RaidZ with 4 Disks

[Frosch1482]

Hi,

today I installed my new WD 4 TB Red drives.
Freenas proposed to create a ZFS Volume "Mirror"...

I would prefer to have a RAIDZ just to get out out approx. 10.x TB from the 4 Discs.
As alternative I would create a RAIDZ2 with approx. to 6.9 TB

Obviously FreeNas warns me that a RAIDZ configuration is not ideal in case of 4 Discs..

According to what I understood right now:
- RAIDZ with 4 drives is slower than RAIDZ2
- Only one drive out of the pool can fail... If two fails: bye bye pool :)

I did some performance tests and the limit is in both cases (ZFS Pool with RAIDZ or ZFS Pool with RAIDZ2) the Gigabit network at my home. (We are talking about a home server)

I came to the conclusion that I can live with the fact that only one drive can fail. The performance in my Gigabit network is the same if I use RAIDZ or RAIDZ2. Using RAIDZ i have approx. 3.x TB more available disk size, which is quiet important for me.
Are there other facts that I have not considered?

Thank you for your help,
Regards,
Frosch1482

 

[cyberjock]

RAIDZ with 4 drives is slower than RAIDZ2

Not true, but you're probably going to be limited by your Gb LAN anyway.

Only one drive out of the pool can fail... If two fails: bye bye pool :)

Not true. And this is exactly why I have the RAIDZ1 is dead link in my signature. If 1 drive fails and you start resilvering and another disk has a single URE, that can spell completely loss of your pool. It happens more frequently than you want to realize. We've discussed the reasons why this is so common all over the forum. In short, if you plan to do RAIDZ1 I'd highly highly recommend you keep full backups because your days with that pool are numbered with RAIDZ1.

 

[Frosch1482]

Thank you for this hint. Unfortunately my english is not that good and I did not understand this when I read the advantages / disadvantages of the different RAIDZ´s

In simple words this means: If one disk fails of a RAIDZ or RAID5 and there is only one bad sector in one of the other discs, the rebuild of the RAIDZ will fail and the pool is gone...

In this case I will probably go to a RAIDZ2 ZFS system.

 

[cyberjock]

In simple words this means: If one disk fails of a RAIDZ or RAID5 and there is only one bad sector in one of the other discs, the rebuild of the RAIDZ will fail and the pool is gone...

It's not a "for sure" thing. You might only end up with a single corrupted file. But statistically, by watching forum users lose their pools, RAIDZ1 is just asking for problems. For that reason I put that in my sig and hope that people stop using RAIDZ1 because seeing people lose their data isn't something I enjoy reading about.