The capacity of the qNAS servers is dependent upon several factors. The most obvious being the number and capacity of the drives that it uses. Beyond this you should consider the formatted capacity of the individual drives, the RAID (data security) level that you wish to use, and finally whether you wish to leave drives in the system as hot-spares to immediately replace drives should they fail.

A drives capacity is always less than that quoted by its model number. Disk manufacturers quote 1GB as 1000MB but operating systems use 1024MB per 1GB. This means that a drive quoted as 750MB will actually only provide around 690MB of useable storage.

All our systems utilise hardware RAID for data security. The level of protection is dependent upon the role of the server and the customers own requirements. We recommend that systems should incorporate a hot-spare drive to reduce the window of time that a system is operating in degraded mode in the event of a drive failure.

RAID 0
RAID0 (striped) provides the maximum storage capacity and speed at the expense of data security. In this configuration should a single drive fail all data on the system will be lost. We do not recommend this configuration for our servers.

RAID 1
RAID1 (mirror) provides data security by continuously backing up data from one drive to another. This configuration only works with two drives and provides the capacity of one. Not particularly suitable for use with our servers.

RAID 10
RAID10 halves the maximum capacity of available storage. Half of the drives are striped together into a single volume which is then mirrored to another stripe set. Only recommend for configurations up to 4 drives.

RAID 5
RAID5 writes data and parity across all drives. Parity data allows the system to re-create data lost in the event of a drive failure. Writing the parity data requires a processing overhead which reduces the speed in relation to RAID0. The capacity of the RAID is the total number of drives less one. It provides a good balance between performance and data security and will continue to operate in the event of a single drive failure.

RAID 6
RAID6 uses the same structure as RAID5 but writes the parity data to two drives at a time providing redundancy in the event of two drives failing. The performance overhead is greater than RAID5 and the capacity is reduced to the number of drives less two. However RAID6 does provide increased data security and is recommended for mission critical applications.

qNAS capacity when configured as RAID0

qNAS capacity when configured as RAID5

qNAS capacity when configured as RAID6