How does unRAID Parity works and why did I use it...?

HAPPY NEW YEARS!!!
Ok but for real, this is just a very quick, basic explanation of how unRAID parity works and why I chose it. I like it for what I use it for but I understand why other options would be better suited for some scenarios.

I am very happy with it and would do it again. :)

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[bradsw]

If you do a weekly parity check (which is the default), all the drives are spun up for the period that it takes to check the entire array). That gives you an (at least) weekly SMART check opportunity at least, or errors logged that you can act on. Have a good new year and enjoy your unraid!

[vampov]

Someone correct me if I'm wrong but the big selling point for me with unRAID is that you can add drives to a system or odd sized drives to the system at anytime. The problem with FreeNAS is you have to have all the disks symmetrical and set up before you set up the NAS. I might not want to have 10 TB of storage to start out with I might be fine with just 3 TB but instead I'm locked in to buying all this expensive hardware I don't need. And then if I do build a 4 hard drive FreeNAS and want to add more drives I have find a way to move all that data so I can start over from scratch to install all those new drives. It seems unRAID just gives you greater versatility and even though ZFS is badass I might not need all that security and performance it gives.

[DPrintingNerd]

Setting up unRAID now with a big bunch of drives, and glad I found your video that talks about even parity! Also, sweet Barnacules shirt :)

[christophermorris]

Just wanted to chime in, and say most of the downsides he's pointed out have been fixed, or have features to make it better. I actually moved from FreeNAS to unRAID for the flexibility, and features unRAID Pro offers today. I went with 12x8TB HGST 7200RPM NAS drives, and set 2 as Parity. I also used 2 SSDs for the redundant cache drive. Never has anyone complained about read, or write speeds from it, and they were using FreeNAS not but a couple days before I built/upgraded to unRAID. Also make sure to check out all the cool apps that help with speeding things up. If you are like me, and came from FreeNAS chances are you have a TON of ECC RAM. Well use just a bit of that to cache all the folders to RAM for instant access baby! :)

I also got a 24 3.5" bay Supermicro server with dual Xeons from ebay. Came with everything ready to rock, but the OS. I had to flash the LSI card to IT mode, and then I started adding all my old drives I had after I moved everything over to the new BIG 80TB NAS I was talking about above. I also set 2x4TB parity drives on there since 4TB was the biggest extra drive(s) I had. I have added most of the other 18 drives. The "preclear" process is legit. It found some issues on drives that came from my FreeNAS build that I knew where starting fail, and get bad sectors. Preclear found the issue, and I just set the drive aside. :) I use this box to mess around with VMs, and such. I also backup the REALLY important stuff from my new NAS to it. Then from there I have it sync the super super critical stuff to an external 8TB. It's always good to have backups! :P

unRAID fan for life!

[QuantumBraced]

I've never had an HDD fail ever going back to the 90s. Before the era of SSDs, none of my system HDDs ever failed, never had a storage HDD fail, I have my 200MB childhood HDD still, it's 30 years old and works like a charm. I guess I've been lucky. I mean HDDs definitely fail, but I think some people overstate the risk, it's usually 1 out of 100 drives will fail per year with an average use time of 3 months. But that's for drives that are being constantly utilized. Also, it includes drives that failed in the first month, which if you clear that hurdle the risk goes down dramatically for the next 5 years. Basically, if your drives aren't spinning non-stop and survived the 1st month, the odds of failure before 5 years are extremely low unless you expose them to crazy vibration or drop them or something. So I think for less than a 10-drive array, one parity drive is totally fine unless the data is absolutely critical, in which case you should also be backing it up in the cloud and maybe also cold storage. Also, with Unraid the data is not striped which is another big advantage.

[chrismoore]

ZFS also allows you to check and correct damaged files with the parity information that it stores. This allows data corruption to be corrected in the data at rest during periodic scrubs.
ZFS is the file system to ensure your data is not lost or corrupted and I can read and write to my array (z2) at Gigabit speed. The problem you are having with unraid is that it is only writing to one or two disks which limits you to the actual mechanical speed of the disk. Even a SATA-III hard disk can only write at about 120 MB/s. Because of the way my data is spread across multiple disks, I can read or write at a theoretical speed of 920 MB/s. The slowdown in most data transfer is the disk and in a server it is the number of disks. Where I work, we have a NAS (of sorts) that writes to over 100 disks so that the throughput of the disks is not a choke-point.

