Comparing Intel Hardware and Software RAID solutions

ManualsBrandsIntel ManualsOtherIntel Server Board S2600CP4

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Performance

In the past, a primary reason not to use software RAID was

because it impacted the overall system performance since it

requires the additional CPU cycles to perform RAID

operations. But, with today’s powerful CPUs, overall

software RAID performance can be comparable to hardware

RAID for typical benchmarks and in some real-life internal

storage solutions.

When comparing write I/O response times (i.e. latency),

however, hardware RAID is up to 5 to 100 times quicker than

software RAID due to write back caching on hardware RAID

controllers. The lower latencies of hardware RAID are very

important for streaming applications like video surveillance.

Because of the long I/O response times of software RAID,

streaming applications pile up data in cache

(latency x throughput = cached data). Using software RAID

in these applications increases the chance of losing cached

data in the event of a server or OS failure.

Advanced Feature Set

The ﬁrmware existing on hardware RAID allows for advanced algorithms that are not easily made available for software

RAID. These features include RAID 6, revertible hot-spare, advanced array migration or capacity expansion, and higher

physical device limits. For many customers, these features alone may result in a preference for hardware RAID; rather

than software RAID.

Server Virtualization

When using server virtualization, a hot trend in Enterprise IT, hardware RAID has distinct advantages over software RAID.

Server virtualization allows a single server to emulate several smaller (presumably older) servers. Software RAID would require

a unique instance of the software RAID stack to be implemented on each virtual server. This could be costly, administratively

heavy, and overly complex. Because hardware RAID utilizes a dedicated CPU and on-board cache, and connects to the physical

server via the PCI Express bus, I/O requests from virtual servers are considerably less complex.

Example: Comparison of IO Response times (64KB random

write single burst - lower is better)

Software RAID

0.90 ms

13.5 ms

Small Burst – 50 IOs

Large Burst – 200 IOs

Hardware RAID

0.17 ms

Usage Model Examples

Application server; data

stored elsewhere

Web/Media-server

Video editing

General purpose small business server

Entry-level small business server

Database-Server, File-Server,

Mail-Server

Database-Server, File-Server,

Mail-Server

Video Surveillance

Main Requirements

Basic Reliability

Large Capacity with Basic Reliability

Large Capacity with Basic Reliability;

minimal impact on CPU

Data safety

Low cost

High Availability

High Availability and High

Performance

Maximum Throughput & Capacity

with High Reliability

Type of RAID

HW RAID or SW RAID

HW RAID

HW RAID or SW RAID

HW RAID

RAID Level

RAID 1

RAID 5

RAID 5/50

RAID 10/ 5

RAID 1

RAID 5/50

RAID 10

RAID 6/60

HDD Type

SATA or SAS

SATA

SAS or SATA

SATA

SAS or SATA

SAS

SAS or SATA

*For the purposes of this paper, all references to software RAID denote Intel® Embedded Server RAID technology II available on all Intel® Server Boards based on Intel

Server Chipset S5000. All references to hardware RAID denote Intel® RAID controllers powered by LSI MegaRAID* technology.