New Unraid Build

[smino]

Folks I am building my second system, with the latest code.

My plan is to use ARC-1222 PCIe and raid 1 the parity drive.

My question is, once I am up and running, is there anything that needs to happen if I migrate over only a few disks of the old array that was running 4.6? I expect to have to recreate the the shares, but moving over a sata drive, will it simply see the data, or is there some vodoo I need to do?

[JonathanM]

If you establish parity first, every drive you bring over unraid will want to clear and format before it will add it to the array. The way I see it you have two options.

1. Don't set parity, just bring all your drives over and assign them to data slots, then add parity and recalc from there.

2. Set parity and new data drives, bring over old drives and assign them to the cache slot one by one, and invoke the mover to get your data into the protected array.

If you just add data drives to a running array, you will have to invalidate parity by setting a new config and recalc every time you bring over a drive with existing data.

[dikkiedirk]

Folks I am building my second system, with the latest code.

My plan is to use ARC-1222 PCIe and raid 1 the parity drive.

My question is, once I am up and running, is there anything that needs to happen if I migrate over only a few disks of the old array that was running 4.6? I expect to have to recreate the the shares, but moving over a sata drive, will it simply see the data, or is there some vodoo I need to do?

 

Why raid1 the parity? There is no real benefit in that. Do you need redundacy or speed? raid0 seems more logical.

[sureguy]

Folks I am building my second system, with the latest code.

My plan is to use ARC-1222 PCIe and raid 1 the parity drive.

My question is, once I am up and running, is there anything that needs to happen if I migrate over only a few disks of the old array that was running 4.6? I expect to have to recreate the the shares, but moving over a sata drive, will it simply see the data, or is there some vodoo I need to do?

 

Why raid1 the parity? There is no real benefit in that. Do you need redundacy or speed? raid0 seems more logical.

 

Assuming 2 drive failures occur at the same time, and one of them is the parity drive, there would be some benefit.  RAID 0 on the parity drive increases the likelihood of having a multiple drive failure that will result in not being able to rebuild from parity.

[JonathanM]

Assuming 2 drive failures occur at the same time, and one of them is the parity drive, there would be some benefit.  RAID 0 on the parity drive increases the likelihood of having a multiple drive failure that will result in not being able to rebuild from parity.

Rather large assumption. The parity drive is the least important from a 2 drive failure standpoint, as it has no data. If you lose 2 drives and both are data drives, you just lost 2 drives worth of data. If you lose 2 drives and 1 is parity, you only lost 1 data drive. You would be better served by using the extra drive as an extra copy of critical data, as a backup in another location, not a member of the raid array.

 

Raid is not backup.

[sureguy]

 

Rather large assumption. The parity drive is the least important from a 2 drive failure standpoint, as it has no data. If you lose 2 drives and both are data drives, you just lost 2 drives worth of data. If you lose 2 drives and 1 is parity, you only lost 1 data drive. You would be better served by using the extra drive as an extra copy of critical data, as a backup in another location, not a member of the raid array.

 

Raid is not backup.

 

I agree that backing up to a different disk as a better solution - the disk should not be attached to the unRAID box, and really should be offsite.  But running 2 parity disks in RAID 0 mathematically leads to greater risk of data loss.  In your scenario where you lose a parity drive and data drive, if the parity drives were in RAID1 they wouldn't lose anything, but if they use RAID0 they lose the data disk.