Module 2-1. Hardware PDF

**Module 2-1. Hardware** OBJECTIVE 1a. Identify relationship of basic facts and state general principles of server hardware storage types. \- Storage Types/Connections \- Configure System Storage **STORAGE TYPES/CONNECTIONS** It\'s important to understand your server\'s hardware from the grou...

**Module 2-1. Hardware** OBJECTIVE 1a. Identify relationship of basic facts and state general principles of server hardware storage types. \- Storage Types/Connections \- Configure System Storage **STORAGE TYPES/CONNECTIONS** It\'s important to understand your server\'s hardware from the ground up. Today\'s server hardware is sophisticated and specialized to support multiple users, applications and processors, as well as provide fault tolerant, highly available services. There are various server components such as CPU, RAM, bus types, bus channels, and expansion slots, as well as NICs and hard drives. **SERIAL ADVANCED TECHNOLOGY ATTACHMENT (SATA)** SATA is a hard drive interface providing faster transfer times, thinner more flexible cabling, and easier plug-and-play connections. It creates a point to point connection between the SATA device and the SATA controller's host adapter meaning each drive connects to one port (no more daisy-chaining) and each hard drive operates on its own independent SATA channel. It transfers data in serial bursts instead of parallel. This allows the single stream of data to move faster than the multiple streams of data transmitting from parallel devices. Many motherboards are now available supporting up to ten SATA drives. If additional storage is required, more host adapters/controllers may be added. **NETWORK ATTACHED STORAGE (NAS)** Network-Attached Storage (NAS) and Storage-Area Networks (SANs) are commonly used today to provide data storage that is not directly attached to the servers. They incorporate a pool of array storage drives accessed by, yet independent, of servers. NAS and SAN differ depending on the network structure servers and data storage use to connect to each other. We will look at each storage device and identify the difference of each. The NAS is a specialized storage device or group of storage devices providing centralized fault- tolerant data storage for a network. NAS differs from RAID in it maintains its own interface to the LAN rather than relying on a server to connect it to the network and control its functions. Think of NAS as a unique type of server dedicated to data sharing. A NAS device resides on the Local Area Network (LAN) as an independent network node and has its own IP address. An important benefit of NAS is its ability to provide multiple clients on the network with access to the same files. When using NAS, the client requests a file from its usual file server over the LAN. The server then requests the file from the NAS device on the network. In response, the NAS device retrieves the file and sends it to the server. In-turn, the server then re-transmits it to the requesting client. NAS is appropriate for organizations requiring not only fault-tolerance but also fast data access. **STORAGE AREA NETWORK (SAN)** A SAN is a specialized high-speed network of storage devices and switches connected to servers or computer systems. It presents a shared pool of storage devices to multiple servers. They support centralized storage management making it possible to move data between various storage devices, share data between multiple servers, as well as backup and restore data more efficiently. If one storage device within a SAN suffers a fault, data is automatically retrieved from elsewhere in the SAN. Not only are SANs extremely fault-tolerant but they are also extremely fast. Much of their speed can be attributed to the use of fiber-optic media (in some cases copper) and in conjunction with proprietary protocols. One popular SAN transmission method is called Fibre Channel. A Fibre channel connects devices within the SAN and also connects the SAN to other networks. Because it depends on Fibre Channel, the SAN is not limited to the speed of the client/server network it is providing data storage for. In addition, because the SAN does not belong to the client/server network, it does not have to contend with the normal overhead of the network. A SAN frees the client/server network from the traffic intensive duties of backing up and restoring data. Another advantage to using a SAN is it can be installed on a location separate from the LAN it serves. Being in a separate location provides added fault tolerance. Like the NAS, a SAN provides the benefit of being highly scalable. After establishing a SAN, further storage and new devices to the SAN can be easily added without disrupting client/server activity on the network. Finally, SANs use a faster more efficient method of writing data than either NAS devices or a typical client/server network. Due to their very high fault-tolerance, massive storage capabilities, and speedy data access; SANs are best suited to environments with huge quantities of data that must always be quickly available. Usually such an environment belongs to a very large enterprise. A SAN is typically used to house multiple databases (inventory, sales, payroll, employee records, etc.). **CONFIGURE SYSTEM STORAGE** **REDUNDANT ARRAY OF INDEPENDENT DISKS (RAID)** RAID technology has been around for approximately 20 years and a number of factors have come together to make RAID a reality for both large servers as well as desktop systems. It not only has increased our capabilities to store and retrieve data, but also to limit data loss caused by hardware failure (i.e. fault tolerance). Once deciding to implement RAID technology onto the server or network, considerations must be made as to their types and configuration. One solution needing deliberation is whether to implement a hardware or software solution. **RAID TYPES** **Hardware RAID** Includes a set of disks and a separate disk controller. The hardware RAID array is managed exclusively by the RAID disk controller attached to a server through the server's controller