Disk Array Storage terminology

SCSI

Small Computer System Interface (Small Computer System Interface), which was first developed at 1979, is an interface technology developed for minicomputers. However, with the development of computer technology, now it is completely transplanted to a normal PC.

ATA (at embedded interface)

The purpose of this interface is to directly connect the bus in the at computer manufactured in 1984 with the driver and controller that are combined. The "at" in Ata comes from the at computer that used the ISA bus for the first time.

ATA started from the earliest ATA-1, has experienced development history from ATA-1, ATA-2, ATA-3, ultra ata, ultra ATA/33, ultra ATA/66, ultra ATA/100, ultra ATA/133.

Serial ATA)

The serial data transmission mode is used. Only one bit of data is transmitted in each clock cycle. ATA Hard Disks always adopt parallel transmission mode, and signals between lines interfere with each other. during high-speed data transmission, the system stability is affected. Since the serial transmission mode does not encounter Signal Crosstalk problems, to increase the transmission speed, you only need to increase the working frequency. Serial ATA only requires a 4-wire cable.

SATA adopts a point-to-point transmission mode, so that you do not need to set a Master/Slave disk for the hard disk when using the SATA hard disk. Instead, each hard disk is directly connected to the system through a data channel. According to the sata1.0 standard, the interface transmission rate of the hard disk is 150 Mb/s, Sata can be expanded to 2X and 4x specifications, and the corresponding transmission rate is increased to 300 MB/S and 600 Mb/s respectively. SATA hard disks can also achieve hot swapping, but no operating system has yet to support this feature. People will not be able to enjoy the convenience of this feature Until Microsoft's next-generation operating system Windows longhorn is available.

Network attached storage (NAS)

Connect a storage device to a group of computers through a standard network topology (such as Ethernet. NAS is a component-level storage method, which focuses on helping working groups and department-level organizations quickly increase storage capacity.

Das (Direct Attached Storage-Direct Attached Storage)

A storage device is directly connected to a computer through a SCSI interface or fiber channel. Das products include storage devices and integrated simple servers, which can be used to implement all functions related to file access and management.

San (Storage Area Network-Storage Area Network)

Connect to a group of computers through fiber channel. Multi-host connection is provided in the network, but not through the standard network topology. San focuses on the unique problems of enterprise-level storage and is mainly used in a work environment with large storage capacity.

Array: Array

The disk array mode integrates the storage space of several disks to form a large, single, continuous storage space. The RAID Controller uses its SCSI channel to combine multiple disks into a disk array. Simply put, an array is a disk system composed of multiple disks that work in parallel. Note that hot backup disks cannot be added to the array.

Array spanning: array spanning

An array overlay is a process of re-integrating the storage space in two, three, or four disk arrays to form a logical drive with a single continuous storage space. The raid controller can span several consecutive arrays, but each array must consist of the same number of disks, and these arrays must have the same raid level. That is to say, the spanning array is a combination of several already formed arrays. Raid 1, RAID 3, and RAID 5 form raid 10 after they are crossed, raid 30 and raid 50.

Cache Policy: high-speed cache policy

The RAID Controller has two high-speed cache policies: cached I/O (Cache I/O) and direct I/O (direct I/O ). Cache I/O always adopts read and write policies, and is often cached randomly during read operations. Direct I/O always reads new data directly from the disk. If a data unit is read repeatedly, a moderate read policy is selected, and the read data will be cached. Data enters the cache only when the read data is accessed repeatedly, but no data enters the cache in the completely random read state.

Capacity Expansion: Capacity Expansion

In the RAID Controller's quick Configuration tool, when the virtual capacity option is set to available, the Controller will create a virtual disk space, and then the volume can expand the added physical disk to the virtual space through restructuring. Refactoring can only be performed on a single logical drive in a single array. You cannot use online resizing across arrays.

Channel: Channel

The electrical path that transmits data and control information between two disk controllers.

