PDF《Software RAID》

Dell White Paper September,

2009 Software RAID Functionality on Dell Value Line Servers By Priyanka Singh Keerthi Ganapathi Nagaraju Chinta Dell White Paper September,

2009 This white paper is for informational purposes only.

Dell reserves the right to make changes without further notice to any products herein. The content provided is as is and without express or implied warranties of any kind. Dell White Paper September,

2009 Table of Contents

1 Introduction.1

2 Software RAID in Dell Servers.1

3 PERC S100 Implementation

2 4 PERC S300 Implementation

2 5 Features of Software RAID.3

6 SW RAID Integration with Dell Storage Management Software

4 6.1 Device Discovery.4 6.2 Consistency Check.4 6.3 Create Virtual Disk.4 6.3.1 RAID Levels Supported

4 6.3.2 Protocol and Media Type Mixing.4 6.3.3 Background Initialization.5 6.3.4 Drive Rules.5 6.3.5 Stripe Size.5 6.3.6 Rebuild

5 6.3.7 Reconfigure.5 6.3.8 Spare Assignment

5 6.4 Event Management and Monitoring

5 7 Advantages of Software RAID Solution.5 Dell White Paper September,

2009 1 Software RAID Functionality on Dell Value Line Servers

1 Introduction The new PowerEdge T110, R210, T310, and R510 Servers from Dell have new RAID software. This white paper discusses the architecture, advantages, implementation in the Dell value line servers and the usage. The operating system (OS) driver software is responsible for the software RAID operations, and the RAID task runs on the CPU of the system. RAID runs the kernel disk code. Software (SW) RAID solutions are low-cost and entry-level solutions that offer major advantages over the existing hardware RAID solution in value line servers. They are positioned for SMB servers. This gives the hard disks increased performance with minimal hardware. Software RAID in Dell value line serves is implemented in two ways. ? Minimal RAID: This pure software solution (PERC S100) leverages the I/O controller hub (ICH) chipset on the platform motherboard, which enables a SATA-only competitive solution at no extra cost. ? Value RAID: This is a hybrid solution with a SAS IOC HBA option and SW RAID (PERC S300) offered as a SAS/SATA solution upgrade. The hardware helps to overcome some of the weaknesses of pure software RAID. Such solutions usually come with additional hardware.

2 Software RAID in Dell Servers Figure 1. Data Flow from Application to PERC S100/S300 PERC S100/PERC S300 Option ROM is an interface that creates a RAID such as initializing the disks, which stores the RAID specific metadata on the selected hard disks that would be part of the RAID. At this point, the RAID specified by the user in the option ROM is not fully active. The RAID becomes active as soon as the OS has loaded the RAID driver software. All the RAID management tasks can only be done when the OS is installed. After the OS is loaded, user application sends the DATA for processing to the CPU because all the RAID Operations in a software RAID uses system CPU Cycles. This is because the software RAID controllers do not have the intelligence to perform RAID operations. System CPU processes the DATA Users and Applications Data CPU Raw Disk Blocks Write Read Disk Controller (No RAID Controller) Software RAID Dell White Paper September,

2009 2 Software RAID Functionality on Dell Value Line Servers and performs read/write operations to and from the disk. It also sends the data blocks into the disks. The controller stores the data blocks, as well as the addresses where the data has to be stored, onto the hard disks. The virtual disks (VD) created in one system can be moved to another system with the same configuration if the controller (PERC S100 /PERC S300) is the same in both systems.