PerformanceWiki [the blog]

IO Stack [PIC]

I/O stack components Overview

Typically the stack consists of the following
• Database
• Character or block device driver
• Multipathing driver
• SCSI driver
• HBA
• System Bus
• Switch/iSCSI routers
• Storage Array
• Disks
Example of vendors:

ASM-Database IBM Oracle
Character or block device driver
Multipathing driver – PowerPath, Windows MPIO
SCSI driver
HBA – Host Bus Adapter, Qlogic (IBM), Emulex
System Bus - PCI
Switch/iSCSI routers – Brocade, McData
Storage Array – IBM DS8100, EMC, HDS, HP
Disks - Seagate
The database processes makes I/O calls to the block device. The I/O scheduler in Linux forms the
interface between the generic block layer and the low level device drivers. The block layer provides
functions that are utilized by the file systems, databases (10gR2) and the virtual memory manager to submit I/O requests to block devices. These requests are transformed by the I/O scheduler and made available to the low-level device drivers. The device drivers consume the transformed requests and forward them (by using device specific protocols) to the actual device controllers that perform the I/O operations.