What is best RAID performance for a write intensive implementation

I have inherited a Synology RS815+ with 4 - 6TB hard drives.  The RS815+ is going to be used as a backup only, so it will be write intensive.  My question is what RAID level is the best for this application.  RAID 1 would seem the best for speed and redundancy but would not be the best use of all of the disk space, as I understand it.

If I could have 2 Raid 1's that would be ideal.

Take it easy on the replies, my understanding of Raid is at the beginner level
c7c4c7Asked:
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nociSoftware EngineerCommented:
RAID 1 in general has the best performance with redundancy, when the RAID fails it will actually increase (1 less write to do).

RAID 4/5/6 always need extra I/O  (read old data before replacement)  to recompute the parity.
If you just want speed without any form of redundancy, Raid 0 will deliver that.... and also if one drive fails, the driveset is lost as a whole.
raid 4 has worst performance (Parity disk will be the bottleneck) raid 5 has one parity area, raid 6 has two (so less performance, higher survivability of errors).
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Lee W, MVPTechnology and Business Process AdvisorCommented:
RAID 1 is NOT good for speed.  It's good for redundancy but costly (as half the space is taken up by the redundant copy).  It shouldn't be any slower than a single disk, but it's no faster either especially on writes.

If this is a backup only, then you already have redundancy, right?  In which case, speed is your focus*.  For speed, RAID 0 is best.  BUT, there is ZERO redundancy in a RAID 0.  None.  If any disk fails, all data is lost.  Generally RAID 5 or RAID 6 is good for speed and redundancy.  RAID 5 provides for n-1 of disk space.  Meaning, with 4 (n) drives of 6 TB, you get 18 TB of space (4-1 x 6TB).  RAID 6 has the same net storage waste as RAID 10, RAID 0+1, and two mirrors.  There are many articles explaining what RAID is, I'd suggest reading over them and trying to understand that first.
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Lee W, MVPTechnology and Business Process AdvisorCommented:
I don't know the synology devices, but in more traditional server based RAID configs, the controller plays a HUGE role in performance.  Software RAID is generally MUCH slower than a caching controller on a RAID 5 or 6.
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c7c4c7Author Commented:
Am I correct in assuming that I can have only one Raid array per controller?  In other words I cannot have 4 Raid 0 arrays, in this configuration
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Lee W, MVPTechnology and Business Process AdvisorCommented:
You only have 4 disks, right? You can't have a RAID 0 array of 1 disk.  Did you look up the definitions of RAID?  It seems redundant for us to re-post what's been posted a million times on numerous other web sites.  If you have an issue understanding, then reference the one your using and we can try to clarify - no problem with that...

And it depends on the controller.  Some controllers can't support more than one array (those are usually the poor quality, cheap controllers).
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c7c4c7Author Commented:
If Im bothering you with my questions don't answer anymore

The last 2 sentences are the only thing that addressed my question, thanks for that
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Lee W, MVPTechnology and Business Process AdvisorCommented:
I've provided you answers.  It's up to you take them.
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andyalderCommented:
RAID 10 would be fastest with redundancy but it will cost half your space. If you had more disks then RAID 6 would beat RAID 10 for sequential writes but with only 4 disks there isn't much difference. RAID 5 is too risky with high capacity disks.

A tape drive would beat it for speed  but you don't have one of them.
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Marshal HubsEmail ConsultantCommented:
I agree with andyalder, Raid 10 is definitely one of the best RAID implementation out there since it combines the best of both redundancy and speed as rightly explained in its name RAID 1+0.
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c7c4c7Author Commented:
In the end I went with Raid 10 because of the added redundancy.  Although this is a backup,which is the redundancy,  we decided that we want it to live in case the humans don't notice a problem with a disk.
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