Ibm Sas Disk Array Manager Download
Thibaut Silverman
RAID (redundant array of independent disks) is a way of storing the same data in different places on multiple hard disks or solid-state drives (SSDs) to protect data in the case of a drive failure. There are different RAID levels, however, and not all have the goal of providing redundancy.
RAID works by placing data on multiple disks and allowing input/output (I/O) operations to overlap in a balanced way, improving performance. Because using multiple disks increases the mean time between failures, storing data redundantly also increases fault tolerance.
RAID employs the techniques of disk mirroring or disk striping. Mirroring will copy identical data onto more than one drive. Striping partitions help spread data over multiple disk drives. Each drive's storage space is divided into units ranging from a sector of 512 bytes up to several megabytes. The stripes of all the disks are interleaved and addressed in order. Disk mirroring and disk striping can also be combined in a RAID array.
In a single-user system where large records are stored, the stripes are typically set up to be small (512 bytes, for example) so that a single record spans all the disks and can be accessed quickly by reading all the disks at the same time.
A RAID controller is a device used to manage hard disk drives in a storage array. It can be used as a level of abstraction between the OS and the physical disks, presenting groups of disks as logical units. Using a RAID controller can improve performance and help protect data in case of a crash.
A RAID controller may be hardware- or software-based. In a hardware-based RAID product, a physical controller manages the entire array. The controller can also be designed to support drive formats such as Serial Advanced Technology Attachment and Small Computer System Interface. A physical RAID controller can also be built into a server's motherboard.
RAID 1. Also known as disk mirroring, this configuration consists of at least two drives that duplicate the storage of data. There is no striping. Read performance is improved, since either disk can be read at the same time. Write performance is the same as for single disk storage.
RAID 2. This configuration uses striping across disks, with some disks storing error checking and correcting (ECC) information. RAID 2 also uses a dedicated Hamming code parity, a linear form of ECC. RAID 2 has no advantage over RAID 3 and is no longer used.
RAID 5. This level is based on parity block-level striping. The parity information is striped across each drive, enabling the array to function, even if one drive were to fail. The array's architecture enables read and write operations to span multiple drives. This results in performance better than that of a single drive, but not as high as a RAID 0 array. RAID 5 requires at least three disks, but it is often recommended to use at least five disks for performance reasons.
RAID 5 arrays are generally considered to be a poor choice for use on write-intensive systems because of the performance impact associated with writing parity data. When a disk fails, it can take a long time to rebuild a RAID 5 array.
RAID 6. This technique is similar to RAID 5, but it includes a second parity scheme distributed across the drives in the array. The use of additional parity enables the array to continue functioning, even if two disks fail simultaneously. However, this extra protection comes at a cost. RAID 6 arrays often have slower write performance than RAID 5 arrays.
RAID 03 (RAID 0+3, also known as RAID 53 or RAID 5+3). This level uses striping in RAID 0 style for RAID 3's virtual disk blocks. This offers higher performance than RAID 3, but at a higher cost.
Adaptive RAID. This level enables the RAID controller to decide how to store the parity on disks. It will choose between RAID 3 and RAID 5. The choice depends on what RAID set type will perform better with the type of data being written to the disks.
Linux MD RAID 10. This level, provided by the Linux kernel, supports the creation of nested and nonstandard RAID arrays. Linux software RAID can also support the creation of standard RAID 0, RAID 1, RAID 4, RAID 5 and RAID 6 configurations.
As with RAID controllers, RAID is implemented through either hardware or software. Hardware-based RAID supports different RAID configurations and is especially well suited for RAID 5 and 6. Configuration for hardware RAID 1 is good for supporting the boot and application drive process, while hardware RAID 5 is appropriate for large storage arrays. Both hardware RAID 5 and 6 are well suited for performance.
The term RAID was coined in 1987 by David Patterson, Randy Katz and Garth A. Gibson. In their 1988 technical report, "A Case for Redundant Arrays of Inexpensive Disks (RAID)," the three argued that an array of inexpensive drives could beat the performance of the top expensive disk drives of the time. By using redundancy, a RAID array could be more reliable than any one disk drive.
