[NFBCS] it's a raid

[Aaron Cannon]

I do not believe that this is correct. Raid 10 is a combonation of striping and duplication. So, to make things simple, let's say that you have 4 1TB drives. If you used raid 0 on these four disks, you would have 4 TB of usable space, but no redundancy. So if you lost even just one disk, you would lose all your data. However, your data would be extremely fast to read and write. In a raid one configuration, you would have 2 TB. This is because two of the drives would be bit-for-bit clones of the other two. However writing would be twice as slow, though reading could be twice as fast, depending on the controler.

A raid 10 configuration would give you 2TB also, but would be faster for reads, because it combines raids 1 and 0. So you have data striping and data mirroring.

Raid 5 will be the slowest for writing, but gives you the best of both worlds in terms of read speed and durability, as well as utilization of your disk space. In short, a raid 5 array has 3 data disks, and 1 parity disk. This means that you get 3TB of storage, and you can lose one disk without losing any data. It basically uses each block on the data disks to calculate a parity block that gets written to the parity drive. Then, if you lose the parity disk, you are fine because you still have the data, and if you lose one of the data disks, you can use the parity block and the two remaining data blocks to solve a linear equation, to get back the missing data block.

Raid 6 is like 5, except that it uses two parity disks.

So to answer your question, if you have two disks, use raid 1. If you have more than 2, use raid 5, and if you have 4 or more, and are paranoid, use RAID 6. I've never seen a situation where the added risk makes raid 0 or 10 worth it, though I could imagine  a situation where raid 0 could make sense if you needed to do data processing on a large dataset that was backed up elsewhere. Raid 10 though, that seems much less likely.

Also, I would recommend, if at all possible, doing raid in software, not in hardware. The problem with hardware raid is that the vast majority of controlers are generally inflexible, so resizing is hard or impossible, and if your raid card dies, you have to get the same exact model to replace it. It used to be the case that computers were too slow to make software raid practical, but this is no longer the case. I personally use snapraid, which is not a realtime raid solution, but it works for me. I have it running in a raid 6 configuration, because I am paranoid.

Good luck. Hope this helps.

Aaron
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> On Dec 5, 2020, at 21:06, Littlefield, Tyler via NFBCS <nfbcs at nfbnet.org> wrote:
> 
> This depends a lot on what you want. I use 10 because it stripes, which is faster and gives you one extra drive. there's 50, etc but 5 will require more drives for redundancy.
>> On 12/5/2020 9:13 PM, Bryan Schulz via NFBCS wrote:
>> Question
>> 
>>  
>> Anyone have experience with configuring raid for hard drives?
>> 
>> What is better? 5 or 10?
>> 
>> Bryan
>> 
>>  
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