I'm totally new to all this hard disks matter and even newer to topic with RAID.
I hope somebody can help me!
I have installed Ubuntu 14.04 LTS (BioLinux) on Dell Precision T7500, with Dell PERC 6/i Adapter RAID controller, but only 1.8TB usable.
I have 8 disks, totaling up to 12TB, how do I activate and use them all?
I created new Virtual disk and followed through the short guide from the below 2 links to install my BioLinux with USB stick.
http://www.orangecomputers.com/node/?command=kb&docid=25
https://www.youtube.com/watch?v=llvGKVYSQ4A
After successfully booting, gparted only showing 1.8TB size available and there is only 1MB of unallocated space.
How do I activate back the other disks and get the Ubuntu (BioLinux) run on total 12TB space (or at least 6TB)? Is it possible?
Something to tweak in the Configuration Utility? Use other levels of RAID?
And what is "HotSpare"??
Greatly appreciate any help from anyone :)
When you use RAID 1, the disks are all duplicates of each other. If you have the 12 disks, the data will be duplicated 12 times up to the capacity of the smallest disk.
What you want is either RAID 0, 5, 6, or 10.
In RAID 0, all the disks are used to store data with no redundancy. The total space would be the smallest disk size * 8.
In RAID 5, data is stored with parity bits. This allows a single disk to fail and data still be readable. The size of the virtual disk would be the size of the smallest disk * 7.
In RAID 6, it is basicly the same as RAID 5 except data is stored with 2 differenty parity bits. This means that 2 disks can fail and data is still recoverable. The size of the virtual disk would be the size of the smallest disk * 6.
In RAID 10, is groups of disks in RAID 1 combined in RAID 0. This allows for the possibility of multiple disks to fail as long as they are not in the same RAID 1 group. The size of your RAID 1 groups will determine the final size of the array.
Note not all RAID Controllers support RAID 5 & 10, but according to dell your controller does support RAID (0,1,5,6,10)
(http://www.dell.com/learn/us/en/04/campaigns/dell-raid-controllers)
Hot Spares are used as spare disks in the RAID Array. When a disk fails, (assuming it is a recoverable error) the array will recreate the data that was on the failed disk on the hot spare.
Overall I would recommend NOT using RAID 0 unless the information you are storing in VERY UNIMPORTANT. If ANY of the 8 disks would fail, it would mean the loss of all of your data.
RAID 1 as you have found out crates many duplicates increasing read speed, but there is really no reason to put 8 disks in RAID 1.
I would recommend either doing RAID 5, 6, or 10 depending on the disk space your require and the data integrity needed.
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