Hot Spares in FreeNas 9.1

[cyclerider]

While learning about ZFS, I found this article and a few others talking about adding a hot spare to a mirror or other forms of vdevs. This article and other things I've read makes me think the best way for me to run a ZPOOL is a bunch of 2 drive mirrors and then silvering in a hot spare when i fear a failure on a disk or two when I want to upgrade the VDEV size. While looking through this forum, the newest post I could find about hot spares is nearly a year old and said that hot spares still don't work, but mentioned FreeBSD 9. Unless I'm wrong, FN 9.1 is based on FB 9, so does that mean hot spares are now working?

 

[Richman]

That should be in the manual I would think. I do remember someone posting in a thread and saying they had a hotspare sitting in a drive bay ready to go but I remember reading that even with FreeNAS 9.1 , it doesn't just start automatically. I am not sure about that as I may be thinking of a 5 bay that is full of five drives and you have to click a UI button to tell it your taking a disk out first .... in other words not hotwsappable and if that is what I was reading about it wouldn't pertain to this situation. This may not be particularly helpful but the only reason I responded was that I seen that nobody has yet.

 

[cyclerider]

That should be in the manual I would think. I do remember someone posting in a thread and saying they had a hotspare sitting in a drive bay ready to go but I remember reading that even with FreeNAS 9.1 , it doesn't just start automatically. I am not sure about that as I may be thinking of a 5 bay that is full of five drives and you have to click a UI button to tell it your taking a disk out first .... in other words not hotwsappable and if that is what I was reading about it wouldn't pertain to this situation. This may not be particularly helpful but the only reason I responded was that I seen that nobody has yet.

thanks for replying. I searched doc.freenas.org for "spare" and the 3 entires that came up didn't really answer my question. I saw a spare option when messing around with freenas, but I'm not sure that means that its been silvered in and is ready to go when you need it.

 

[Richman]

What else would it mean? I would think it would imply that but then I havn't built my first FreeNAS yet. Did you try searching the forum with those exact key words 'Hotspare' 'sliver' .... not sure what other key words would help at the moment.

 

[cyclerider]

it could mean that its there ready to go, but hasn't been silvered yet? But when I think about it, that doesn't really make sense.

i did a little searching, but I didn't find anything definitive.

 

[Dusan]

Guys, you have two definitions of a hot spare here. It can be a drive that is connected to the system (powered on) and ready to be used to replace a failed device. ZFS supports this via the spares pseudo-vdev (you can add such spare via the GUI Volume manager). However, there is currently no mechanism that would do the replacement automatically when a drive dies.
What the author of the linked article does is a little different. His pool consists of several mirror vdevs and when he thinks a drive is about to fail he extends that particular mirror by another drive (creating a three way mirror). The resilver starts intermediately and when the drive fails he just removes it from the mirror (going back to two way mirror). This was always possible in FreeNAS, you just need to do it via command line (add a drive to a mirror to create a three way mirror). Also, it only works with mirrors as it is not possible to change RAIDZ1 to RAIDZ2 (or RAIDZ2 to RAIDZ3). You also need to be able to accurately predict that a drive is about to fail -- it won't help you much if you add a drive to some mirror and a drive fails in another mirror.

 

[cyclerider]

that's just the answer I was looking for, thanks!