unRAID fault tolerance

[wsume99]

Noob here and I just want to confirm what I believe I've read in some of the other posts.

 

First let me say that I am thoroughly impressed by the quality of this forum and the support that is provided here.  It's refreshing to see, kudos to lime-tech!

 

My main objective is to build a server to serve as the primary storage location for my music, DVDs, and recorded TV from my HTPC and as a backup for photos/home videos.  The primary storage location for the photos/home videos will be my main desktop.  So my objective is to have a stable, hassle-free, low maintenance, upgradeable home server.  I think that unRAID will fit the bill but before I take the plunge I'd like to confirm the stability/fault tolerance of unRAID.

 

1)  If I use a parity drive the system can lose any SINGLE HDD without losing any data, correct?

 

2)  If more than one drive fails the data lost is isolated to what was resident on the failed drives, correct?

 

3)  The software is registered to the USB drive it is first installed on, what happens if the USB drive fails?  Is my data secure? Do I have to purchase another license?

 

4)  If I have an operable system and want to upgrade the MB is this possible without losing any data or offloading the files to another system first?

 

5)  Is there any advantage to having the parity drive as a RAID 1 array?  I'm thinking not much.  Basically requires that you loose a data drive and both parity drives before data is lost, correct?  Is this even possible?  I'm guessing it would probably slow down writes to the server.

 

6) I have a spare Gigabyte board (GA-MA785GM-US2H) I'd like to use.  I assume it's ok so long as I disable the BIOS feature that writes an image of the BIOS to the HDD, correct?

 

 

I'm sure I'll have more questions to come but my plan is to start with the basic version to make sure I can get everything to play together and then upgrade to the pro version and add a cache disk once I've got everything up and running. 

 

Any advice would be appreciated.  Thanks in advance for all your help.

[Joe L.]

Noob here and I just want to confirm what I believe I've read in some of the other posts.

 

First let me say that I am thoroughly impressed by the quality of this forum and the support that is provided here.  It's refreshing to see, kudos to lime-tech!

 

My main objective is to build a server to serve as the primary storage location for my music, DVDs, and recorded TV from my HTPC and as a backup for photos/home videos.  The primary storage location for the photos/home videos will be my main desktop.  So my objective is to have a stable, hassle-free, low maintenance, upgradeable home server.  I think that unRAID will fit the bill but before I take the plunge I'd like to confirm the stability/fault tolerance of unRAID.

 

1)  If I use a parity drive the system can lose any SINGLE HDD without losing any data, correct?

Correct

2)  If more than one drive fails the data lost is isolated to what was resident on the failed drives, correct?

Correct

3)  The software is registered to the USB drive it is first installed on, what happens if the USB drive fails?  Is my data secure? Do I have to purchase another license?

Your data is secure even if you decide to just access it 2 drives at a time.  The other part of your question is answered in the wiki here:

http://lime-technology.com/wiki/index.php?title=FAQ#If_my_flash_drive_dies_or_is_lost.2C_will_I_lose_my_license.3F

4)  If I have an operable system and want to upgrade the MB is this possible without losing any data or offloading the files to another system first?

Easily.  Done every day.  You'll probably need to use the "Devices" page to re-assign the disks to their respective slots in the array since the hardware is scanned in different order on different motherboards.  To assist in that, make sure you take a screen shot of the "Devices" page when you make configuration pages.

5)  Is there any advantage to having the parity drive as a RAID 1 array?  I'm thinking not much.  Basically requires that you loose a data drive and both parity drives before data is lost, correct?  Is this even possible?  I'm guessing it would probably slow down writes to the server.

No benefit.  The parity drive is no more important than ANY OTHER DRIVE.  If you lose two data drive and have a perfectly healthy parity drive you've just lost two data drives worth of data.  A RAID1 parity drive does not help.

6) I have a spare Gigabyte board (GA-MA785GM-US2H) I'd like to use.  I assume it's ok so long as I disable the BIOS feature that writes an image of the BIOS to the HDD, correct?

Actually, no.  You are not OK, or rather, you might think you are until the CMOS battery dies and the BIOS reverts to its enabled state.  Then the next time you reboot the BIOS will make one of your drives smaller, effectively, to unRAID's OS the drive is a different drive.  If it picks the parity drive, then it might not be the largest drive any more and the array will not start.  If it picks a data drive it might overwrite your data and make the drive look like a different drive to the OS.  Since the partitioning no longer matches what is expected, it might be identified as a foreign drive and be a potential candidate for clearing.  (writing zeros to the entire drive)

 

Still think you want to bet how long the CMOS battery will last?

I'm sure I'll have more questions to come but my plan is to start with the basic version to make sure I can get everything to play together and then upgrade to the pro version and add a cache disk once I've got everything up and running. 

 

Any advice would be appreciated.  Thanks in advance for all your help.

Good luck...  and have fun learning.

[wsume99]

Thanks Joe for the reply.

 

I've been doing more searching and found the FAQ page - it helped A LOT.  Tons of useful info there.

 

With regards to your reply to #6.  Here is the description from the manual..

 

Backup BIOS Image to HDD

Allows the system to copy the BIOS image file to the hard drive. If the system BIOS is corrupted, it will be recovered from this image file. (Default: Disabled)

 

I checked the setting on my board and it is currently set to 'Disabled'.  I know that I've never changed it so it must be true that it's default setting is in fact 'Disabled'.  That said, if the CMOS battery dies then the BIOS would be reset to all Default values and it would not write a BIOS image to any of the HDDs, correct?  The only way this would ever happen is if I changed the setting to Enabled.  So it would seem that I might be ok to use this board without living in constant fear of a dead CMOS battery.

 

Also, is the Backup BIOS Image to HDD feature I'm asking about the same as the the HPA issue discussed here that makes some users dub Gigabyte boards as "unRAID poison"?

[Joe L.]

Thanks Joe for the reply.

 

I've been doing more searching and found the FAQ page - it helped A LOT.  Tons of useful info there.

 

With regards to your reply to #6.  Here is the description from the manual..

 

Backup BIOS Image to HDD

Allows the system to copy the BIOS image file to the hard drive. If the system BIOS is corrupted, it will be recovered from this image file. (Default: Disabled)

 

I checked the setting on my board and it is currently set to 'Disabled'.  I know that I've never changed it so it must be true that it's default setting is in fact 'Disabled'.  That said, if the CMOS battery dies then the BIOS would be reset to all Default values and it would not write a BIOS image to any of the HDDs, correct?  The only way this would ever happen is if I changed the setting to Enabled.  So it would seem that I might be ok to use this board without living in constant fear of a dead CMOS battery.

Yes it looks like that BIOS is a good one.  (Gigabyte quickly learned having that "feature" enabled by default lost them a lot of sales.

Also, is the Backup BIOS Image to HDD feature I'm asking about the same as the the HPA issue discussed here that makes some users dub Gigabyte boards as "unRAID poison"?

Yes, it is the feature being discussed in the HPA issue.  The area used to store the BIOS copy is creating by defining a "Host-Protected-Area" (HPA)  This artificially makes the drive look smaller.

 

You'll be fine with that BIOS.

[wsume99]

Great.  Thanks for the help!