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Raid 6 or Raid 10 configuration
I have 6 disks of 2TB each. What is the best configuration for backups.
If we do raid 10 or raid 6 with 4 used and 2 hot spare, then how it works if one fail or two fail?
What is recommended.
If we do raid 10 or raid 6 with 4 used and 2 hot spare, then how it works if one fail or two fail?
What is recommended.
ASKER
Ok. So if we do raid 10 with 4 used and 2 spare drive and if one fails will it auto selects one of the spare drive and copy its contents to it? And what if 2 drive fails, will it auto copy its contents to both the spare drives with no data loss?
As long as the data is finished copying before the second drive fails.
Losing 2 drives at the same time is what could cause data loss.
Losing 2 drives at the same time is what could cause data loss.
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ASKER
So should I do Raid 10 with 5 used and 1 spare OR 4 used and 2 spare?
Some of your second question might be contingent on the quality of the RAID controller and management software. I've seen some lower end adapters that only allow one hot spare. I've always been partial to HP ProLiant Smart Arrays but they're not the only quality game in town.
RAID 10 is always an even number, save for any hot spares. Frankly, I'd do 4 drives in the RAID 10 and one hot spare. Then, keep the other in the closet or something. I think have two hot spares in a RAID 10 is a bit of overkill. But, nothing stopping you from doing it save for a cruddy RAID adapter!
Seeing how critical your backup data might be, running without a hot spare (no matter how very resilient RAID 10 is) wouldn't be a "hot" idea!
Raid 10 four drives and one hot spare
Since it's sequential data I would go for RAID6 rather than RAID10, backup files are big enough for the controller to write full stripes so there's no "six IOs for a single write" penalty that you get with random data on RAID 6 so long as you have a reasonable controller with write cache. RAID6 sequential read speed is normally better than RAID10 sequential read as well since there are more disks with usable data on them (read load balancing never works very well with RAID10). I'd do 6 or 7 disks in RAID6 plus one spare.
The newly added drive simply has to copy its contents to the replacement drive, rather than doing all of the calculations to rebuild the RAID array.
It's during the rebuild time where you are the most vulnerable and if a drive fails during the rebuild, you have to re-build the array and restore from backup.