4x HDD's

[Savell Martin]

Hi guys,

Im setting up a new FreeNAS box and wondering the complications of this.
I have 4x 3tb WD Red's.

I want to set them up in Raid5 as it were so RaidZ
But it says that its not a recommended setup.

I dont mind if I lose all this data, but I would like a HDD to act as a hot spare incase there is a drive lose.

Would I notice an impact on my volume by running RaidZ with 4 drives?

 

[Trianian]

It's strongly recommended that the number of drive prior to parity be an even number. Your current plan would make that an odd number, 3 drives (before parity) plus 1 drive (parity). The box will work, but it may not work all that well.

With your 4 drives, you have two choices. Run RAID Z2 and sacrifice half your raw storage, or add another drive and implement RAID Z1, increasing your current net storage plans.

I was faced with this same situation when building my first box After doing a lot of research, I decided to order a 5th drive in order to properly implement RAID Z1.

 

[cyberjock]

Many people would say a 5 disk RAIDZ1 is asking for trouble. If you have to replace a disk and any other disk in your vdev has ANY problems during the resilvering, you can start kissing data goodbye. Just as the article title from 2007 said, RAID5 stops working in 2009.

 

[Trianian]

Many people would say a 5 disk RAIDZ1 is asking for trouble. If you have to replace a disk and any other disk in your vdev has ANY problems during the resilvering, you can start kissing data goodbye. Just as the article title from 2007 said, RAID5 stops working in 2009.

I'm know, and I'm ok with that.

RAID five /= RAIDZ1, not exactly

Given my scrubs, SMART tests, and backups of critical information, I'm not concerned. For critical uptime, yes, I'd also recommend RAID Z2 or 3.

 

[cyberjock]

It's not just about uptime. If you lose redundancy and the zpool metadata gets corrupted you could potentially lose the entire pool. An unmountable pool is a very bad thing. That has happened to so many people I give the warning(and many people ignore it anyway until its too late). But at least I warned them.

Even with good backups, I'd hate to be the schmuck with a 30TB pool having to recover from backup.. that would REALLY suck. Especially when adding an extra disk isn't very expensive. :)