A Practical Hardware Sizing Guide for Sybase IQ

Local Store Devices
The current rule of thumb for determining the number of local store IQ devices (dbspaces) to
allocate for a single host IQ configuration should follow this algorithm:
IQ_dbspaces = 3 + ( number_of_singlehost_cores / 10 )
This number should be rounded up to the next highest whole number.
For example, a 4 core/CPU machine would need 3 + (4/10) or 3.4 devices. Rounded up, this
system should have a minimum of 4 devices for the local store.
IQ Device Placement
It is recommended, but not mandatory, that the IQ main and temporary store devices be
physically separated and not reside on the same LUNs and physical drives in the storage system.
Primarily, we want to increase overall throughput and placing these devices on the same hard
drives will cause thrashing. Secondarily, though, most storage systems have caching
mechanisms that can be tuned by device. This allows for tuning the drive array caches
differently for the different IQ device types.
For additional information on configuring storage devices, LUNs and, a SAN, search for “IQ
Reference Architecture Sizing Guide”, “Reference Architecture Implementation Guide”, and
“NonStopIQ” on the http://www.sybase.com website search box.
IQ Device Mapping
When developing the IQ storage subsystem, it is important to size the entire storage system
appropriately. It is also equally important for performance to segregate the workload between
filesystems, main store, and temporary store devices. The segregation should include separate
HBAs or I/O controllers as well as different paths through the SAN infrastructure. At the SAN,
the physical disks or spindles should also not be shared with any other application.
As an example, the following is a high level conceptual diagram of how the IQ storage could be
laid out. The IQ main store is comprised for 4 different RAID 5 groupings. Each RAID 5
grouping is a 5 disk RAID 5 (4+1 parity drive) configuration. The entire RAID group is presented
as a single device to any machine connected to the SAN so that they see the entire storage
content of those 4 disks (plus 1 for parity).
The RAID 5 “disk” is presented to the OS as a LUN. That LUN is, in turn, used by IQ as a single
dbspace. A logical volume manager (LVM) need not be present. If one is, it is the job of the
LVM to present the original LUN to IQ as a single disk that hasn‟t been striped together with
other devices.
It is also important to keep in mind that in a multi-node IQ configuration multiple hosts will need
to see the same IQ main store devices simultaneously. Adding ports and bandwidth to the SAN
and SAN switches will be critical to performance as more nodes are added.
Final
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