Help with RAID

Skydiver · March 19, 2016

So I am planning on building a NAS and I had decided I would use ZFS (with Free NAS) but having read numerous articles, I am starting to doubt my decision. I have looked into the different types of raid and would like to ask the community what they would recommend for my needs.

This is going to be a home NAS but we will store very important data that cannot be lost, along side trivial data. I wish to have acceptable read and write speeds. I have 2 HDD available now but would not mind buying others to make sure those files are secured.

Now a different question, are the consumer grade NAS 'safe'? Or is the diy approach the best to fit my needs?

Thx

Oshino Shinobu · March 19, 2016

Well, you're going to need at least 3 drives for RAID Z (I'm going to call it RAID 5 from now on, because that's what it is), but it only really becomes effective at 4 drives or more. For a NAS, you're almost certainly going to be limited by the network, not by the speeds of the drives. Unless you're using 10GbE network equipment, which is damn expensive, then pretty much any drive is going to be faster than the network speeds.

For a NAS, RAID is all about redundancy, not speed. If you have two drives available, then go for RAID 1, so all data is mirrored across the drives. You will only have the total capacity of the smallest of the two drives, but you can lose one without losing data. If you need the space of two drives, but don't want to buy 4 drives (either for RAID 5 or RAID 10) then going for either a JBOD or just have the drives as separate volumes is an "okay" solution. Just as long as you don't go for RAID 0.

If you're wanting to keep the cost as low as possible, then you could have a JBOD or two separate volumes, then set up a nightly backup of your important information to an external drive. Would be even better with the two drives in RAID 1, with a backup of the array.

For drives, you should always try to use NAS/RAID drives that are designed for those sorts of workloads. WD Reds would be my personal choice. The 24/7 operation in close proximity can kill your normal desktop drives pretty quickly, due to the nature of how NAS drives tend to be accessed, as well as the vibrations caused by other drives. If data security and integrity is a primary concern, then desktop drives should only really be used for things like backups, while the internal drives should be NAS class drives.

Skydiver · March 19, 2016

4 minutes ago, Oshino Shinobu said:

Well, you're going to need at least 3 drives for RAID Z (I'm going to call it RAID 5 from now on, because that's what it is), but it only really becomes effective at 4 drives or more. For a NAS, you're almost certainly going to be limited by the network, not by the speeds of the drives. Unless you're using 10GbE network equipment, which is damn expensive, then pretty much any drive is going to be faster than the network speeds.

For a NAS, RAID is all about redundancy, not speed. If you have two drives available, then go for RAID 1, so all data is mirrored across the drives. You will only have the total capacity of the smallest of the two drives, but you can lose one without losing data. If you need the space of two drives, but don't want to buy 4 drives (either for RAID 5 or RAID 10) then going for either a JBOD or just have the drives as separate volumes is an "okay" solution. Just as long as you don't go for RAID 0.

If you're wanting to keep the cost as low as possible, then you could have a JBOD or two separate volumes, then set up a nightly backup of your important information to an external drive. Would be even better with the two drives in RAID 1, with a backup of the array.

For drives, you should always try to use NAS/RAID drives that are designed for those sorts of workloads. WD Reds would be my personal choice. The 24/7 operation in close proximity can kill your normal desktop drives pretty quickly, due to the nature of how NAS drives tend to be accessed, as well as the vibrations caused by other drives. If data security and integrity is a primary concern, then desktop drives should only really be used for things like backups, while the internal drives should be NAS class drives.

So Raid 5 and Raid Z is the same thing? What about zfs? (sorry all this terminology really confuses me). As for Raid 1, it would not be suitable to stream media on the network, right?

Oshino Shinobu · March 19, 2016

16 minutes ago, Skydiver said:

So Raid 5 and Raid Z is the same thing? What about zfs? (sorry all this terminology really confuses me). As for Raid 1, it would not be suitable to stream media on the network, right?

Yes, for the most part. Calling it RAID Z seems silly to me, as it gets people confused. To be clear, it's not exactly RAID 5, as there are a few differences that makes RAID Z a little better. However, the way that they distribute data cross the drives is the same, and the way they work, fundamentally, is the same. It's easier to find information on RAID 5, so that's what I call it. Maybe RAID 5+ would be a better name.

ZFS is a file system. Basically, if you're going to be using FreeNAS and want anything more than just simple file storage, you're going to be using ZFS. It has a focus on protection against data corruption, along with support for high storage capacities and many types of software RAID. If you're going to be using something like Plex (or any other app/plugin), then you're going to need ZFS with FreeNAS, as plugins are not supported on UFS.

RAID 1 would be okay for streaming media on the network. It doesn't have any significant impact on performance, either positive or negative, so it's still going to be as fast as a single drive. How capable it will be depends on how many, and what size data streams you plan on having. As I mentioned before, the networking is most likely going to be the limiting factor. If you have everything wired up to a gigabit network, then the majority of drives are going to be faster than 1000Mbps anyway.

Performance issues can pop up when multiple users are accessing the NAS from different locations, if you're using desktop drives. NAS drives as designed for that kind of workload and cope with it well, but desktop drives can struggle with multiple users at once, as they're fundamentally designed with the expectation of only being used by one user at a time.

As a bit of reference, I can stream three 1080p, high bit-rate, FLAC audio movie files over the Gigabit network from a single drive I have setup in my desktop PC. I can do 4 as well, but time skipping on the videos becomes slow with that many. Saying that, it is a desktop drive, so it may be an issue with the load on it.

EDIT: You can see some of the differences between RAID 5 and RAID Z here: https://en.wikipedia.org/wiki/ZFS#RAID-Z