Linksys NSS2000 Cisco NSS4000 and NSS6000 Series Network Storage System Admini - Page 183

Glossary of Storage-related Terms and Acronyms D IEEE 802.1X: Standard for port-based network access control that authenticates devices attached to a LAN port. This standard establishes connection to a network and its connected resources if authentication is approved, and conversely, prevents access to the network if authentication fails. An authentication server resides in each Cisco Small Business NSS product. J JBOD: Just a Bunch of Disks. Multiple hard disk drives (HDDs) that are combined into a single virtual drive. In a JBOD configured array, each drive can be a different size or capacity (this storage method can be used to turn two or more odd-sized hard drives into one useful drive). There is no redundancy provided with a JBOD and the failure of one disk in the array usually results in the loss of the data stored on the JBOD. Journaling Filesystem: A fault-resilient filesystem that provides data integrity because updates to directories and bitmaps are constantly written to a serial log on disk before the original disk log is updated. If the system fails, a full journaling filesystem restores the data on the disk to its pre-crash configuration. It also recovers unsaved data and stores it in the location where it would have gone if the computer had not crashed. This type of system is beneficial for mission-critical systems. A physical journal logs verbatim copies of blocks that will be written later (for example, ext3) as compared with a logical journal that logs metadata changes in a special, more compact format. Logical journals can improve performance by reducing the amount of data that needs to be read from and written to the journal in large, metadata-heavy operations (for example, deleting a large directory tree). XFS keeps a logical journal. L LCD: Stands for Liquid Crystal Display and is a display technology that uses liquid crystals that flow like liquid and bend light. The LCD appears on the front of the NSS3000 chassis and can be used to determine various status details about the NSS3000. LDAP (Lightweight Directory Access Protocol): A protocol that lets users find organizations, workgroups, other users, network resources (such as directories, volumes, files) or peripheral devices (such as printers and NAS devices) on a local network, in a intranet or on the Internet without knowing the specific domain where they reside. A single LDAP directory can be mirrored on multiple servers that can be periodically synchronized. Linksys Small Business NSS4000 and NSS6000 Series Network Storage System Administration Guide 175