Originally Posted by the_beast
I meant you still need 4 drives for both. But you also don't need the PERC at all for RAID10 providing you have the requisite 4 ports on your mobo, which give you cash for extra drives or just means your $95 better off.
With small writes on a RAID5 array you have to first read the data off the drives, recalculate the parity then write back to the array. For the RAID10 array you just write the new data to the array. Which means small writes end up taking roughly half the time on a RAID10 than a RAID5 for 4 drive arrays.
Reads and large (larger than a full stripe) writes take about the same time on each (a 3-drive RAID5 and a 4-drive RAID10) as there are the same number of 'active' drives and there is no I/O overhead involved.
Makes sense. I don't have the extra ports on the motherboard though, so I do need a controller regardless. I have a 2-drive array on a cheapo controller, and 4 SSD's plus a VR on the motherboard ports, so I only have one open SATA port at the moment.
- More convenient to replace dead drive (can use one as hotspare, would take three drive failures to kill array)
- Slower small write speeds
- Takes longer to rebuild array after drive failure
- Faster small write speeds
- Could kill array with two drive failures
- Rebuild array more quickly after a drive failure
At this point, I'll probably go with RAID10 on the PERC 5/i. The PERC 5/i because I know it is a reliable controller, and a decent 4-port controller on newegg is almost as much anyway. I'll run performance tests in both modes (RAID10 and RAID5) just to make sure it matches with my expectations.