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+--- Thread: Unraid "Math" (/showthread.php?tid=124769)
Unraid "Math" - skyking376 - 2012-03-05
Please confirm my understanding of Unraid. Everyone raves about it and I agree with everyone for what I have read so far but I am stuck on the "DATA LOSS" area.
Example:
10 physical drives, 9 for data, 1 for parity (I believe "parity" = backup?)
1) If one drive fails (say #3) the parity drive does fancy things and you have to "rebuild" data when you purchase a replacement drive #3? Yes or No?
2) If two drives fail (say #3 and #7) the parity drive CANNOT help you and you lose data that was on drives #3 and #7, but ALL OTHER drives have their data intact. Yes or No?
3) If PARITY drive fails, you don't have any "backup" so you need to replace ASAP to give you "backup" options. Yes or No?
4) With anybody's experience what is the percentage/average that 2 drives fail in the same day/week? 2%, 10%, 50%, What?
I probably have missed some finer points but however many levels of "safety" I might need it is worth it to NOT have to go through my library again and convert from disc to digital versions.
- harryzimm - 2012-03-05
Hi
Your example is correct.
1)yes
2)yes
3)yes
4)No idea on percentages, I have had drives fail in the past but never more than one at any one time. Thats not to say it can happen.
Hope this helps
cheers
- TapRackPull - 2012-03-05
1.) Yes
2.) Yes
3.) Yes
4.) No idea. I have never had a drive fail. And I don't want one to either. Drives are damn spendy right now.
- TugboatBill - 2012-03-05
The odds are that if you have 2 drives fail at once one of them will be the parity drive. Why? Because it gets the most use as it is updated every time there's a change to any of the drives in the array.
- bumperjeep - 2012-03-05
So if the Parity Drive fails and all other drives are fine, do you lose any data?
- aptalca - 2012-03-05
no.
simply hook up a new drive, set it as parity, let unraid build it as a parity drive
- Orclas - 2012-03-06
I may add that the pro way to buy disks it from different vendors or separate in time, this in order to avoid getting more than one disk from a dodgy batch.
Over the top complication of things for home users? Yeah, probably
- kortina - 2012-03-06
If you are worried about data loss, then buy 1 extra 2Tb drive, and leave it in the packet.
Put this drive into your server as soon as you find a fault.
The risk is when it takes you days to purchase a replacement drive.
In my years of playing with PC's I have never had any drives fail... until I started playing with WD Green drives. They are cheap, and I am begining to think they are nasty. (2 fails, and 4 in more in service)
I will no longer be buying WD Green drives, they get a good review from unRaid users, but I will not put my confidence in them.
- JustinAiken - 2012-03-06
UnRaid's saved me from 3 separate drive failures... I always keep a hot spare precleared so that I can reassign it the moment a drive goes.
Protip: Use a cache drive; it speeds up transfers and reduces disk usage of the others, AND you always have a spare ready to go at a moment's notice. Let's you get some benefits out of the plan-B 2TB you'd have just sitting there otherwise...
- mr.sparkle - 2012-03-06
kortina Wrote:If you are worried about data loss, then buy 1 extra 2Tb drive, and leave it in the packet.
Not quite. Put your extra drive in and preclear it right away. And then just leave it connected as a warm spare. Otherwise, if one goes down (and parity takes its place), you're exposed until the new drive is precleared, during which time another could go down. Unlikely, I know, but still.
- wsume99 - 2012-03-06
You should also consider your purchasing strategy for HDDs because that can influence the likelihood of having simultaneous drive failures. When purchasing HDDs it is recommended that you not buy multiple drives at the same time from the same supplier. If you do they will most likely be from the same production batch and will likely have similar lives. Instead you should stagger your purchases so that the supplier can rotate their stock and you'll get drives from different batches or buy from different vendors if you need to buy multiple drives at the same time.
- Orclas - 2012-03-06
wsume99 Wrote:You should also consider your purchasing strategy for HDDs because that can influence the likelihood of having simultaneous drive failures. When purchasing HDDs it is recommended that you not buy multiple drives at the same time from the same supplier. If you do they will most likely be from the same production batch and will likely have similar lives. Instead you should stagger your purchases so that the supplier can rotate their stock and you'll get drives from different batches or buy from different vendors if you need to buy multiple drives at the same time.
You're too slow on that ball (see post #7)
- wsume99 - 2012-03-07
Orclas Wrote:You're too slow on that ball (see post #7)
Totally missed that one. I really need more sleep.
- Orclas - 2012-03-07
wsume99 Wrote:Totally missed that one. I really need more sleep.
You did explain it in a more precise way though
- Beer40oz - 2012-03-08
Unraid rocks... never had a drive fail. But I had a couple fail at work! totally different story.