Dell EqualLogic PS6210XS EqualLogic Group Manager Administrator s Guide PS Ser - Page 34

2 Architecture Fundamentals The Dell EqualLogic product family provides a unified file and block storage platform. Block-level storage consists of a sequence of bytes and bits of a certain length, called a block. Each block stores the data (like a hard drive) and the disk controller reads and writes data to the disks inside the storage array. Block-level access enables storage administrators to stipulate which block to send reads and writes to for the best performance. In file-level storage, the operating system keeps track of data in a directory of file and folder names. Access to data by an application is by file name and location within the file, and then translated into block-level access for physical reading and writing of data. Block-level transfers in a SAN are typically faster than file-level transfers in a NAS because they do not have any file system or network overhead. The PS Series SAN provides block-level access to storage data through direct iSCSI access to PS Series arrays. The FS Series NAS appliance provides file-level access to storage data using NFS (UNIX) or SMB (Windows) protocols and the Dell FluidFS file system. This architecture uses a scale-out design, which enables you to increase performance as you add capacity, because the software manages the workload of data writes and the subsequent data reads across all the resources in the storage infrastructure. PS Series Architecture The PS Series architecture comprises three fundamental components: the PS Series array, the PS Series group, and the PS Series storage pool. These components coordinate operations and work together to form a virtual storage system. The foundation of the PS Series architecture is a PS Series array. Each array is composed of redundant components: disks, controllers with mirrored write-back caches, network interfaces, power supplies, and cooling fans. When you configure a PS Series array, you add it to a PS Series group. A group can consist of up to 16 arrays of any family or model, as long as all arrays in the group are running firmware with the same major and minor release number. The group appears to the client servers as a single entity that offers network storage access in block mode. NOTE: Dell recommends that all arrays run the same version of PS Series firmware at all times, except during the firmware update process. Each array in a group is called a group member. You add members to the group, and allocate storage space in the group by creating storage pools. A pool can have from one to eight members, and you can create up to four pools in a group. Each member contributes its resources to the pool (disk space, processing power, and network bandwidth). As you add or remove members, the pool of storage space grows or shrinks. Hardware and other details remain hidden. By default, a group member's RAID-protected disk space is added to the default storage pool. When you add a new member, it is automatically assigned to the default pool. The default pool cannot be deleted; however, you can create additional pools as required for your environment. You can assign members to the pools at any time. The PS Series array software load balances data and network I/O to the group across all the group members' resources. When a group contains more than one member, those members might have different capacity levels and use different RAID levels. The load balancers transparently maintain optimal system performance and eliminate downtime to servers, applications, and users. Next, you create volumes and assign them to the appropriate pool. (You can also organize volumes into folders for easy reference.) A volume provides the structure for the group. You can create a volume on a single group member or one that spans multiple group members. You identify a volume by specifying a unique volume name. Hosts on the network see these volumes as iSCSI targets. You set access controls for each volume so that only computers with an iSCSI initiator and the correct access credentials can access volume data. 34 Architecture Fundamentals