LaCie ICA-312 User Manual page 173

LaCie SimplyRAID
RAID configurations will use equal disk capacties among the pool of hard drives to protect data. Rather then lose
hard disk capacity overhead in mixed disk environments, SimplyRAID will preserve the extra space to use when
new disks are added to the enclosure. Unlike standard RAID models, you can easily expand the array without
losing data. For example, two 1TB disks will create a RAID 1 array without any disk capacity overhead. However,
one 1TB disk paired with one 2TB disk can only create 1TB of protection since data cannot surpass the storage
capacity of the smallest disk. SimplyRAID will calculate the overhead and prepare it for future disk expansion.
RAID 0
RAID 0 (also called Spanning mode in some LaCie devices), is the fastest RAID mode. In a RAID 0 array, the
available capacities of each disk are added together so that one logical volume mounts on the computer. It
offers the best performance but no protection in the case that a disk fails.
Caution: In a RAID 0 array, if one physical disk in the array fails, the data of all disks becomes inaccessible
because parts of the data have been written to all disks.
RAID 1
RAID 1 is a secure RAID mode that is available if the LaCie 5big NAS Pro has only two disks installed. RAID 1
provides data safety since all data is written to each disk at the same time. In the event of a single disk failure,
data remains available on the other disk. Due to the time it takes to write the data twice, performance is slightly
reduced. RAID 1 is a good choice when safety is more important than speed. However, RAID 1 also reduces the
available disk space by 50% due to the need to write each bit of data on each hard drive.
RAID 5
In RAID 5, data is striped across all disks (minimum of three) and a parity block for each data block (P in the
illustration below) is written on the same stripe. If one physical disk fails, the data from the failed disk can be
rebuilt onto a replacement disk. No data is lost in the case of a single disk failure, but if a second disk fails
before data can be rebuilt to a replacement hard drive, all data in the array will be lost.
LaCie 2big NAS (OS 3.0) | LaCie 5big NAS Pro User Manual 173