Ive got a readynas 104 with 3, 4tb HDDs.. but my available storage is only 8tb .. i have a feeling its beause of raid 5... any way to change this to access the remaining 4tb?
You are correct it is because of RAID5, the 4TB disk space is being used as protection for your data in the event of one disk failure you will still be able to have access on your data. If you want to use it it as space for your data then you will have to change the RAID type you have. You can setup JBOD (Just a bunch of disks) which creates one volume per disk or use RAID0 which distributes data across multiple disks, resulting in improved disk performance. This RAID types though does not offer any protection to your data so any disk failure will result in data loss.
You will have to change from X-RAID to Flex-RAID first then destroy your current volume and create a new one.
Ive got a readynas 104 with 3, 4tb HDDs.. but my available storage is only 8tb .. i have a feeling its beause of raid 5... any way to change this to access the remaining 4tb?
The capacity rule for XRAID is "sum the disks and subtract the largest", which yields 9 TB (or ~8.2 TiB). The NAS actually displays TiB (1024*1024*1024*1024 bytes = 1 TiB).
This drop in capacity is needed in order to preserve your data if a disk fails, and it is also required if you want to expand the array in the future. The "missing" space holds the parity blocks that allow the NAS to regenerate the contents of any failed or missing disk from the remaining three.
To change the RAID mode, you need to change to flexraid, destroy the existing volume, and then create new volume(s) using RAID-0 or JBOD. This is destructive, so you'd need to restore all the data. After the change, a failed disk drive will result in data loss, so you'd need to restore the data from a backup. Also, you won't be able to expand storage without restoring data from backup.
There are two options if you decide to proceed. The one I recommend is to create four volume (one for each disk), and to spread your shares across them. That is a bit more work to maintain, but when a disk fails you will only lose the data on that disk. The other option is to create one volume that spans all four drives. That is somewhat more convenient, but when any disk fails you will lose all the data on the NAS.
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