9.3 Volume Creation Wizard automatic drive ordering

[SwampRabbit]

I have finally gotten around to working on my new FreeNAS server again, tired of it collecting dust due to work getting in the way.

And I am curious about something I noticed while creating volumes with 9.3.
I have two M1115s, one with 8 drives on it, and another with 4 drives.
da0-da07 on the first and da08-da11 on the second.

I created a single zpool consisting of two RAIDZ2 vdevs using the Volume Creation Wizard, named the pool and selected "Automatic - Pick reasonable defaults for available drives".

Doing it this way, it seems to not use contiguous blocks of disks for the vdevs.
It does not seem to be ordering the drives in any sort of logical order or splitting the drives up in any sort of order between the controllers.
Attached is what shows up under "Volume Status".

Using the Volume Manager I replicated the same thing, but selected 6 drives across, and two rows down. This gives me the same expected setup but orders the drives da0-da5 for one, and da6-da11 for the other.

I am under the impression that both methods probably do not make a difference, other than the one keeps the drives in sequential order, but I want to make sure I am creating them in the best possible way.

So my question is:

Does the Volume Creation Wizard check something behind the scenes to create the volumes in this sort of fashion that is better than me selecting the drives in the Volume Manager?

Thanks

 

[dlavigne]

Interesting. If it twitches your OCD, create a bug report at bugs.freenas.org and post the issue number here.

 

[SwampRabbit]

I wouldn't say it goes that far. ;)

I just would like to know if the wizard is building the pool through some sort of process that makes it determine this grouping is optimal.
If it is checking the disks, controllers, then does some sort of calculation then it is not a bug in my opinion.

Trying to give the system some credit in knowing what configuration is best until known otherwise.
I would think that it would split the disks up across the controllers as a way of reducing the risk of failure, but it doesn't look like that.

Possibly it is just random, but if it is doing something in the background, and it chooses this setup for a reason... than it would be good to know.

If it is just random, then I'll file a bug report suggesting it actually use a process, and do it through the volume manger in the mean time.

 

[Mlovelace]

I wouldn't say it goes that far. ;)

I just would like to know if the wizard is building the pool through some sort of process that makes it determine this grouping is optimal.
If it is checking the disks, controllers, then does some sort of calculation then it is not a bug in my opinion.

Trying to give the system some credit in knowing what configuration is best until known otherwise.
I would think that it would split the disks up across the controllers as a way of reducing the risk of failure, but it doesn't look like that.

Possibly it is just random, but if it is doing something in the background, and it chooses this setup for a reason... than it would be good to know.

If it is just random, then I'll file a bug report suggesting it actually use a process, and do it through the volume manger in the mean time.

I have noticed if you change the volume layout with the drag and drop feature a couple times it will randomly reorder the disk sequence. So, if you looked at a couple different layouts before committing your volume that may explain the non-sequential order.

 

[SwampRabbit]

I have noticed if you change the volume layout with the drag and drop feature a couple times it will randomly reorder the disk sequence. So, if you looked at a couple different layouts before committing your volume that may explain the non-sequential order.

My question is not about how it works with the Volume Manager. I have not experienced the drives being in a random sequence with Volume Manager.
No matter what I do with that, it always puts the drives in the sequence I select with the drag and drop function.

My question is specifically with the Volume Creation Wizard part of Initial Configuration Wizard.
Fresh install of 9.3 on brand new mirrored flash drives and only thing done was run the Initial Configuration Wizard.
Tested this several times and it does this when selecting "Automatic - Pick reasonable defaults for available drives".

I will try with some of the other options when I have time and see what happens.

Just wondering if the Volume Creation Wizard part of Initial Configuration Wizard would put the drives out of sequence because it detects that it is optimal in some sort of way.

 

[dlavigne]

Just wondering if the Volume Creation Wizard part of Initial Configuration Wizard would put the drives out of sequence because it detects that it is optimal in some sort of way.

You would have to read the source code to see if they are using the same logic. It is quite possible they are not as they were written a couple of years apart and quite possibly not by the same person.

 

[SwampRabbit]

I finally got back to checking out this oddity I experienced on my test lab.

Started the server (cold boot) and ran the wizard.
Choose "RAIDZ2" and click "next" through the rest of the wizard.
Choose "Confirm" and it goes through the "Volume Creation" process.

It created the pool with 2 vdevs just like the "Automatic" option with the disks not as contiguous blocks of disks for the vdevs.

But the difference now is the order is a bit more logical, although not exactly sequential.
The 2 M1115s are still set up as da0-da07 on the first and da08-da11 on the second, same as before.
But the wizard now used 4 HDDs from the first controller and 2 HDDs from the second controller when it created each vdev.
This is different from the screenshot in my first post.

I detached the volume, marking the disks as new, and started over.
This time I chose the "Automatic - Pick reasonable defaults for available drives" option again.
It created the vdevs by putting the drives in the same order as when choosing "RAIDZ2" from wizard.

I detached the volume, marking the disks as new, and started over.
This time I chose the "RAIDZ1" option.
I did this to see if it is somehow retaining some sort of drive order despite detaching the volume and marking as new.
It actually DID keep the drives in the same order as when using the previous RAIDZ2 and Automatic options.

I detached the volume, marking the disks as new, and ran the wizard again choosing "Automatic"
It created the 2 vdevs with the HDDs in the same order as RAIDZ2 and RAIDZ1 wizard options I just tested.

I don't know if this actually tells me something, but the drives are now in some sort of more logical order than from when I first
posted, and if this is what I should expect.

If it helps explain better I will post screenshots showing the wizard keeping the drives in the same order now when choosing both RAIDZ1 and Automatic
tomorrow, but I need to sanitize some info shown in them first.

So my question is now, is having the 2 vdevs spread as 4 HDDs from the first controller and 2 HDDs from the second controller in each vdev
an optimal configuration to increase performance or redundancy; or does it even matter and I should just put the drives in sequential order?

Thanks