build out of a server advice

Mike Lovell mike at dev-zero.net
Mon Jun 25 00:39:13 MDT 2012


On 06/22/2012 03:09 PM, Merrill Oveson wrote:
> Building a server:
>
> one 1 TB - for the OS and programs.
>
> four 3 TB raid 5 - which should give me 9 TB usable.  Correct?
>
> How reliable are the 3 TB drives these days?  Am I taking a big risk here?
>
> thoughts?

correct, you'd have ~9TB usable. i have a 4 drive raid-5 with hitachi 
3TB drives (HDS5C3030ALA630)that have been doing just fine. i just 
checked SMART data on the drives and there haven't been any errors that 
it reports and they all have about 5400 hours of power on time. they are 
in a box that doesn't get a whole lot of i/o traffic but they've been 
doing good for what they're meant for. i did buy 5 drives when i first 
build this array and didn't use 1 in the array cause it was making a 
noise the others weren't but its been in use in a desktop and no 
problems with it either. the drives i have are 'consumer' 'green' drives 
but there are 'enterprise' grade 3TB disks out there. so i wouldn't 
worry too much about the reliability just on the basis of size.

as for the debate on the list about what raid level to use, i think it 
depends on multiple factors. how much activity are the disks going to be 
seeing? how much space is needed? etc. if you don't anticipate a lot of 
disk i/o, then you would probably be just fine with a raid 5. the 
concern expressed in the thread is that you need to rebuild before a 
second failure and that can take a while with large disks. if the disks 
are really busy, it could easily take days to weeks to rebuild. but if 
there isn't, the rebuild can complete in a matter of hours. iirc, a 
rebuild on my 4 drive raid 5 takes about 7 hours which isn't bad for my 
case. if you don't need the max amount of space available, i would 
probably do a raid 10 since it is much less computationally intense than 
a raid 5 or 6. imo raid 6 with just 4 drives is kind of a waste. so it 
depends a bit on what the array is going to be used for.

mike


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