oneclear

Parity Drive - Pro's & Con's

11 posts in this topic

I have just built a Server to store and play my Media. I am trying out Unraid and being a retired gentleman I have the desire to learn about something other than Windows.

One question, is the Parity drive necessary if you have all your data backed up elsewhere? At present I have a Windows 10 as a server with Stablebit Drivepool which works fine but is a bit boring.

I don't use duplication, if a disk goes I will replace it and load my data again. I only have 50GB of photos and 1TB of videos backed up on external drives and the cloud.

So what do I lose not using a parity drive other than data protection? And if I don't use parity can I do away with the cache drive?

Or am I going against all good practice?

 

 

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No, you can run without parity fine.  You've obviously learned the most important lesson, the importance of backups!

 

What parity gives you is additional fault tolerance for this particular copy of your data.  If a drive fails, you replace it and using parity rebuild it exactly as it was.  That adds convenience when the next drive fails, and of course they all do sooner or later.  But so long as you have good and up to date backups, you can live without the convenience of parity assisted recovery.

 

And of course, without a parity drive you don't need a cache drive.  There are other uses for it, but that's of much less importance.

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I would add though that having parity is a good way to learn about an important feature of unRAID. That's one of the reasons I went ahead and added parity2 even though I only have 5 data drives. And having a cache drive is also "part of the experience" as far as I'm concerned.

 

If instead of learning about unRAID, you are really more interested in learning about Linux, then maybe some other Linux distro might be a better choice.

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I agree with trurl, unRAID is a "purpose built" rather than "general purpose" distribution of Linux.  You can certainly use it without parity but redundancy is part of the core value proposition of unRAID.  You'd want to take advantage of one or two of the unique features of unRAID or it would be more cost effective to try one of the free distro's.

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Posted (edited)

unRAID like Stablebit Drivepool, both perform file pooling. If for storage purpose only , you would found a bit boring too. ( like me ) ;-)

 

For parity, it relate realtime stuff which backup can't cover.

If you implement parity, you can easy swap out disk with rebuild, it much faster then copy.

 

I have 2 unRAID, main and backup, when I buy a new disk, I will swap out a disk from main and insert to backup server.

 

i.e. I buy 4TB, I can replace backup server 2TB x2, just 1 rebuild only.

 

Con's ? It may slow down the write performance of the array and cost for the extra disk(s).

Edited by Benson
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Thank you for your replys, I have in the past dabbled with Ubuntu Server and bits of programming stuff, I started with a Sinclair Spectrum and wrote a 10k line program for designing Cranes which I then converted to GW Basic to run on our companies Intel 286, I also used to program Paradox Database's moving on to Access when it came out. Long time ago.

I have decided to go for it and use all the facilities available so Parity and Cache it is for the learning experience, then onto VM's and Dockers (what ever they are).

I have four Seagate 4TB Ironwolf drives and a 250GB Sandisk Ultra II for the cache.

Would you use all four drives or one for parity and two for the array with one as a spare or do I gain anything by having three drives in the array?

I new you would put me in the right direction.O.o

 

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I just wanted to add that I maintain dual parity on my main server as this is the server which I need as little downtime as possible on - and the parity drives facilitate that (especially as disk sizes get larger and the number of disks in my array keeps growing). I however don't run my backup server with parity (anymore). Some might say this is a risk (and I guess that risk does exist) but the risk of 3 disks failing on my main server and one on backup at the same time (scenario where there would be data loss) in a 24 hour period is so unlikely IMHO given the regular preventative maintenance I also perform on the drives (however major the consequence would be) that I happily live with it!

 

EDIT: I also keep 2 x 8TB drives off site with absolutely critical data. I do this because my backup server is on site and thus would not protect the data from loss subject to theft,  natural disaster, fire or any other physical threat etc.

Edited by danioj
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4 hours ago, oneclear said:

Would you use all four drives or one for parity and two for the array with one as a spare or do I gain anything by having three drives in the array?

I can see going either way on that. My philosophy is to not buy more drives than I need, and if I need to replace one, I can buy it then at the latest prices. Others like to have a spare since they don't think they can afford any downtime.

 

Since you already have them, it might make some sense to only use them as you need capacity, but of course, the warranty is heading towards expiration whether used or not.

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4 hours ago, oneclear said:

I have four Seagate 4TB Ironwolf drives and a 250GB Sandisk Ultra II for the cache.

Would you use all four drives or one for parity and two for the array with one as a spare or do I gain anything by having three drives in the array?

Well the main consideration is how much data you want to store.  Assuming that you can store everything you need in 8TB of effective storage space I'd go with 1 parity drive and 2 data drives. After that 1 parity/1 data is a special case, but once you add the second data drive you're into normal unRAID operations.  Assuming you go with one parity drive and 2 data drives the remaining drive will be available as a spare when (not if) you loose one of the other drives (I like the idea of a spare).  You could also use it to play with dual parity in the meantime as a learning experience.

 

FWIW, I also maintain the 8TB drives offline/offsite approach for critical data.

Edited by tdallen
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That's the great thing about unRAID. It's your machine and you pretty much can bend the rules however you want. :D

 

I use a Parity Drive for Fault Tolerance and I built a machine that can hold 14 Drives off the Mother Board/Expansion Card, but currently only have 12 Bays for drives. So I reserved the the other two for SSD's simply because I can Velcro them anywhere in my case. I put in a few drives and when I need more data I just slap in another drive and if a new drive is cheap I can replace a smaller drive with a larger drive I will. Eventually I'll run out of Case Space or eventually swap out all my small drives for larger drives and begin consolidating. Just depends on the Wifes Approval Rating. lol

 

All my Critical Data like Pictures, Home Videos and important Doc's I have backed up 3X one being on the unRAID machine, 1 off site and 1 on a Portable Device.

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Just to make some think WTF to themselves, I run multiple 28 drive unRAID Pro machines and no parity disks in any of them. I have a couple spare disks per chassis I could throw in for parity just because, but I didn't buy unRAID for the parity. I was also a Windows/Drivepool guy coming from WHS2011. Since I didn't have parity on that, I grew accustomed to having a full identical backup in the event of a drive failure.

So I chose unRAID as a Windows guy wanting a point and click interface, add random sized drives (all mine are the same size) if I wanted to and just generally very easy to expand. It made everything very simple. I also don't use Docker or VM's as mine are pure storage servers. So I've never had a reliability issue with them, they just work.

Looks like your going to run parity, which is perfectly fine but there are more than a few of us that run no parity at all and are perfectly content. As others have said, it's a great run it how ya want type of system.


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