Number of file copies = number of failed drives for tolerance?

[karpodiem]

Hi there,

 

I'm using Stablebit DrivePool with 5x4TB drives. I'd like to have the configuration set so if two drives fail, my data is still intact. I believe this should give me 12TB of usable space, if the data is striped and made redundant across the appropriate number of disks.

 

Does Stablebit work in this manner? Basically, I'm looking to replicate the tolerance features RAID6 or RAIDZ2 with Stablebit (of course, these two RAID solutions are very different, but I think you get the idea)

[Umfriend]

Hi,

 

If you want to be protected against the simultaneous failure of 2 drives (for uptime that is, RAID and DP are not backup solutions), then DP will need three copies of each file ("x3 duplication"). AFAIK, only DP 2.x supports this. With 20TB of space, you would therefore have net storage of 6.67TB. DP does not do parity like RAID-6.

 

Umf

[Christopher (Drashna)]

Umfriend is correct here.

 

StableBit DrivePool does not use Parity at all. We use "duplication", meaning that we maintain copies of the files on different disks. THe advantage this has over RAID or other solutions is that StableBit DrivePool is a file based solution, and the files can be recovered without having the reinstall the software, and can be recovered using conventional Data Recovery tools.

The downside is, yes that the Pool uses up more space as compared to other solutions.  

 

And as Umfriend has said, you'd want 3x duplication. That means that the files are on 3 disks at any one time, so they should survive failure of up to two disks. (and will partially survive more depending on how the files are laid out).

 

Though, StableBit DrivePool 1.X (the WHS2011 version) has a command line utility that lets you set the duplication to higher than 2x, but the GUI (dashboard) does not.

 

 

Also, if you're worried about drive failure, then getting StableBit Scanner along with StableBit DrivePool would be a good idea too. The reason being that StableBit DrivePool will read the information from StableBit Scanner. And will evacuate a drive that Scanner marks as "damaged" (that it finds bad/unreadable sectors). Also, you can configure it to do the same with SMART errors, and to avoid putting data on drives that have exceeded their manufacturer rated max temperature. 

[karpodiem]

Thank you both for your explanations - that clears things up.

[Christopher (Drashna)]

you are very welcome.

 

If you have any other questions or need any clarification, don't hesitate to ask.