An array is a set of physical disk drives that may be combined or subdivided into logical drives distributed across all disks in the set. The advantages of a drive array implementation are:
+ Effective high-speed data transfer rates
+ Ability to handle simultaneous multiple requests
+ Increased storage capacity
+ Flexibility in configuring data
+ High reliability
Drive array configuration information is stored on the drives, on the system board NVRAM, and on the array controller NVRAM. This allows the controller to be changed without requiring reconfiguring. It further allows a set of configured hard drives to be moved from one machine to another without data loss.
+ Effective high-speed data transfer rates
+ Ability to handle simultaneous multiple requests
+ Increased storage capacity
+ Flexibility in configuring data
+ High reliability
Drive array configuration information is stored on the drives, on the system board NVRAM, and on the array controller NVRAM. This allows the controller to be changed without requiring reconfiguring. It further allows a set of configured hard drives to be moved from one machine to another without data loss.
Arrays provide the following features:
Data striping across multiple drives. A file is divided into a selected number of sectors and then written across a series of drives. The process of writing (or reading) a file across multiple drives is much faster.
Multiple channels. The drive array has up to four channels that can be used at the same time, thus increasing performance.
Data striping across multiple drives. A file is divided into a selected number of sectors and then written across a series of drives. The process of writing (or reading) a file across multiple drives is much faster.
Multiple channels. The drive array has up to four channels that can be used at the same time, thus increasing performance.
Request processing. Because multiple commands can be issued across multiple devices, the commands can be processed at the same time and the requests are processed in the most logical order (Tagged Command Queuing).
Although there are several levels defined by the RAID model, HP Array Controllers support only six.
• RAID 0 Data Striping without Parity
• RAID 1 Disk Mirroring
• RAID 2 Complex Error Correction
• RAID 3 Parallel-Transfer, Parity Drive
• RAID 4 Concurrent Access, Dedicated Parity Drive (Data Guarding)
• RAID 5 Concurrent Access, Distributed Parity (Distributed Data Guarding)
• RAID 1+0 Disk Mirroring and Data Striping without Parity
• RAID ADG Advanced Data Guarding with Two Sets of Parity; ADG is sometimes called RAID 6.
The following pages describe these levels in detail.
• RAID 0 Data Striping without Parity
• RAID 1 Disk Mirroring
• RAID 2 Complex Error Correction
• RAID 3 Parallel-Transfer, Parity Drive
• RAID 4 Concurrent Access, Dedicated Parity Drive (Data Guarding)
• RAID 5 Concurrent Access, Distributed Parity (Distributed Data Guarding)
• RAID 1+0 Disk Mirroring and Data Striping without Parity
• RAID ADG Advanced Data Guarding with Two Sets of Parity; ADG is sometimes called RAID 6.
The following pages describe these levels in detail.
RAID Level 0 – Data Striping without Parity
In RAID 0, data striping without parity, a file is broken into stripes (or segments) and written across multiple disks. Striping unites multiple physical drives into a single logical drive. The logical drive is arranged so blocks of data are written alternately across all physical drives in the logical array. The number of sectors per block is referred to as the striping factor.
By definition, RAID 0 requires two of more drives for a true stripe set. However, with HP array controllers, a RAID 0 logical volume can be created with a single drive.
In RAID 0, data striping without parity, a file is broken into stripes (or segments) and written across multiple disks. Striping unites multiple physical drives into a single logical drive. The logical drive is arranged so blocks of data are written alternately across all physical drives in the logical array. The number of sectors per block is referred to as the striping factor.
By definition, RAID 0 requires two of more drives for a true stripe set. However, with HP array controllers, a RAID 0 logical volume can be created with a single drive.
The above illustration shows how a file is broken into stripes (or segments) and then written across multiple disks. This greatly improves the disk latency (the amount of time a disk head has to wait for the target sector to move under the head). In addition, 100 percent of the disk space is available for data and overall disk performance is improved.
RAID Level 1 – Disk Mirroring
With RAID 1, data is written to two separate mirrored drives. If a drive should fail, the mirrored drive is the safeguard. RAID 1 requires an even number of drives, with a maximum of 30 when connected to dual-channel controllers supporting the Wide-Ultra SCSI-3 or Wide-Ultra2 protocols. Drives must also be
added in pairs to achieve a RAID 1 expansion.
