Setting up the drives on my HP ProLiant Gen8

[danb35]

So I can just raid-z2 the 4x 6TB drives and I won't actually 'lose' 12TB from the 2 drives being 'used' to make it raid-z2, as the parity is across all drives aswell as data?

If I understand your question correctly, no. The general formula for RAID capacity is (n - p) x c, where n is the total number of drives, p is the number of drives' worth of parity, and c is the drive capacity. With RAIDZ2, p is 2. Thus, a 4 x 6 TB RAIDZ2 pool will have a capacity of about 12 TB, or 10.8 TiB.

 

[SweetAndLow]

Thanks, I knew this but forgot at some point I think. So I can just raid-z2 the 4x 6TB drives and I won't actually 'lose' 12TB from the 2 drives being 'used' to make it raid-z2, as the parity is across all drives aswell as data?

Well, that makes things a lot better, if I have things right.

no this isn't how it works, you would lose 12TB of capacity. You need to read a lot more you don't seem to have an understanding of how things work. I explained that if you had 6 drives that are 6TB in size you would have 36TB raw but only have ~20TiB usable. So you are losing 12 TB for parity and some more space for other stuff. Notice i didn't say you would lose 2 drives that is because there is nothing special about the 12TB that you lose for parity that space is just used up between all 6 of the drives.

 

[paradoxiom]

no this isn't how it works, you would lose 12TB of capacity. You need to read a lot more you don't seem to have an understanding of how things work. I explained that if you had 6 drives that are 6TB in size you would have 36TB raw but only have ~20TiB usable. So you are losing 12 TB for parity and some more space for other stuff. Notice i didn't say you would lose 2 drives that is because there is nothing special about the 12TB that you lose for parity that space is just used up between all 6 of the drives.

Sorry, I do know these things, and I read through that whole powerpoint last night, I've just got a terrible memory (blame it on my adhd, lame excuse I know) but I must have just forgotten or gotten confused, as there's a lot to digest in the beginning when learning this stuff - I also happen to be learning guitar too so my mind is everywhere at the moment, so apologies for the mess.

How about this, as my usage for the HP ProLiant Gen8 will mostly be for home streaming / media storage / maybe a ZNC bouncer server / very low traffic http server (I think it can probably do these things right, with plugins?) what option would be best to use with my 4x 6TB WD Red drives in order to give me the most space / redundancy? My friend keeps telling me to just use RAID5 but I keep reading here that RAID5 is "dead" and not to use it etc, so what do you think I should do?

I am even thinking of just running them as single drives, that way I lose no storage space whatsoever, and if a single drive fails, all I lose really is a couple weeks worth of torrenting / hours of ripping DVDs, and won't I usually know long before a drive totally fails anyway to try and back it up before it does?

 

[JDCynical]

...
what option would be best to use with my 4x 6TB WD Red drives in order to give me the most space / redundancy? My friend keeps telling me to just use RAID5 but I keep reading here that RAID5 is "dead" and not to use it etc, so what do you think I should do?

(Apologies if I'm repeating what you may already know)

As always, it depends on your risk aversion and how important the data is to you.

• RAIDZ1 would give you the most space (18 TB raw), but when a drive fails, the chance of loosing the pool due to another drive failing during the resilver is greater than RAIDZ2

• RAIDZ2 would give you a lot more security when a drive fails (can withstand two drives dying at once), but you loose another 6 TB of raw space.

• RAID5 would potentially be the 'easy' way out, but it doesn't cover bit-rot, you still have the danger of loosing your pool during a rebuild, and there is also the RAID5 'write hole'...

...
won't I usually know long before a drive totally fails anyway to try and back it up before it does?

Not necessarily. SMART is not a magic bullet for failing drive detection.

I've had SMART throw warnings on drives that were failing, giving me time to replace it before things went totally pear shaped, and I've had SMART throw warnings after the drive stopped working.

It's simply not 100% reliable.

 

[paradoxiom]

(Apologies if I'm repeating what you may already know)

As always, it depends on your risk aversion and how important the data is to you.

• RAIDZ1 would give you the most space (18 TB raw), but when a drive fails, the chance of loosing the pool due to another drive failing during the resilver is greater than RAIDZ2

• RAIDZ2 would give you a lot more security when a drive fails (can withstand two drives dying at once), but you loose another 6 TB of raw space.

• RAID5 would potentially be the 'easy' way out, but it doesn't cover bit-rot, you still have the danger of loosing your pool during a rebuild, and there is also the RAID5 'write hole'...

Not necessarily. SMART is not a magic bullet for failing drive detection.

I've had SMART throw warnings on drives that were failing, giving me time to replace it before things went totally pear shaped, and I've had SMART throw warnings after the drive stopped working.

It's simply not 100% reliable.

Thanks.

I was told in the freenas irc channel that I should disable the onboard HP RAID controller in the bios (which I did a few days ago after reading that you should always do it with the Gen8 anyway) and that I should use the FreeNAS ZFS, which I believe is like a software version of RAID built into FreeNAS?

If all that is correct, how would I set it up using the volume manager to achieve each of those raid options? (when I decide on which one I want to use, and have the additional two drives installed also).

Thanks again, very helpful.

 

[Ericloewe]

Just select all the drives and then RAIDZ1 or RAIDZ2 in the drop -down list.

 

[Robert Trevellyan]

what option would be best to use with my 4x 6TB WD Red drives in order to give me the most space / redundancy?

You can't optimize space and redundancy at the same time, you have to make a choice.

Don't worry about not being able to remember everything you need to know about ZFS after one reading of the presentation, there's a lot to digest and it may take several readings, along with studying other material, before it begins to fall into place.

One thing I notice, you seem to be focused on using FreeNAS as the primary objective with ZFS (the underlying filesystem that features built-in software RAID) as almost incidental. In fact, FreeNAS is tightly coupled to ZFS, and you won't get the best from a FreeNAS system without a solid understanding of the basics of ZFS. A significant proportion of FreeNAS users (perhaps the majority) choose FreeNAS because it uses ZFS.

 

[JDCynical]

I was told in the freenas irc channel that I should disable the onboard HP RAID controller in the bios (which I did a few days ago after reading that you should always do it with the Gen8 anyway) and that I should use the FreeNAS ZFS, which I believe is like a software version of RAID built into FreeNAS?

Pretty much.

ZFS, and by extension FreeNAS, is designed around having direct access to the drives in the pool. A RAID card, hardware or fakeRAID, hide the drives from the underlying OS and add at least one layer of obfuscation/abstraction.

Trust what people are saying in here, trying to run ZFS with a RAID card generally ends in tears.

If all that is correct, how would I set it up using the volume manager to achieve each of those raid options? (when I decide on which one I want to use, and have the additional two drives installed also).

Others have already covered this, I'll just add that this info is also in the users guide. :)