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OLAP - Sequential I/O, Read intensive
OLTP - Random I/O, Read /Write intensive
Calculating the number of disks required
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1. the required disk I/O per second
2. I/O per second capacity (IOPS) of the individual disks included
Required # Disks = (Reads/sec + (Writes/sec * RAID adjuster)) / Disk IOPS
Remember to separate the transaction log and data files.
RAID = Redundant Array of Independent Disks
RAID0 - zero redundancy RAID (not recommended)
RAID1 - disk mirroring, 50% disk utilization level, write medium, read high
RAID5 - disk utilization equals 1 - (1/N), write low, read high, minimum three drives
SAN - Storage Area Network
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*Multiple servers can connect to a SAN via special host bus adapter (HBA) cards
installed in each connecter server.
*Disks within the SAN are grouped together into logical unit numbers (LUNs)
and presented as required to connected servers. The server sees the LUN as a locally attached disk.
*Major benefits of a SAN is sharing disks among many servers to maximize usage.
*To get best performance dedicate the entire SAN to a single, mission critical database.
If your organization decides on a SAN storage system have a good working relationship with your SAN administrator.
Each physical disk in a SAN can be carved up into parts and used in the creation of separate LUNs.
As a result, LUNs from many servers can all be using different parts of the same physical disks.
