N00b questions about duplication/recovery

[TropicMike]

Hi all,

 

I just installed DP on my purpose-built NAS last night and have a couple questions.The NAS is running with drive level duplication enabled on 8.1 64-bit using the on-board Intel SATA controllers.

 

I understand that if I am running two drives, files exist on both drives, so if one drive fails, I know that I need to copy everything from the remaining drive and I 'rescue' 100% of my files.

 

However, i'm running 4 drives in the pool (all exactly the same size/brand/model), which is leaving me wondering what I would do in the above case of a drive failing?

 

I'm having a hard time explaining it, but imagine if I dump 500 files on the DP virtual disk (again, apologies if I don't yet have the terminology correct).  How are they distributed among the four drives?  How would I be sure to recover 100% of my files if a single drive were to fail?  I'm guessing that the data for the entire pool is still visible (read-only) so could back that up, but it's the whole pool rather than just the 'vulnerable' files.

 

Or, is it really something I'm over-thinking and once I 'remove' the drive from the pool, DP would re-balance everything among the remaining three drives so I'd still have 100% of my files, with redundancy, again?

 

I'm also guessing I could plop a replacement drive into the pool and it would rebuild?

 

I'm coming from a many year RAID background, so adjusting to the concepts of duplicating at the file level is just tripping me up a bit.  Thanks in advance for the help -- as I've been looking around these forums, I've been astounded at the friendly, knowledgeable support that is provided - kudos!

 

Mike

[Christopher (Drashna)]

Actually, if everything is duplicated, if one drive fails, you'll still have a copy of the files on that drive. And once you remove the missing disk, StableBit DrivePool will automatically start re-duplicating the data as needed (create new copies).

This is handled automatically and without your intervention. 

 

 

As for how the files are distributed, ... new files are placed on the disk with the most available free space. This ends up creating a kind of "shotgun effect", where the files end up all over the place.

We do have a "Ordered File Placement" balancer that fills up one (or two or more, with duplication enabled).

 

 

Also, by default, real-time duplication is enabled, so it means that any new files are written to both destination disks at the same time.

 

 

I think I've covered everything here. If not, or if you need clarification, don't hesitate to ask.

[TropicMike]

Thank you, Christopher!  The 'shotgun' effect is exactly what I was trying to describe.  

 

Again, it's amazing the level of support and "don't feel like you're looking down" on people that you all provide here.  On the FreeNAS forums and some other places, it's really very hostile.  That alone gives you a huge leg-up, plus having a really polished product.  I'll be ordering the combo-pack tomorrow!

 

Mike

[Christopher (Drashna)]

You're very welcome!

 

And just in case it's important, one of the balancers (the "Prevent Drive Overfill" balancer, specifically), will try to keep the drives at least 10% free (or 100GBs) to prevent any issues from overfilled drives. 

 

 

Just having a good product isn't good enough. You need to have good support for the product too.  At least, that's how we feel!

And treating people rudely just because they're newer to the product or don't have a lot of experience with it is a very good way to alienate people that would otherwise become huge fans of your product. Besides, you never know if somebody may know more than us, but are just unfamiliar with the product or just overwhelmed (I've been on the other end, so I definitely know that it makes a world of difference on how people respond).

 

 

 

If you have any more questions, don't hesitate to ask.

[ceasley]

Not to hijack the thread, but I have an add-on question to the OP's original question.

 

If I am *not* duplicating everything, how will I know which files are missing if a disk fails?  Any chance you could build in some rudimentary reporting or something to that effect?