RAID 5 v RAID 10

Hey guys,

I currently have a QNAP TS-451 NAS with 4x4tb drives running in RAID 10, so around 8tb of usable space. I'm considering reformatting and going RAID 5 so I can boost the space to around 12tb, has anyone else done this or is using RAID 5?

I'm running Synology's version of RAID 5 on my 5 bay NAS. Yes, you get more space since only one drive's capacity is lost to redundancy, but you also get less redundancy. It's always a tradeoff. What's your tolerance for losing the array?

mike_d wrote in post #18536806
I'm running Synology's version of RAID 5 on my 5 bay NAS. Yes, you get more space since only one drive's capacity is lost to redundancy, but you also get less redundancy. It's always a tradeoff. What's your tolerance for losing the array?

It's hard to say really, I just want to simplify how I store my photos. I'm currently doing a spring clean and eliminating all the clutter, then will compile all my images off my external drives and into one big catalog on the NAS. Then use the spare external drives to make backups of the most important shoots – weddings, workshops etc.

I assume you've read a number of articles on RAID5 vs RAID10? RAID10 is going to be safer and easier to recover.

What is your reason for using RAID? I use what's effectively a RAID mirror to protect against data loss during a drive failure. I also have careful and extensive backups.

Raid 5 is great for capacity with a side benefit of some parity/redundancy. It’s “slower” than raid 10 though.
You can’t lose more than one drive in a raid 5 array, so if there’s spare functionality NAS you should use it.

Raid 10 is quick for sure but it really gobbles the gigs to accomplish what it accomplishes.

mike_d wrote in post #18536806
What's your tolerance for losing the array?

^^^ This!
I regret going RAID 5 on my (personal) NAS. I have good local backups and for me it is not very important to have a high uptime reliability of the NAS. Now, I just have 25% less storage space for no real useful benefit. Additionally, the load on my NAS is not very taxing on the HD so that the probability of loosing one of them is fairly low (WD red). Your miles might vary - but RAID is not for data safety but only for uptime - and this is what you need to keep in mind for making your decision.

Is there any reason to use RAID10 over RAID6? I think RAID6 is even safer.

I'm not familiar with the Qnap from personal use.

My experience with RAID 5 is that unless you have a very high end high performance controller, it is significantly slower than RAID 10 (or 0+1) in use, and even more slow when a rebuild is required. Rebuilds taking 24 plus hours are possible (depending on TB and controller) Where as with RAID 10 a rebuild will be similar to the time it takes to simply copy one HDD to another.

So the decision comes down to capacity vs. speed.

I choose speed

*Note, in my case, the RAID is my WORKING active array. It is not a back up archive.

eelnoraa wrote in post #18539391
Is there any reason to use RAID10 over RAID6? I think RAID6 is even safer.

Speed. Also, if only 4 drives are used, you gain no increase in capacity vs. RAID10

I think for most NAS, the speed is bottle neck by the LAN speed by far. Normal usage, I don't think the read speed matter much, right? I agree the speed for rebuilt, but this should be a rare event.

eelnoraa wrote in post #18539406
I think for most NAS, the speed is bottle neck by the LAN speed by far. Normal usage, I don't think the read speed matter much, right? I agree the speed for rebuilt, but this should be a rare event.

This is true, thus I edited to add my note about my own uses being non archival non-NAS.

IC, understood.

My NAS is also acting as an centeral data repository at home, not for backup purpose. I have enough drive space and currently with RAID5. When I swapping the drives out, I kind of the added security of 10 or 6. I am leaning toward 6 because I can afford to lose any two of out 4 drives. With 10, it has to be 1 drive in each pair. However, I don't know if going to 10 will improve performance in my usage, if so, I think 10 is also a consideration