RAID 1 vs Software solution

[commissar_mo]

Despite having read and experimented so much with RAID, I still always have fundamental questions.

Is the only advantage to using RAID 1 over say, using software (like Acronis) to just backup a drive to another one, the fact that RAID 1 is hardware based, and thus won't use (as much) memory in the background as the software?

From what I have experienced, RAID 1 mirror drives are NOT bootable when the main drive fails - the MBR is not properly encoded to make the 'second' drive an exact replica of the original, which means when a RAID 1 breaks (one drive fails) - you still have to replace the dead drive and rebuild before you can boot again - i.e. downtime.

With the software solution, I feel, provided it images lets say weekly, and then does incremental backup on top of the weekly image - when the drive dies, you should immediately be able to go to the backup drive, restore the image, restore the backups over the image... and be back where you started?

I suppose what I'm asking - why RAID 1 when you can use software, which to me on the surface, seems 'better'?

 

[sminlal]

The advantage of RAID 1 is that it can eliminate downtime - if one drive fails the system can continue using the other drive transparently. This is pretty much a requirement for datacentres, but for most home users the downtime and need to restore from a backup is just an inconvenience.

A properly implemented RAID 1 system should be able to boot from either volume of a mirror set. Software-only RAID can't do this because the motherboard BIOS is always set to boot from a particular drive. However chipset-based RAID and add-in RAID controllers can.

However even if you use RAID-1 you still need to do backups, since RAID doesn't protect your files from risks such as deletion, corruption, theft of your system, hardware problems due to common-mode issues such as power hits, etc.

 

[commissar_mo]

Backups - of course. I didn't realize though that hardware RAID would allow booting from either volume. I suppose it's because I already run 2 RAID 10 arrays each on a hardware controller, and I ran out of PCI slots - I've been wary of any RAID that isn't hardware card based since I had problems with the X58 chipset setting up my RAID 0, the drives got unplugged for shipping the case, and when they were plugged back in - probably swapped them, because the RAID was broken... and I had to reanneal it with recovery software. Bad times.

Thank you though! - I'm not worried about downtime with this volume, so I'll probably just rely on backups.

 

[BlueCat57]

I believe I read somewhere that if you have a primary drive failure you need to switch the SATA cable before you can boot from the secondary drive. I wish I could be definitive but I came across that tidbit while researching something else.

Apparently Windows 7 can do software RAID. Again in passing, I read someone suggesting that software is better than a hardware based setup since it is not motherboard or card dependent. If either piece of hardware fails then you do not have potential hardware compatibility issues. However, somewhere else I read that NVIDIA has pledged to keep their hardware RAID compatible and someone related a story that indeed supported that claim.