interface. This will appear as another storage device to the operating system. **Software RAID** Relies on software to implement and control RAID techniques over virtually any type of hard disk. It is less expensive overall than hardware RAID because it does not require a special controller or disk array hardware. **RAID LEVELS** There are different RAID levels describing different methods of providing data redundancy or enhancing the speed of data throughput to and from groups of hard drives. There are literally thousands of methods used to set up RAID. It will depend largely on the level of RAID desired, the operating system, and how much money you are willing to spend. **RAID 0: Disk Striping (Block-by-Block)** RAID 0 offers striping (meaning data is "split" evenly across two or more disks) with no parity or mirroring. The data is written to the physical hard disk block-by-block. The data is broken down into stripes or chunks of data with a particular size defined by the user. These stripes are then written one-by-one to different disk drives or arrays. All the stripes are not written to the same drive rather they are striped (written) across the different drives in a sequential manner. RAID 0 increases the performance of the hard disks. The RAID controller sends the first block to the first hard disk. This takes some time to write the block. While the first block is being written to the disk, the RAID controller is already sending the second block to the second disk and Block 3 to the third hard disk and so on. RAID 0 is the simplest RAID level and is the easiest to implement. As the data is divided into equally-sized stripes, it can be easily written onto the disk drives. Searching for a chunk of data is also speedy. The search is carried out in parallel (i.e. one level on each disk drive is searched for the chunk of data). As the data chunks are divided on a number of disk drives, the seek time is reduced to exactly half the amount of time it takes to search a single large disk. Although RAID 0 increases the performance of the hard drives, it is not fault-tolerant. If a physical hard disk is lost or crashes, all the data on the disk becomes unrecoverable or lost. **RAID 1: Disk Mirroring/Duplexing (Block-by-Block)** When data availability is of great importance (i.e. in case a disk fails or data is lost and there is a chance to recover it through a backup), the recommended form of storage is RAID Level 1. This form of RAID carries out mirroring or duplexing (replicating) wherein the data present on a disk is copied onto one disk or a pair of disks. Thus, for each disk drive there exists a mirror having a complete and identical copy of the original data. With RAID 1, fault-tolerance is a primary concern. The basic form of RAID Level 1 brings together two physical hard disks to form one virtual hard disk by mirroring the data. If the server writes a block to the virtual hard disk, the RAID controller writes this block to both physical hard disks. The individual copies are also called mirrors. Normally two or three copies of the data are kept (three-way mirror). In a normal operation with pure RAID 1, performance increases are only seen for read operations. After all, when reading the data the load can be divided between the two disks. However this gain is low in comparison to RAID 0. When writing with RAID 1, a reduction in performance is seen since the RAID controller has to send the data to both hard disk. **RAID 5: Disk Striping with Distributed Parity (Block-Level)** This is perhaps the most popular data storage technique in use today. In RAID 5, both data and parity information are striped across three or more drives. It is similar to RAID 4 except it exchanges the dedicated parity drive for a distributed parity algorithm; writing data and parity blocks across all the drives in the array. This removes the "bottleneck" the dedicated parity drive represents. RAID 5 has high read/write speeds allowing multiple writes. Its capacity is very good as well by being very cost-effective. A disadvantage is it is not very efficient with large data transfers. **RAID 6: Disk Striping with Dual Distributed Parity (Block-Level)** RAID 6 is an extension of RAID 5. Two parity blocks are written in this level to help in the data recovery process. It was used for preventing data loss in case of concurrent disk failures. Its advantages are the performance is high for read operations and it is good to use for large data transfers. The disadvantage is the performance is not very good for small data transfers. When writing data it requires a larger amount of time due to the fact two parity blocks are created. **RAID 0+1/1+0/RAID 10: Striping and Mirroring Combined** After these RAID levels were defined, some manufacturers designed ways to combine the different RAID Levels. For example: what if you took two pairs of striped drives and mirrored the pair? You would get what is called RAID 0 + 1. If you took two pairs of mirrored drives and striped the pairs? You then get what is called RAID 1+0 or what is often called RAID 10. Combinations of different types of single RAID are called multiple RAID or nested RAID solutions. Let's consider RAID 10. The problem with RAID 0 and RAID 1 is they increase either performance (RAID 0) or fault- tolerance (RAID 1). However, it would be nice to have both performance and fault-tolerance. This is where RAID 0+1/1+0 and RAID 10 come into play. These RAID levels combine the idea of RAID 0 and RAID 1. RAID 0+1 and RAID 10 each represent a two-stage virtualization hierarchy. A minimum of four physical hard disks are used in RAID 10. The RAID controller initially brings together each four physical hard disks to form a total of two virtual hard disks only visible within the RAID controller by means of RAID 0 (striping). In the second level, it consolidates these two virtual hard disks into a single virtual hard disk by means of RAID 1 (mirroring); only this virtual hard disk is visible to the server. This hard disk is larger, faster and more fault-tolerant than one physical hard disk.