Format: Format

In the process of writing zero to all data areas of a physical drive (hard disk), formatting is a pure physical operation. At the same time, it checks the consistency of the hard disk media, and mark the unreadable and bad sectors. Most hard disks have been formatted at the factory, so they must be formatted only when an error occurs in the hard disk media.

Hot spare: Hot Standby

When a disk in use fails, a idle, powered, and standby disk will replace the faulty disk immediately. This method is hot backup. The hot backup disk does not store any user data. It can have up to 8 disks as hot backup disks. A hot backup disk can belong to a single Redundant Array or be part of the hot backup disk pool of the entire array. In a specific array, there can be only one hot backup disk.

When a disk fails, the Controller's firmware can automatically replace the faulty disk with a hot backup disk, and re-build the data originally stored on the faulty disk to the hot backup disk using algorithms. Data can only be rebuilt from a redundant logical drive (except RAID 0), and the hot backup disk must have enough capacity. The system administrator can change the faulty disk and specify the new hot backup disk as the new one.

Hot Swap disk module: Hot Swap disk Mode

The Hot Swap mode allows the system administrator to change the faulty disk drive when the server is continuously powered and network services are not suspended. Since all power supplies and cable connections are integrated on the server's baseboard, Hot Swap mode can directly remove the disk from the drive cage slot, which is very easy to operate. Then insert the replaced Hot Swap disk into the slot. Hot Swap Technology works only when RAID 1, 3, 5, 10, 30, and 50 are configured.

I2o (Intelligent Input/Output): Intelligent Input and Output

Intelligent Input/output is an industrial standard. The architecture of the input/output subsystem is completely independent of the network operating system and does not require the support of external devices. Drivers used by i2o can be divided into the operating system Services Module (osms) and hardware driver module (hdms ).

Initialization: initialization

Writes zero to the data area of the logical drive, and generates the corresponding parity to make the logical drive ready. Initialization will delete the previous data and generate parity. Therefore, the logical drive will perform consistency detection during this process. An array that has not been initialized cannot be used, because no parity zone is generated, the array will produce a consistency check error.

IOP (I/O processor): Input/Output Processor

The input and output processor is the command center of the raid controller, which includes command processing, PCI and SCSI bus data transmission, raid processing, and disk drive reconstruction, high-speed cache management, error recovery, and other functions.

Logical drive: logical drive

Virtual Drive in the array, which can occupy more than one physical disk. A logical drive splits an array or a disk that spans an array into contiguous buckets distributed across all disks in the array. The raid controller can set up to eight logical drives of different capacities, and at least one logical drive must be set in each array. The input and output operations can only be performed when the logical drive is online.

Logical volume: logical volume

A Virtual Disk formed by a Logical Disk is also called a disk partition.

Mirroring ing: Image

A type of redundancy. An identical copy of data on one disk exists on another disk, that is, an image. Raid 1 and raid 10 use images. Parity: parity bit

In data storage and transmission, an additional bit is added to the byte to verify errors. It usually generates a redundant data from two or more original data, and redundant data can be reconstructed from one original data. However, the parity data is not completely copied to the original data.

In raid, this method can be applied to all disk drives in the array. The parity bit can also form a dedicated parity method. In the dedicated parity, the parity data can be distributed across all the disks in the system. If a disk fails, you can use the data on other disks and the parity data to reconstruct the data on the faulty disk.

Snapshot: Snapshot

Snapshot is a backup technology of a static image (frozen image). It is a technology that retains the image of a file system at a certain time point, at its core, the backup and recovery processes are copied in real time (point-in-time. Snapshot can quickly generate multiple snapshots of the current data. These snapshots can be used for data backup, data analysis, data recovery, and other program data. Compared with backup software systems and image software systems, it has its own characteristics: for example, you can avoid the problem that services cannot be provided for a long time when backing up large data volumes, and achieve real-time data recovery, real-time data analysis and other special functions.

Power fail safeguard: power-down protection

When this item is set to available, all data will be stored on the disk during the rebuild process (not rebuild) until the rebuild is complete. In this way, if a power loss occurs during the reconstruction process, there will be no risk of data loss.