[AndyBradley]

I have ALWAYS used WD drives, mostly in some kind of RAID, from Raptors and Velociraptors all the way down to the Green drives and never ever had a drive fail on me in 15 years.

[camaromike]

@9:37, two data drives fail would not result in data loss if you have a 2 parity drive setup.

[djinkarnate]

Great vid as always. I am planning to use unraid in my new rig and virtualise a copy of windows 10 thanks to you and your videos in the last 2 months.

[SuperWolfkin]

boom 3 minutes exactly and I understand how parity drives work. That was super clear.

[erodz]

Unraid 6.2 has turbo write mode on disk settings. that significantly improves the write speeds. But all the disk have to be running at once.

[RockTheCage]

Excellent. 1000 thumbs up for you. Researching if i wanted to switch from my current setup to unRaid and your video help me decide. I'm going to research Synology and SHR a little bit but so far what i have now is wining. I have windows with Stablebit drive extender + stablebit scanner. Its actually been an excellent combination. Its not going to be nearly as efficient on space utilization as Unraid. Essentially it pools all your drives together and then you can pick how you want the redundancy to work. Say get get as granular as folder by folder and tell stablebit how many redundant copies you want to keep. 2x, 3x or you don't want it to keep a redudant copy of that folder. This way its very flexible so if you have a large folder than you know whatever is in that folder would be easy to redownload from the internet you can tell it not to duplicate that folder. If you have another folder that has VERY important info you can tell it to x3 that folder. The way it works is it pools standard NTFS drives together. If you tell it to x2 a folder it will make sure that folder is stored on 2 separate drives. If you tell it to x3 that folder it will be stored on 3 different drives. If something happens the drives are formatted with standard NTFS so you can easily pull data off the drives. So essentially its mirroring your data across different drives so in that way its less effecent in the other hand you can tell it folders you don't want to mirror so in that way its more efficient (of course how well this works is dependent on your needs). At the same time their drive scanner is awesome. Save my rear multiple times and emailed me warnings that it either found a bad block on one of my drives or my drive was overheating. The only thing is I wish it worked on linux. Not much of a windows lover :) but it doesn't.

[coryulrich]

Turns out those 35 megabytes per second on your WD reds we're probably because they were illegally selling misss branded SMR drives.

[johnmarkzimm]

I love that you can just add disks as you need more storage. And have you looked at all the cool Docker containers? Plex, crashplan, and many more! And it's way easier to set up, run and trouble shoot that the other nas options.

[Akshay]

Hey, can you please tell me how did you find errors on pre clear? Is it from SMART counts or you used something else?

[ElSarcastro]

Please correct me if I'm wrong, but if during a rebuild of a drive another one has a read error, then the rebuilt drive will just have zeroes in that specific sector and intact data otherwise, or do you lose all the data?

[JHess]

just out of curiosity, what are you using (software) to preclear stress test your drives and when you said you sent drives back for warranty was that based on the smart readings after the stress test or some other factor (physical fail)?

[tivor]

I first learned of unRaid from watching your videos, and it sounds like a very interesting mix of risk and reward. Very cool. Thanks for informative series of videos!

[thebenholmes]

I appreciate how well you explain these systems.

[benriful]

Again ... unRAID seems like it's using SnapRAID and some sort of Union file system. Actually pretty good. Though from what you're saying it seems to use the very old UnionFS by just filling one disk up and leaving the rest till they need to augment space.
IMO a better idea is MergerFS which has the option to spread files across all disks equally, even ballancing the loads to both improve speed as well as not overwork one single disk. Add SnapRAID onto that (1, 2, 3, however many parity disks you want) and you end up with the same redundancy.
Even better is that SnapRAID offers multiple versioning parity - you can even restore old files you happened to delete / overwrite. None of the others provide this feature. Again, pointy clicky install and admin on Open Media Vault - ideal for a noob building a home server. For a more tech savvy person I'd likely go with a Linux server and do it all on command-line.