Expanding RAID with smaller drives

[bryce]

Couldn't think of a fitting title for the question, it's close enough though.

Anyways, I have 4 drives right now (500gb, 750gb, 640gb, 2tb). I 100% understand that I will be using usable space if I raid these drives together, but what I don't know is when I go and upgrade my drives and replace them with bigger drives will it be possible to swap say a 500gb out for a 3tb drive and a few weeks down the road do the same with another drive and still have my data in tact and just have the raid size adjust on the fly to the new usable amount.

Or is that impossible and I would need to physically recreate the RAID and lose all my data? I'm short on money right now and I really would like some kind of data security and it's just a mess having 4+ harddrives in your system being monitor, at least for me lol.

Or is it possible, but the amount of space I would lose in the process would not make it a viable idea to do seeing how I do have the 2tb drive 90% full and the other drives are about half full.

 

[Yatti420]

Based on your drives if you put them all together in a pool you would have ~500gb of usable space.. You will get the smallest drive amount in the system.. Just get enough 2tb drives to do a raidz2.. You are bettter off just doing it right the first time then risking failure with older /odd drives etc.. Raidz1 is out of the question for safety..

 

[joeschmuck]

What is your goal for your NAS, what size and what is your expected usage? This will help give you the best answer for your case.

Simple answer is yes.

To expand on this a little: If you start out with 4 hard drives like you mentioned and created a RAIDZ1 you would have 1.4TB of storage. If you went with a RAIDZ2 you would have .9TB of storage. Your limiting factor will always be the smallest drive in the group, so all drives will be treated as if they were all 500GB drives. Once you have created your pool of drives and even if you have data on them, just replace one of the drives (following drive replacement instructions in the user manual), lets say you replace the 500GB drive with a 3TB drive, now your new drive will be rebuilt and all drives will act as if they are 650GB drives, again the smallest drive in the pool, and your storage will jump up to 1.2TB for a RAIDZ2. Next replace the 650GB drive with another 3TB drive and your pool jumps up to 1.4TB of storage. Replace the 750GB drive with another 3TB drive and your pool now jumps up to 3.6TB of storage because all the drives are being treated as 2TB drives. You replace the 2TB drive with a 3TB drive and you now have 5.5TB of usable storage for a RAIDZ2. If you did the same thing with RAIDZ1 you would end up with 8.2TB of storage.

So knowing how much storage you need is crucial in the beginning. I started out with six 2TB drives in a RAIDZ2 configuration giving me 7.3TB of storage. I have filled it up to 5TB and I doubt I will need more, but if I did I could double it by replacing my drives with 4TB drives one at a time over the period of several months as I can afford it. In my situation I would never see a gain until I replaced my last 2TB drive with a 4TB drive, at which point it's doubled.

Because you will not start out with a large storage pool in the beginning if you use those drives you specified, you could always rebuild your pool if you can save off your data to another device.

I didn't mention anything about what type of hardware you were going to use but if you are going to use your NAS for any valuable data, ensure you end up running ECC RAM and backup your data periodically.

 

[bryce]

As for the hardware I'm running it on is my older desktop machine. i7-3770k, 16gb ddr3 1600 ram, the usual. Why the ECC suggestion?

And thanks for the RAIDZ1 and Z2 suggestions. I'll look into those and see which one fits my needs more. As for what I'm using it for is, to put it simply, everything. All my other machines will have their Libraries on this machine, all my music, movies, games, etc on it. To be honest there's nothing I truly can't live without as I can just get it all over again, it'd just be a pain, but I do wish to minimize that as much as I can with the dime budget I do have.

Now, for off-site backups, what about eventually adding a second NAS for on-site backups? Like a small, portable unit that I build myself? But then again that's probably defeating the purpose of true off-site backups.

 

[gpsguy]

You can read about it in the ECC vs non-ECC RAM discussion

Why the ECC suggestion?

 

[joeschmuck]

FreeNAS when done correctly is not cheap. Most of your costs are in the drives but that would be true of any NAS you built or purchased. Read the link gpsguy provided above.