New to RAIDz, need a little Help

[denaba]

Hello everyone. I have a lot of 8TB drives that I want to use these in RAIDz. Never done this before I played with Stripe a few times; never nothing happened. But with these HGST drives I started thinking why not? And some lady luck on my side for once

I actually have eight thanks to my job where they bought these 8TB drives. The manager is getting all new 12TB drives (thanks to corporate) so the 8TB drives are no longer needed. They never got plugged in or nothing so still in packages when I got them. I have done Short and Long tests and they came out fine

So I thought, why not make a RAIDz with these so a couple of questions came to mind;

Q1 - I believe the minimum is 3 drives (2+1), is this correct?

Q2 - If I stay at 3 drives what will be the available space? 16TB (or a little less for the adjustment)?

Q3 - If I get more drives then will it be easy to just add to the pool?

Q4 - My understanding if there are more drives; not confirmed if used or not. If they are the 8TB variety and not used, I am wondering then if I make a RAIDz now with what I have, add my movies to the pool can I later (if there are more drives) go for RAIDz2 from RAIDz without losing data? If no then I can wait to find out what the other drives are.

Q5 - Maybe from Q4 I should ask another question. Only one to two systems access the pool for the shows at any given time. Would RAIDz then be just fine? Or better to use RAIDz2? I get the whole replace a drive when a drive goes bad, but I am also thinking about only 1-2 system access the shows so the server is really not be hammered by like 15 systems accessing it. I only use it for shows, no VM's, no jails just one big storage.

I also have another TN and it is the backup to all this so moving files around is not a problem. Just wondering now that I got a bunch of drives I can learn a new way; RAIDz or RAIDz2 (if I the more drives are the same)

Thanks

 

[danb35]

Q1 - I believe the minimum is 3 drives (2+1), is this correct?

Correct.

Q2 - If I stay at 3 drives what will be the available space? 16TB (or a little less for the adjustment)?

Also correct.

Q3 - If I get more drives then will it be easy to just add to the pool?

Depends. There's no way* to turn a 3-disk RAIDZ into a 4-disk RAIDZ without backing up the data, destroying the pool, rebuilding it, and restoring the data. But if you wanted to add another RAID group of three disks in RAIDZ, that's fine and easy.

go for RAIDz2 from RAIDz without losing data?

No, no way to do that either.

*Well, you could create a degraded 4-disk pool--but that's all kinds of risky.

 

[denaba]

Thank you for the reply danb35. So doing the RAIDz with one pool on it; I cannot expand later on like when I find out of there are more drives available from our other building.

I thought of some other questions

Q1 - If I do RAIDz, is there a maximum amount of disks that I can do? Example, 7+1 or 9+1, etc.

Q2 - any advice on if I should RAIDz vs RAIDz2 since all the TN box does is have 1 or 2 computers accessing the shows? This is a home server.

I just saw a thread where someone is asking something similar and it seems like using RAIDz is still not a good option. Forum members stating that during the resilvering if another drive has an issue then all may get lost still.

Hmmmm, I guess I need to wait and find out if I can get more drives (crossing fingers and toes) so I can just do one setup since I will not be able to expand from a 3-disk RAIDz to a 4-disk RAIDz later on (unless like you mentioned; destory it, add a drive, create the new pool and then copy back the data).

Thank you again danb35.

 

[danb35]

If I do RAIDz, is there a maximum amount of disks that I can do? Example, 7+1 or 9+1, etc.

Too-wide vdevs tend to result in very poor performance as the pool fills--generally ten disks/vdev is considered about the limit.

any advice on if I should RAIDz vs RAIDz2 since all the TN box does is have 1 or 2 computers accessing the shows? This is a home server.

It really depends on your risk tolerance, but most of wouldn't recommend RAIDZ1 for disks larger than 1 TB or so.