Electrical computers and digital processing systems: memory – Storage accessing and control – Specific memory composition
Reexamination Certificate
1999-06-11
2003-02-11
Kim, Matthew (Department: 2186)
Electrical computers and digital processing systems: memory
Storage accessing and control
Specific memory composition
C711S150000, C711S170000
Reexamination Certificate
active
06519679
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to storage devices for computer systems, and particularly the configuration of storage devices for computer systems.
2. Description of the Related Art
Computer systems generally, and servers in particular use a variety of magnetic, optical, and solid state storage devices in order to provide, process, and store data and applications software. In most user environments, it is very important for the storage devices to have high capacity, high performance, high reliability, and the ability to easily add storage. Since the primary storage device used by most computer systems is the hard disk drive, a great deal of effort has been expended in developing hard drive storage systems that possess all of the aforementioned attributes.
In general, a drive array is a collection of hard disk drives grouped together to create an array of physical drives. Drive array technology, typically in the form of a dedicated hardware controller, or controller software executing on a computer system's host processor, distributes data across one or more disk drives to combine these physical drives into one or more logical drives, which possess certain advantages (e.g., performance, reliability, capacity). Distributing the data across multiple disk drives makes it possible to access data concurrently from multiple drives in the array, yielding data transfer rates faster than non-arrayed drives. This technique for allowing a collection of drives to appear (and in some sense behave) as a single virtual disk or logical volume is often referred to as disk striping, or simply striping. The storage capacity of a striped array of disks is the sum of the capacities of the individual drives making up the array, less any space required for management of the array. An array using striping alone has at least one serious disadvantage, the failure of any one drive in the array leads to the failure of the entire volume.
For hard disk drives, and in some instances other magnetic and optical storage media, one of the more popular storage device systems to be developed in the last decade is the redundant array of inexpensive disks (RAID, sometimes described as a redundant array of independent disks). RAID systems use redundant information, stored on one or more drives to allow the array to survive the failure of one or more drives in the array. RAID storage technology provides several fault tolerance options, designated by a RAID level number, to protect data. It should be noted that the RAID level chosen, and thus the RAID configuration implemented, affects the performance, capacity, expandability, and cost of the storage system.
There are at least six common RAID levels (
0
-
5
). RAID Level
0
is, in essence, striping as previously described. Consequently, it is not redundant, and does not truly fit the “RAID” acronym. Since no redundant information is stored, performance is very good, but the failure of any disk in the array results in data loss. RAID Level
1
provides redundancy by duplicating all data from one drive on another drive, also referred to as mirroring. The performance of a level
1
array is only slightly better than a single drive, but if either drive fails, no data is lost. This is a good entry-level redundant system, since only two drives are required; however, since one drive is used to store a duplicate of the data, the cost per megabyte is high. RAID Level
2
, which uses Hamming error correction codes, is intended for use with drives which do not have built-in error detection. All SCSI drives support built-in error detection, so this level is of little use when using SCSI drives. RAID Level
3
stripes data at a byte level across several drives, with parity information stored on one drive. It is otherwise similar to level
4
. Byte-level striping requires hardware support for efficient use. RAID Level
4
stripes data at a block level across several drives, with parity information stored on one drive. The parity information allows recovery from the failure of any single drive. The performance of a level
4
array is very good for reads (the same as level
0
). Writes, however, require that parity data be updated each time. This slows small random writes, in particular, though large writes or sequential writes are fairly fast. Because only one drive in the array stores redundant data, the cost per megabyte of a level
4
array can be fairly low. Finally, RAID Level
5
is similar to level
4
, but distributes parity information among the drives. This can speed small writes in multiprocessing systems, since the parity disk does not become a bottleneck. Because parity data must be skipped on each drive during reads, however, the performance for reads tends to be considerably lower than a level
4
array. The cost per megabyte is the same as for level
4
.
From this simple description of the various RAID levels, it can be seen that selection of a particular RAID level depends not only on the general properties desired by a user, but by the hardware resources available, and the user environment (e.g. type of server) in which the array is used. For example, RAID
0
might be desirable where the user is processing large, but temporary files because of that level's speed, and the application's relatively low need for failure protection. RAID
0
would not be the best choice for a database server precisely because there is no built-in failure protection.
Thus, it should be readily recognized by those having ordinary skill in the art that the process of selecting an appropriate RAID level for a particular application and implementing that level as a configuration of a storage device can be complex, requiring information about desired performance, available resources, and application details. Prior art storage management tools used for configuring and managing storage systems require users to have a great deal of knowledge about RAID technology, applications to be used in conjunction with a RAID implementation, and resources available. Accordingly, it is desirable to have an application based storage configuration solution to assist users with configuring and managing storage devices, particularly RAID devices.
SUMMARY OF THE INVENTION
It has been discovered that a storage device configuration manager implemented in software for a computer system including a processor, a memory coupled to the processor, and at least one storage device coupled to the processor, can advantageously allow a user having relatively limited knowledge to configure storage devices for use with specific applications. The storage device configuration manager includes a user interface allowing for selecting, editing, deleting, and/or activating storage polices. The storage policies include information useful for configuring the storage device to operate efficiently with a particular application, or within a particular user environment. The information is used by a policy engine to configure the storage device, thereby reducing the knowledge and effort required by a user. Additionally, the storage device configuration manager can provide a common interface for configuring a number of different RAID devices, even devices made by different manufacturers. Another advantage to the storage device configuration manager is that it provides a computer system manufacturer, vendor, or service organization a convenient mechanism for disseminating its expertise and experience associated with specific storage/application combinations.
Accordingly, one aspect of the present invention provides a storage device configuration manager for a computer system that includes a processor, a memory coupled to the processor, and at least one storage device coupled to the processor. At least a portion of the storage device configuration manager is software executable on the processor. The storage device configuration manager includes a user interface and a policy engine. The user interface is operable to allow a user to perform at least one of: creating a storage policy,
Chen Xu
Devireddy Narayan
Dell USA L.P.
Hamilton & Terrile LLP
Holland Robert W.
Kim Matthew
Peugh B. R.
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