Spanning 2 raidz1 vdev, 1 non-optimal

[onekanoobie]

Hello,

I have been searching the forums and online and have found several articles and posts that discuss the possible configurations and the pros and cons of each. The best solution for my needs seems to be creating 2 vdevs of 5 disks using raidz1. This would give me good performance, decent protection, and greater flexibility to grow in the future.

Now to the issue. I currently have 5 2TB drives, that would be vdev number 1. My second vdev would be made up of 2 3tb drives and 3 1tb drives, which I plan to upgrade to 3tb over say the next 4-6 months. Initially this gives me 12tb of usable storage space, but I am concerned about the performance hit of using a non-optimal set up for the second vdev. For the time being should I just create the first vdev of 8tb and hold off on adding the second until I have all 5 3tb drives? Or will the performance hit be negligible?

The NAS is used only for my home use, its main job is to stream videos and for personal data storage.

I really appreciate any ones thoughts on this. It seems to me that the performance hit for non-optimal vdev wont be to significant but this is my first set up with zfs. Thanks again for any advice.

**Edit**
Sorry I forgot to add that the 1tb drives are 512 byte sector while the 3tb are obviously 4k. I have read that this can hurt performance as well.

http://icesquare.com/wordpress/how-to-improve-zfs-performance/#section3

 

[willnx]

For home use and large files it's kind of hard to configure the HDDs such that you can't saturate a 1Gbe link.
What's more likely to cause performance problems is a lack of RAM, using a Realtek NIC in the FreeNAS box, or setting up a SLOG (when you don't need one).

Having said that...

Please don't do Raidz-1. It's a matter of when, not if, you'll suffer a 2nd disk failures while resilvering. Cyberjock has beat that horse to death.
Here's a link to why to use Raidz-2 (take right from his forum sig) http://www.zdnet.com/blog/storage/why-raid-5-stops-working-in-2009/162

 

[onekanoobie]

So your advice would be to use my drives in the same manner but instead of doing 2 vdev as raidz1 instead make them both raidz2 and take the hit on space. I had not considered that due to the user guides suggested number of drives for optimal performance for raidz. However I like the increased protection of that set up. Thanks for the advice.

 

[onekanoobie]

sorry to add on to this post but I a slightly different follow up question. I have been searching around and have found lot of information about upgrading the size of drives in a vdev to expand that vdev available space. For instance a raidz2 with 6x2tb drives, swapping them out 1 at a time with 3tb drives to expand the space. Out of curiosity if you were to start with a raidz2 vdev with 1x1tb, 4x3tb and 1x4tb drives, you would start with only 4 tb of space since the smallest drive is only 1tb. If you then swapped the 1tb drive for a 3tb, or a 4tb, would gain back all of the wasted space with the exception of the 4tb, since now 3tb is the smallest drive, or does the expansion only kick off when all of the drives are equal?

 

[SweetAndLow]

You first example

 

[onekanoobie]

Thank you very much. I appreciate the response.