User manual ZYXEL NSA-2400

[. . . ] NSA-2400 Network Storage Appliance User's Guide Version 1. 00 12/2006 Edition 2 www. zyxel. com About This User's Guide About This User's Guide Intended Audience This manual is intended for people who want to configure the Product Name [short] using the web configurator. You should have at least a basic knowledge of TCP/IP networking concepts and topology. Related Documentation · Quick Start Guide The Quick Start Guide is designed to help you get up and running right away. It contains information on setting up your network and configuring for Internet access. [. . . ] · Mirroring In a RAID system using mirroring, all data in the system is written simultaneously to two hard disks instead of one. This provides 100% data redundancy as if one disk fails the other has the duplicated data. · Duplexing Like in mirroring, all data is duplicated onto two distinct physical hard drives but in addition it also duplicates the hardware that controls the two hard drives (one of the drives would be connected to one adapter and the other to a second adapter). · Striping Striping is the breaking up of data and storing different data pieces on each of the drives in an array. This allows faster reading and writing as it can be done simultaneously across disks. Byte-level striping means that the first byte of the file is sent to the first drive, then the second to the second drive, and so on. Block-level striping means that each file is split into blocks of a certain size and those are distributed to the various drives. The size of the blocks used is also called the stripe size (or block size). · Parity 100 NSA-2400 User's Guide Chapter 7 Storage Screens In mirroring 50% of the drives in the array are reserved for duplicate data. Parity is another way to allow data recovery in the event of disk failure using calculations rather than duplicating the data. If you have `n' pieces of data, parity computes an extra piece of data. If you lose any one of the `n+1' pieces of data, you can recreate it from the `n' that remain, regardless of which piece is lost. Parity protection is used with striping, and the "n" pieces of data are typically the blocks or bytes distributed across the drives in the array. The parity information can either be stored on a separate, dedicated drive, or be mixed with the data across all the drives in the array. In the following figures, A1, A2, A3 and so on are blocks of data from the A file. Similarly, B1, B2, B3 and C1, C2, C3 ar blocks of data from the B and C files. 7. 4. 1 JBOD JBOD allows you to combine multiple physical disk drives into a single virtual one, so they appear as a single large disk. JBOD can be used to turn several different-sized drives into one big drive. For example, JBOD could convert 5 GB, 10 GB, 15 GB, and 20 GB drives into one large logical drive of 50 GB. Moreover, since data isn't striped across disks, if one disk fails, you should just lose the data on that disk (but you may lose data in the whole volume depending on the nature of the disk failure). You can add disks to the JBOD volume later (using the Add disk to JBOD feature) and even remove them so JBOD offers a lot of flexibility. However JBOD read performance is not as good as RAID as only one disk can be read at a time and they must be read sequentially. Data is not written across disks but written sequentially to each disk until it's full. Table 38 JBOD A1 A2 A3 A4 B1 B2 B3 B4 C1 C2 C3 C4 DISK 1 DISK 2 DISK 3 NSA-2400 User's Guide 101 Chapter 7 Storage Screens 7. 4. 2 RAID 0 RAID 0 spreads data evenly across two or more disks (data striping) with no mirroring nor parity for data redundancy, so if one disk fails the entire volume will be lost. Data can be written and read across disks simultaneously for faster performance. Table 39 RAID 0 A1 A3 A5 A7 A2 A4 A6 A8 DISK 1 DISK 2 RAID 0 capacity is the size of the smallest disk multiplied by the number of disks you have configured at RAID 0 on the NSA. [. . . ] · This device must accept any interference received, including interference that may cause undesired operations. This device has been tested and found to comply with the limits for a Class B digital device pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This device generates, uses, and can radiate radio frequency energy, and if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. [. . . ]