Hotswap capabilities using server hardware

[Jürgen Starek]

Hello everyone,

I am planning to set up a FreeNAS or similar system for a group of remote, not very computer-savvy users. For this, I have a Dell 2950 with PERC 5 RAID controllers and an external Dell PowerVault enclosure for a further 15 hard drives. Both are taken, along with the hard drives, from the scrap pile, so drive failures are to be expected at a higher than normal rate.

I have two questions about this project:

- On the forums and documentation, I found various different statements about the support for hot-swapping defective hard drives. Since I'll be far away from the install location and people on site would have a hard time changing pool configurations: Is there a way for me to configure FreeNAS so that drive faults and replacement look and feel just like replacing drives on a standard RAID configuration, i.e. the faulty drive LED blinks and replacement is done by just pulling the defective drive from the running system, replacing it and walking away?

- The RAID controllers on my server do not allow JBOD configurations, unfortunately. Does anyone have experience with the often-discussed alternative of using lots of single-drive RAID 0 arrays?

Many thanks in advance

Jürgen

 

[cyberjock]

I have two questions about this project:

- On the forums and documentation, I found various different statements about the support for hot-swapping defective hard drives. Since I'll be far away from the install location and people on site would have a hard time changing pool configurations: Is there a way for me to configure FreeNAS so that drive faults and replacement look and feel just like replacing drives on a standard RAID configuration, i.e. the faulty drive LED blinks and replacement is done by just pulling the defective drive from the running system, replacing it and walking away?

- The RAID controllers on my server do not allow JBOD configurations, unfortunately. Does anyone have experience with the often-discussed alternative of using lots of single-drive RAID 0 arrays?

Many thanks in advance

Jürgen

1. Failure LEDs don't come on by themselves unless your RAID controller specifically does that automatically. But, see #2
2. Yes, if you search the forums you'll find that the ZFS gods will probably smite your data the first time you have a problem. You shouldn't mix hardware RAID with ZFS, and that's precisely what that hardware does. So ditch the card and go with something like the M1015. There's tons of threads on what to buy if you want to look around. ;)

 

[Jürgen Starek]

Thanks for your quick reply.

1. Sorry, I'm of course aware that the LEDs will need to be controlled by the RAID controller, I phrased that badly. But what about the rest of the replacement procedure? Can FreeNAS handle drive replacements and pool rebuilds completely automatically? On pp. 133 /134, the current documentation states that manual intervention is necessary. But in posts like this (sorry, German only) it sounds like it wasn't...
2. Thanks for the clarification, I always read those warnings as "don't mix a proper 3-or-more-drive RAID with ZFS", but not as concerning also single-disk pseudo RAID arrays.

Cheers

Jürgen

 

[cyberjock]

I can't answer your question for #1 as I don't read German. FreeBSD does NOT support hotspare automatic replacement. If you are using ZFS with something like Solaris (illumos?) they *do* support automatic replacement. Each implementation of ZFS is slightly different and so you have to understand what applies to when. If someone says "I just did an automatic disk replacement with ZFS" that means nothing because they didn't really define the OS they use. But, based on that sentence I can tell you that they aren't using FreeBSD/FreeNAS because there is no automatic disk replacement with ZFS for FreeBSD/FreeNAS. :)

For #2, RAID is RAID. I can understand the confusion, but in this new world you are entering, its important to be technically correct and to try to avoid interpreting what is said as something else. People do it, and they've sometimes lost their data s a result. :(

 

[Ericloewe]

To clear up the question, hot-swapping is certainly possible. That's something you must validate before trying, though. Don't go around hot-swapping stuff that's not connected to a backplane, either (that's something a forum user learned a few months ago).

As Cyberjock said, automagic disk replacement isn't available in FreeNAS. You can have a warm spare always connected, but you'll still have to manually follow the drive replacement section in the manual.

For what it's worth, my system (pseudo-server-grade) does hot-swapping just fine - but FreeNAS will freak out if you improperly remove a disk. As I said, validate this during testing if it's a feature you want to use.