RAID 1 mirrors the entire data structure on different drives, and allows split seeks. When reading data from the drives, the drive or drives with the requested data nearest to the read/write heads will be read. This improves read performance slightly.
With RAID 1, data is written to two separate mirrored drives. If a drive should fail, the mirrored drive is the safeguard. RAID 1 requires an even number of drives, with a maximum of 30 when connected to dual-channel controllers supporting the Wide-Ultra SCSI-3 or Wide-Ultra2 protocols. Drives must also be
added in pairs to achieve a RAID 1 expansion.
RAID 1 mirrors the entire data structure on different drives, and allows split seeks. When reading data from the drives, the drive or drives with the requested data nearest to the read/write heads will be read. This improves read performance slightly.
Although RAID 1 is a viable fault-tolerant solution, it is an expensive solution in that it requires twice as much drive storage (only 50 percent of the total disk space is available for data storage).
RAID Level 5 – Distributed Data Guarding
In RAID 5, data is striped across multiple drives, its parity sum is calculated, and the parity sum is also striped across multiple drives (not a dedicated parity drive). This increases performance in that the parity generation does not cause degradation, as not all drives need access to a single parity drive.
In RAID 5, data is striped across multiple drives, its parity sum is calculated, and the parity sum is also striped across multiple drives (not a dedicated parity drive). This increases performance in that the parity generation does not cause degradation, as not all drives need access to a single parity drive.
RAID 5 is best suited for I/O-intensive applications and transaction processing, thus making it an ideal solution for high-performance faulttolerant servers. The biggest limitation of RAID 5 is the increased read time in a failure. Regardless of which disk fails data has to be recalculated on each read from the remaining disks.
RAID 5 has the same drive requirements as RAID 4, except that the space used for parity is distributed across all the drives in the volume.
RAID 5 has the same drive requirements as RAID 4, except that the space used for parity is distributed across all the drives in the volume.
RAID Level 1+0
RAID 1+0 is a combination of striping and mirroring data. RAID 1+0 writes data across the drives in the same fashion as RAID 0, and achieves redundancy by mirroring data similar to RAID 1. Unlike RAID 1, the data disks are also the mirror disks. RAID 1+0 mirrors data back onto the data disks rotated by one drive. An odd number of drives can be used in a RAID 1+0 configuration, whereas RAID 1 requires an even number of drives.
You can continue to access data in a RAID 1+0 configuration with a single drive failure or multiple drive failures. As long as 1 drive of each mirrored pair is functioning, the set will function.
You can continue to access data in a RAID 1+0 configuration with a single drive failure or multiple drive failures. As long as 1 drive of each mirrored pair is functioning, the set will function.
RAID 6 Advanced Data Guarding (ADG)
RAID ADG delivers high fault tolerance similar to RAID 1 while keeping capacity utilization high like RAID 5. It protects data from multiple drive failures with an ability to withstand two simultaneous hard drive failures without data loss or downtime. To accomplish this, RAID ADG increases to two the number of sets of parity striped across the disks. This method results in protection for an array with as many as 56 drives while requiring the capacity of only two drives to store parity information.
RAID ADG delivers high fault tolerance similar to RAID 1 while keeping capacity utilization high like RAID 5. It protects data from multiple drive failures with an ability to withstand two simultaneous hard drive failures without data loss or downtime. To accomplish this, RAID ADG increases to two the number of sets of parity striped across the disks. This method results in protection for an array with as many as 56 drives while requiring the capacity of only two drives to store parity information.
Smart Array controller overview
HP SCSI Managed Array Technology (SMART) Array controllers provide hardware level RAID support. The SMART Array controller accepts write commands, calculates any parity data, decides where the data and the parity data are to be written, then manages the writing of that data. Taking that overhead away from the operating system and giving it to the array controller speeds read and writes operations. This hardware also provides fault tolerant features that protect data integrity.
