Storage Fundamentals-Architecture and RAID

1. Server and Storage System

Server: provides compute power and service for network requests.

Storage System: storage device + Storage Management System +raid Disk system, accept I/O requests.

Storage Architecture:

The DAS (direct Attach STorage) storage device is connected directly to the server with an interface of IDE or SCSI.

NAS (Network attached Storage) network-attached storage, which uses networking technology to connect storage systems (servers) via switches, and interfaces to TCP/IP.

SAN (Storage area Network) storage networks with FC (Fibre Channel), networked storage systems with FC (Fibre Channel) interfaces.

RAID: (Redundant array of independent Disks) disk array

2. Data storage Type

File storage: NAS

Block storage: Das and SAN

Object Storage (Networked storage architecture): OSD Device

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3. Storage architecture and features

The
• das is a server-centric storage structure that connects the storage device directly to the server (most SCSI interfaces), and then the server is connected to the network, and any client on the network that accesses a storage device must go through the server. Because the storage devices connected on each node server are independent, the storage devices on the entire network are scattered, independent, and cannot be shared. Das storage mode is server-centric, all traffic must be forwarded by the server, so the burden of the server is heavier, but also the bottleneck of the whole system. The CPU, memory, and I/O of the server affect the performance of the DAS. The
• NAS is a data-centric storage structure, a storage device that is completely disconnected from the server and directly connected to the Internet, and NAS directly connects the task-optimized storage device to the network, where users can share data from NAS devices directly over the network. addresses the storage-to-server dependencies and server bottlenecks in the DAS. Under the NAS, the client requests for resources are sent directly to the NAS device, and the data returned by the request is sent directly to the requestor without the server's transit, which greatly improves the response speed and transmission rate. NAS uses the RJ-45 standard network interface, as long as the NAS device is connected to a TCP/IP network via a hub or switch, assigning an IP address. NAS supports cross-platform file sharing in heterogeneous network environments, supports window/unix/apple and so on. The
• San is a network-centric storage structure that differs from ordinary Ethernet and is a high-performance network located at the server backend for connecting servers, disk arrays, and storage devices with libraries. The SAN is a data storage centric, with a scalable network topology, with direct connections to optical channels (or iSCSI) with high transfer rates, providing multiple selectable data exchanges between any node within the SAN, and centralizing data storage management within a relatively separate storage area network. The difference between sans and traditional das is that Das's storage devices specialize in the servers that are connected, while San mode allows all servers to share all storage devices through high-speed channels. The main devices of the San: storage devices (disk arrays), servers, connected devices (network switching devices and fiber optics, etc.), storage management software. The advantage of a SAN is that all storage devices are highly shared, and all storage devices can be centrally managed with redundant backup capabilities, and a single server outage system still works.

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Das is characterized by the storage of proprietary properties, each server being the" MANAGER "of its attached storage device, Exclusive and independent; Sans can meet high-demand storage requirements, but their fibre switch costs are too high, and there is a distance between servers and storage devices, and NAS is shared without the storage-device-specific problems of DAS, and there are no high-cost san fibre switch costs and distance constraints, However, its NAS server itself limits its performance, is not suitable for video storage, but is suitable for multi-point concurrent access scenarios, iSCSI has a SAN architecture and relatively low cost, but the configuration of the switch and network stability requirements are high

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4. RAID Basics

JBOD: A set of disks in the same disk cabinet, does not provide fault tolerance, raise the small, due to a jbod defect occurred raid.

Striped: Raid is a data stripe independent disk that classifies multiple drives into a single logical storage unit combination.

Levels: Each level has different cost, performance, and fault-tolerant benefits.

Raid:

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JBOD:

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RAID Level 0: Stripe set

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RAID Level 1: Mirroring

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RAID Level 3: Stripe set for a dedicated disk check

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RAID Level 5: Stripe set for distributed checksums

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RAID Level 10:

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RAID Level 30:

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RAID Level 50:

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RAID level comparison:

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RAID0: There is no checksum for parallel transmissions.

RAID1: The capacity utilization ratio is half, redundant quantity is big.

RAID3: Parallel transmission, special disk parity, suitable for big data.

RAID5: Parallel transmission, non-special disk parity, suitable for small data.

RAID10: half RAID1 half RAID0.

Storage Fundamentals-Architecture and RAID