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BP1028 EqualLogic iSCSI for Fibre Channel Professionals 10
With EqualLogic PS Series storage each array contains a number of disks that are usually of the same
type – one exception being “hybrid” arrays which contain a mix of SAS and SSD disks. When an array is
added to a pool, all of the disks in that array are consumed and automatically added to the pool as
available space. When a RAID policy is assigned, it is assigned to all disks in that array (enclosure)
except for those automatically designated as hot spares. The pool is sub-divided into “pages” and
when volumes are created, a number of pages are allocated or reserved for that volume until the
capacity is met. A pool may contain up to 8 members (arrays) which may all be configured for the
same RAID level, or the pool may contain multiple RAID levels. A group may contain up to 16 arrays
total.
Note: A minimum of two arrays are required in a pool to allow for multiple RAID levels to be used in
the pool.
Figure 5 - How EqualLogic storage is virtualized
While many storage administrators may be accustomed to determining exact placement of volumes
on physical disks (through the use of RAID groups or sets), the virtualized architecture of EqualLogic
PS Series arrays can offer advantages over other designs. In the case where a pool contains multiple
RAID policies, automatic tiering of data will occur over time, placing more frequently accessed data on
faster disks and/or RAID types. When an additional array is added to a pool, volumes may
automatically redistribute across multiple members, which can lead to higher performance.
Administrators can also easily migrate volumes from one pool to another without downtime.