HP SCSI Managed Array Technology (SMART) Array controllers provide hardware level RAID support. The SMART Array controller accepts write commands, calculates any parity data, decides where the data and the parity data are to be written, then manages the writing of that data. Taking that overhead away from the operating system and giving it to the array controller speeds read and writes operations. This hardware also provides fault tolerant features that protect data integrity.
HP Smart Array controllers have a number of features that enhance their performance, reliability and serviceability. The following is a list of features that are represented within the product line. Consult individual controller specifications for those that apply to a particular model.
Inter-generation data compatibility for ease of migration
Standard configuration and management tools across product line
Automatic data transfer from a failed drive to an online spare
Redundant ROM protection against firmware image corruption
Pre-failure notification of impending hard disk failure
Capacity expansion allows the addition of drives to an existing array
Volume extension increases the space on an existing logical drive
RAID migration allows online reconfiguration to a new level of fault tolerance
Stripe size migration to tune performance
Inter-generation data compatibility for ease of migration
Standard configuration and management tools across product line
Automatic data transfer from a failed drive to an online spare
Redundant ROM protection against firmware image corruption
Pre-failure notification of impending hard disk failure
Capacity expansion allows the addition of drives to an existing array
Volume extension increases the space on an existing logical drive
RAID migration allows online reconfiguration to a new level of fault tolerance
Stripe size migration to tune performance
Smart Array Controller Features Summary
Configuration utilities for Smart Array controllers include
+ Option ROM Configuration for Arrays (ORCA) – an off-line ROMbased configuration utility that runs independent of the operating system. ORCA can be started during the boot process and uses a menu-driven
interface for minimal configuration needs by experienced users. ORCA is accessible by pressing F8 after system POST. It allows the user to create and delete logical drives and to set the boot controller order.
ORCA does not support drive expansion, RAID level migration and stripe size migration. Smart Array controllers with ORCA Support include
all embedded RAID controllers (ROC, 5i, 5i plus, future products)
all 5th generation Smart Array controllers (532, 5302, 5304, 5312)
all future Smart Array generations
+ Array Configuration Utility (ACU) – a configuration utility that can be run or installed from SmartStart 5.5 or earlier. ACU has a graphical interface for extensive configuration needs. Wizards are available to support novice users. The Array Configuration Utility (ACU) simplifies array configuration. ACU can be started from within the OS, from the SmartStart CD or from a bootable diskette. Under Windows 2000, Windows NT and Novell Netware this utility can be started online. The server does not have to be powered down when disks are configured.
+ Array Configuration Utility XE (ACU-XE) – a browser-based utility that has both wizard-based assistance and different operating modes for different skill levels or faster configuration.
+ Option ROM Configuration for Arrays (ORCA) – an off-line ROMbased configuration utility that runs independent of the operating system. ORCA can be started during the boot process and uses a menu-driven
interface for minimal configuration needs by experienced users. ORCA is accessible by pressing F8 after system POST. It allows the user to create and delete logical drives and to set the boot controller order.
ORCA does not support drive expansion, RAID level migration and stripe size migration. Smart Array controllers with ORCA Support include
all embedded RAID controllers (ROC, 5i, 5i plus, future products)
all 5th generation Smart Array controllers (532, 5302, 5304, 5312)
all future Smart Array generations
+ Array Configuration Utility (ACU) – a configuration utility that can be run or installed from SmartStart 5.5 or earlier. ACU has a graphical interface for extensive configuration needs. Wizards are available to support novice users. The Array Configuration Utility (ACU) simplifies array configuration. ACU can be started from within the OS, from the SmartStart CD or from a bootable diskette. Under Windows 2000, Windows NT and Novell Netware this utility can be started online. The server does not have to be powered down when disks are configured.
+ Array Configuration Utility XE (ACU-XE) – a browser-based utility that has both wizard-based assistance and different operating modes for different skill levels or faster configuration.
Selecting the Server diagnostics utility from the Maintenance menu brings you to a sub menu with another set of tabs labeled Survey, Test, Status, Log and Help. The Survey tab is automatically selected when the screen displays and provides a detailed view of the system components. Survey is a utility that has evolved from a command line application to a web-based version and is now a key element of HP Insight Diagnostics that comes on the SmartStart 6.x CD. Survey is therefore available on all generation 2 and later ProLiant servers.
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