing index tables into their own INDEXPATH= space.
Index space typically does not require the high-level scalability that data space, temporary
table space, or work spaces need for I/O performance. When a process is using an index,
the read access pattern is very different from a parallel I/O pattern of data or multiple user
patterns against data.
Index space is typically configured as a large striped file system across a large number of
disks and I/O channels. A typical configuration such as RAID 1+0 or RAID 5 will support
some type of redundancy to ensure index space availability.
Metadata Table Space
When a domain is declared in a LIBNAME statement, metadata tables are stored in the
space defined in the PATHNAME= specification. If the space configured in PATHNAME=
fills, SPD Server stores overflow metadata for existing tables in the space defined in the
optional METAPATH= specification, if it is declared. The PATHNAME= and
METAPATH= spaces are specifically designed to contain metadata tables for a domain.
Compared to the other space categories, metadata space is relatively small and usually does
not require scalability. If compressed data in a given warehouse uses 10 terabytes of disk
space, there will be approximately 10 gigabytes of metadata.
As a rule of thumb, when setting up metadata space, plan to allot 20 gigabytes of metadata
space for every 10 terabytes of physical data disk space. When new data paths are added
to expand a server, additional metadata space should be added within the primary path of
the server.
A table's metadata becomes larger when there are rows in the table that are marked as
deleted. Bitmaps are stored in the metadata that is used to filter the deleted rows. The space
required depends on the number of rows deleted and on their distribution within the table.
Although the space required for the metadata is small, the setup and configuration of the
disk space is very important. The disk space must be expandable, mirrored, and backed up.
Work File Space
SPD Server administrators use statements in the body of the spdsserv.parm file to reserve
a space for intermediate calculations and temporary files. The work space that is configured
in
spdsserv.parm is shared by all SPD Server users.
Some SPD Server users have data needs that might be constrained by using the common
intermediate calculation and file space reserved for all users. SPD Server administrators
can use the
libnames.parm file to create and reserve a work space that is specifically
associated with a single domain and its approved users. This presents improvement
opportunities for both security and performance. As a domain's size and complexity
increases, so do the benefits for organizing temporary and intermediate tables into their
own workspace defined by WORKPATH=.
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Chapter 12 • Setting Up SPD Server Libname Parameter Files