While this report was the first to put a name to the concept, the use of redundant disks was already being discussed by others. Geac Computer Corp.'s Gus German and Ted Grunau first referred to this idea as MF-100. IBM's Norman Ken Ouchi filed a patent in 1977 for the technology, which was later named RAID 4. In 1983, Digital Equipment Corp. shipped the drives that would become RAID 1, and in 1986, another IBM patent was filed for what would become RAID 5. Patterson, Katz and Gibson also looked at what was being done by companies such as Tandem Computers, Thinking Machines and Maxstor to define their RAID taxonomies.
While the levels of RAID listed in the 1988 report essentially put names to technologies that were already in use, creating common terminology for the concept helped stimulate the data storage market to develop more RAID array products.
RAID is not quite dead, but many analysts say the technology has become obsolete in recent years. Alternatives such as erasure coding offer better data protection -- albeit, at a higher price -- and have been developed with the intention of addressing the weaknesses of RAID. As drive capacity increases, so, too, does the chance for error with a RAID array, and capacities are consistently increasing.
The rise of SSDs is also seen as alleviating the need for RAID. SSDs have no moving parts and do not fail as often as hard disk drives. SSD arrays often use techniques such as wear leveling instead of relying on RAID for data protection. Modern SSDs are fast enough that modern servers may not need the slight performance boost that RAID offers. However, they still may be currently used to prevent data loss.
The Atropos logical volume manager allows applications to exploit characteristics of its underlying collection of disks. It stripes data in track-sized units and explicitly exposes the boundaries, allowing applications to maximize efficiency for sequential access patterns even when they share the array. Further, it supports efficient diagonal access to blocks on adjacent tracks, allowing applications to orchestrate the layout and access to two-dimensional data structures, such as relational database tables, to maximize performance for both row-based and column-based accesses.
A disk array controller is a device that manages the physical disk drives and presents them to the computer as logical units. It almost always implements hardware RAID, thus it is sometimes referred to as RAID controller. It also often provides additional disk cache.
In a modern enterprise architecture disk array controllers (sometimes also called storage processors, or SPs[1]) are parts of physically independent enclosures, such as disk arrays placed in a storage area network (SAN) or network-attached storage (NAS) servers.
Those external disk arrays are usually purchased as an integrated subsystem of RAID controllers, disk drives, power supplies, and management software. It is up to controllers to provide advanced functionality (various vendors name these differently):
A simple disk array controller may fit inside a computer, either as a PCI expansion card or just built onto a motherboard. Such a controller usually provides host bus adapter (HBA) functionality itself to save physical space. Hence it is sometimes called a RAID adapter.
Some other operating systems have implemented their own generic frameworks for interfacing with any RAID controller, and provide tools for monitoring RAID volume status, as well as facilitation of drive identification through LED blinking, alarm management, hot spare disk designations and data scrubbing RAID from within the operating system without having to reboot into card BIOS. For example, this was the approach taken by OpenBSD in 2005 with its bio(4) pseudo-device driver and the bioctl utility, which provide volume status, and allow LED/alarm/hotspare control, as well as the sensors (including the drive sensor) for health monitoring;[7] this approach has subsequently been adopted and extended by NetBSD in 2007 as well.[8]
3 Array pairs were disabled successfully and we cant disable the last one with error "Unable to remove array pair 'STORAGE1' - 'STORAGE2'. Array pair is in use by one or more protection groups. Operation ID: 8b057fd2-7d60-4a1f-b844-949a0d58bd9b"
Use the Add/Discover feature to find and add the storage arrays you want to manage in the Storage plugin for vCenter. From the Manage page, you can also rename, remove, and provide new passwords for these discovered arrays.
For the plugin to display and manage storage resources, you must discover the storage arrays you want to manage in your organization's network. You can discover and then add a single array or multiple arrays.
If you choose to discover multiple arrays, you enter a network IP address range and then the system attempts individual connections to each IP address in that range. Any storage array successfully reached appears in the plugin and you can then add them to your management domain.
31c5a71286