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linux raid 10 ssd onboard sata bandwidth

M

mercnz

n00b
Joined
Jul 11, 2013
Messages
18
so i'm thinking of doing raid 10 on onboard sata ports on a b85 chipset board, it has 4x6gbps, and 2x3gbps ports.

my current thinking is that i should be able to max out my 4x pci-e infiniband ddr connection port with just 3 120gb ssd's for reads at least. but i was reading there's bandwidth limitations on intel pch that should limit to 2GB/sec, which is what i'm at with 4x pci-e as well, but can only push 1400MB/sec. i know i can swap the video card and infiniband card around to raise infiniband back to around 1600MB/sec, but i'm wondering if raid is going to hit the same limitation, and whether or not i should be thinking about 4x120gb ssd's to max out 1400MB/sec. in a way using 3 ports, means i can do 3x hard-drives further down the track if i want to at the same time. the idea would be to use the linux "far=2" option which means that all drives are read from at the expense of slower writes (although I dunno how much slower writes will be if using ssd's), and linux's software raid seems to be the only easy way to raid 10 on 3 drives. i'm also wondering idlely if running at peak speeds will impact anything else negatively. i imagine the same bandwidth is shared with usb, ethernet, but i don't think that should matter. i can't add a pci-e sas controller for more bandwidth, as it's a microatx board with only 2 pci-e x16 one with the x8 infiniband card, and one with the x16 video card. and the second pci-e x16 slot only runs at x4.

and this is a haswell board, but it looks like bandwidth hasn't increased since sandy bridge.
 
The question is, why do you want to do RAID 10, and why are you trying to do it on 3 drives?
 
Tsumi said:
The question is, why do you want to do RAID 10, and why are you trying to do it on 3 drives?
Click to expand...

so i can max out infiniband basically. i don't really /need/ to, but at the same time, raid 1 on two 120gb ssd's would only give me 120gb of storage, and raid 10 on 3 would give me 180gb which would be less borderline. i initially thought of having raid 10 on part and raid 5 on part. 3 drives, well, if i want 3 disk hard-disk pool later it's easier. 3 disk is cheaper than 4 disk. in the future i'm more likely to want to upgrade to newer 250gb ssd's, but 120gb ssd's should still be useful for various things so it not completely wasteful.
 
I would just use a single 250GB drive. That is unless your load is going to be a lot of very large files or you have a situation where the queue depth will be high.
 
drescherjm said:
I would just use a single 250GB drive. That is unless your load is going to be a lot of very large files or you have a situation where the queue depth will be high.
Click to expand...

that's what i'm doing atm. but i upgraded from a 128gb ssd that died which makes me a little edgy. i figure that i'll stick the 250gb ssd into my other computer which currently has 120gb ssd. then do reinstall with 3x120gb ssd, and do uefi at the same time.

i do realise that i could prob get similar performance increase by shifting to 32gb of ram. but ssd would give higher minimum performance.
 
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