ZFS Best way to configue vdev's for ZFS pool

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Had a high level design question for the experts in the forum. I am planning to move a 40TB filesystem from Linux/EXT4 MDADM RAID6 array to a ZFS RAIDz2 system. The system is primarily a file server for a variety of media files like videos and pictures.

I have 12 4TB Hitachi disk drives to construct the array. With respect to the vdev configuration, what would be the best way to do it?

  1. One vdev with all drives in it - I read somewhere online that performance takes a hit in this configuration and ZFS behaves very well with small vdev's
  2. Two vdev's with six drives each - I would take a penalty of about 8TB of storage since I would lose out due to parity but I am OK with it if it substantially helps in the long run.
Please share best practices and thoughts about the same. Any thoughts on best configuring the zpool as well as the arrays are also welcome.
 
Do you need fast storage/lots of IOps, lots of redundancy, or a mix of both?

If you need raw speed and IOps, then consider doing 6 mirror vdevs (2 disks each). That'll give you ~24 TB usable space. You'll get the combined write performance of approximately six drives.

If you need raw storage without a lot of IOps, then consider doing a single RAIDz3 vdev (12 disks). That'll give you ~36 TB. You'll get the combined write performance of a single drive.

If you need a balance between the two, then consider doing a pair of RAIDz2 vdevs (six disks each). That'll give you ~32 TB. You'll get the combined write performance of two drives.

I wouldn't recommend going below RAIDz2 with drives over 2 TB. But, if you want to live on the edge, then you could go with three RAIDz1 vdevs (four disks each). That'll give you ~36 TB. You'll get the combined write performance of three drives.

Basically, the more vdevs you add to the pool, the better your overall performance will be.
 
Oko said:
Check out FreeNAS documentation. Those people really know what they are doing.
Click to expand...

Except, there's nothing in that documentation regarding how best to configure a ZFS pool using a certain number of drives; or recommendations on which type of vdev to use; or anything relating to creating pools other than how to do so via their GUI.

There's some excellent information on using FreeNAS in that link; just nothing around recommendations for configurations.
 
phoenix said:
Except, there's nothing in that documentation regarding how best to configure a ZFS pool using a certain number of drives; or recommendations on which type of vdev to use; or anything relating to creating pools other than how to do so via their GUI.

There's some excellent information on using FreeNAS in that link; just nothing around recommendations for configurations.
Click to expand...

Sorry that was new work in progress manual for the 9.3 release. Check out the current stable release.

http://web.freenas.org/images/resources/freenas9.2.1/freenas9.2.1_guide.pdf


Page seventeen IIRC.

Cheers
 
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