Yes, the performance will usually be better with 6 drives instead of 4, but it depends on how much you need to protect the array from disk failure.
Drive limits are only imposed by controllers (mine limits me to 32 drives in RAID 6 for example). RAID level 6 – Striping with double parity. EXPLANATION RAID 50, also called RAID 5+0, combines the straight block-level striping of RAID 0 with the distributed parity of RAID 5. RAID 6 can withstand a double disk failure. [3] As a RAID 0 array striped across RAID 5 elements, minimal RAID 50 configuration requires six drives. RAID 5 is a good all-round system that combines efficient storage with excellent security and decent performance. A 6-disk RAID 10 could withstand between 1-3 disk failures (depending on which ones fail); a 4-disk RAID 10, 1-2.
Jun 16, 2010 #11 N. nitrobass24 [H]ard|DCer of the Month - December 2009. So far this guide have explained RAID 5 and RAID 6. It is ideal for file and application servers that have a limited number of data drives. Another alternative, depending on your controller, would be to do a RAID 6. In the next section, I will provide a comprehensive but simplified comparison of RAID 5 vs RAID 6. I can create one with 6 or 8, not 7. I am also unable to make a raid with 5 drives, which leads me to believe that odd numbers of disks are not eligible for raid 6. RAID 5 vs RAID 6 Compared. I'm running 2 x 20 drive RAID 6 arrays myself. The section will compare different features of both RAID levels. If you have ordered the Server with one of the High Performance Raid Controllers, use Raid 6 as it will use 4 Hard drives for Read/Write. RAID 6 has a minimum number of drives (4), but no theoretical maximum. This RAID level 6 is similar to RAID 5, but includes a second parity scheme that is distributed across different drives and therefore offers extremely high fault tolerance and drive-failure tolerance. Issue two has to do with the nature of RAID 5 and RAID 6 failures. RAID 6 is like RAID 5, but the parity data are written to two drives. I'm trying to create a raid 6 array on a VNX 5100 from EMC, however am unable to create one with 7 drives. If you use the cheap Raid Controller, you will have very low write Performance if you use Raid 6 or 5. If you're looking for a RAID card though, I wouldn't recommend Adaptec a whole lot. For this reason while RAID 5 requires a minimum of 3 disks RAID 6 needs at least 4 disks. If you configure Raid 10 it will only use 3 drives for Performance, the other 3 will just be the mirrors and wont add up to red/write/IOPS Performance.
We have 8 total, and I immediately carved one out for hot sparing, leaving me 7 data drives. Usable capacity is always 2 less than the number of … RAID 6 requires a minimum of four disks and a maximum of 16 disks to be implemented.