Proper Vdev and Zpool configuration.

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sYndax

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Nov 3, 2013
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Hey,

I'm currently building a new Freenas box and was wondering
should I set up a single vdev which consists of 8x3TB on RaidZ2
or Two 4x3TB on Raidz1 in the same pool.

Thanks!
 
Both would work; it's not like one is right and one is wrong.

The optimal configuration depends on your particular requirements - how much capacity, performance, redundancy you need. If you can explain a bit more about the context then we can make recommendations based on that.
 
There is actually some best practice logic behind deciding the number of disks in a vdev more than just what your storage and IO needs are. Use "power of two plus parity" rule to determine the optimal vdev configuration. with RAIDz1 you would want 3,5, or 9 disks per vdev. With RAIDz2 use 4,6,10,or 18 disks per vdev. I generally advise no less than RAIDz2 these days.

Permormance considerations should also be considered. Your IO will be determined by the number of vdevs you have. a single vdev will never have more IO than a single disk in the vdev can achieve. This can be offset with a cache disk though in L2ARC configuration, which is a great solution with how inexpensive SSD storage is now.

Here is a good article about this.
 
Concentric said:
Both would work; it's not like one is right and one is wrong.

The optimal configuration depends on your particular requirements - how much capacity, performance, redundancy you need. If you can explain a bit more about the context then we can make recommendations based on that.
Click to expand...

Well, the storage is mostly intended for serving media to my HTPC,
and running Plex/SABNzbd/Sickbeard for media aggregation.

I'm looking for 2 disk redundancy in general however I currently have only
5x3TB drives. If I choose to go the 8x3TB route I need to purchase additional 3 drives.

Is there a redundancy difference between a pool of two RAIDZ1 vdevs vs. 1 Vdev of RAIDZ2 ?
 
sYndax said:
Well, the storage is mostly intended for serving media to my HTPC,
and running Plex/SABNzbd/Sickbeard for media aggregation.
Click to expand...
I'm running something similar. I'd suggest plex/nzbget/nzbdrone though.
sYndax said:
Is there a redundancy difference between a pool of two RAIDZ1 vdevs vs. 1 Vdev of RAIDZ2 ?
Click to expand...
Yes there is a difference. Any RAIDz1 option will only have single parity, RAIDz2 has double, so you can lose 2 disks before data loss. With 2x RAIDz1 vdevs you can technically lose 2 disks before data loss,but thats a misleading data point, as you can still only lose 1 disks per vdev before data loss.

EDIT:I'd suggest hopping on #freenas on Freenode IRC if you want more up to date answers.
 
More vdevs = always better performance.

You will not get a noticeable pause when the superblock is written.
 
So if my pool consists of 2xRAIDZ1 and 1 disk fails the entire pool is dead?
Eventhought the 2nd vdev is intact?

Also can you find nzbdrone/nzbget plugins for freenas?
 
If 1 disk fails from either or both RAIDz1 vdev then you would have no data loss. If a 3rd disk fails on either vdev after that point then you would have data loss. However, keep in mind if 2 disks fail on either vdev you would have data loss.

I don't think there are plugins for nzbget/nzbdrone, but nzbget is in ports, which is easy to install.
 
so there is no redundancy risk in using 2xRAIDz1 vdevs?

Should I go this route or bite the bullet, purchase 3 additional drives
and just go for 8x3TB raidz2?
 
If random IOPS is not important to you, I'd prefer 8-disk raidz2 to 8-disk raidz1 with two vdevs.
 
sYndax said:
so there is no redundancy risk in using 2xRAIDz1 vdevs?

Should I go this route or bite the bullet, purchase 3 additional drives
and just go for 8x3TB raidz2?
Click to expand...

If a vdev fails, the entire pool fails.

You can have a pool with: 1 vdev with 2 drives in a mirrored state, 1 vdev with 10 drives in raidz2 state, 1 vdev with 5 drives in raidz1 state.

To you the pool will look like one giant amount of free space, however it is made up of the hard drives that comprise the individual vdevs. Each vdev is it's own system essentially, if you have the mirror vdev fail the larger pool will be lost, or any of the other vdevs. You can even add single drives as their own vdev but they offer no redundancy.

raidz2 is better than raidz1, no question. But the reason this is in issue is because you are reluctant to loose so much space in having a safe configuration in raidz2. More vdevs is always better, but it is expensive.
 
Like I stated before. For a home system it is most cost effective to stick with 1 vdev for a system with 10 disks or less. If you need more performance from your pool you gain much more from adding an SSD for cache than you would doing multiple vdevs and eating up usable space.
 
Krazypoloc said:
If 1 disk fails from either or both RAIDz1 vdev then you would have no data loss. If a 3rd disk fails on either vdev after that point then you would have data loss. However, keep in mind if 2 disks fail on either vdev you would have data loss.

I don't think there are plugins for nzbget/nzbdrone, but nzbget is in ports, which is easy to install.
Click to expand...

Any chance on getting help with installing NZBget/NZBDrone?

I'm a total newbie with freebsd/jails etc...
 
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