ZyXEL NSA-220 Plus User Guide - Page 120

Chapter 5 Storage 5.6 Storage Technical Reference This section provides some background information about the topics covered in this chapter. 5.6.1 Volumes and RAID A volume is a storage area on a disk or disks. You can create volumes on the internal disks and external disks attached to the USB port(s). You can spread a volume across internal disks but not between internal and external disks. RAID (Redundant Array of Independent Disks) or JBOD is the storage method that the NSA uses. The storage method you use depends on how many disks you have and how many volumes you want to create. It's important that you consider this carefully as all data is deleted when you re-create a volume. Note: Back up your data before deleting or re-creating a volume! For example if you originally have one disk configured as JBOD, and you then install another disk and want to configure the two disks to use RAID 1, you should first back up all your data on the two disks (see the Memeo Autobackup utility on the included CD) and then restore your data later after you create the new volume type. Below is a table that summarizes some attributes of the various RAID levels as supported on the NSA. For capacity and storage efficiency, "S" is the size of the smallest drive in the array, and "N" is the number of drives in the array. Storage efficiency assumes all drives are of identical size. Performance rankings are approximations. Table 20 RAID Quick Comparison RAID Level 0 Number of Disks 2 Capacity S*N Storage Efficiency 100% Fault Tolerance None Availability Y Read Performance YYYY Write Performance YYYY 1 2 S*N/2 50% YYYY YYYY YYY YYY 120 NSA-220 Plus User's Guide