HP Xw8200 Hardware versus Software RAID on Linux Workstations - Page 2

Introduction This document will discuss a variety of factors to consider when choosing between hardware and software RAID configurations on Linux workstations. Comparison Hardware RAID versus software RAID in regards to a variety of considerations. System Performance • Hardware RAID may better balance system performance through asynchronous performance and offloading of processors, although there may be performance losses due to issues such as PCI resource conflicts. However, with modern processing capabilities, there is usually no performance loss seen with a software RAID solution. • System performance also depends on other factors such as other hardware being used, processor speeds, or RAID level. Storage Performance • Software RAID usually performs better than hardware RAID in terms of raw disk performance. This is especially true in systems with multiple processors, whether this be multiple physical processors or dual-core systems. The RAID level being used does not generally have an effect on storage performance. • Software RAID generally offers higher peak performance than hardware RAID and this can be improved more by the quality of hardware used. Management/Maintenance • One of the biggest reasons for using hardware RAID is the availability of management tools provided by the hardware controllers/drivers. Hardware RAID provides support for array management via provided tools. With software RAID, these sorts of management procedures must be performed manually, which can be more daunting for users who are less comfortable with the inner workings of their operating system. Features • Hardware RAID controllers usually come with a variety of useful features such as a dedicated XOR engine, automatic RAID migration support, online capacity expansion, hot swaps and hot spares, and battery backup. Sometimes, common RAID maintenance procedures can be completed automatically with hardware RAID; this is a matter of convenience for users. Flexibility • Software RAID is generally more flexible in terms of using a variety of hard disks and controllers, including ones that have never been qualified together. • Software RAID allows the use or mixing of more block device types, whereas hardware RAID is usually constrained to a single disk type. • Software RAID also allows for more RAID levels through layering, while hardware RAID is constrained to whatever subset of levels the hardware manufacturer decides to support. 2