2x RAID1 vs 1x RAID10

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Paul1977

4983 posts

Uber Geek

#240112 21-Aug-2018 13:46

I have 4 identical HDDs (4x 4TB WD Black SATA) that I will be installing in my PC, they will be attached to an HP P420 RAID controller with FBWC.

Much of what this PC will be doing is remuxing large video files, so there will be quite a bit of simultaneous reading and writing.

Which will perform better:

A. Two RAID1 arrays, where one array is read from while the other is written to.

B. A single RAID10 where the array is read from and written to at the same time.

Thanks.

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#2076776 21-Aug-2018 13:52

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Dynamic

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#2076842 21-Aug-2018 14:00

I think the difference would be small, and the 'one lump of disk' of the RAID10 would be less hassle..... it would depend a bit on the speed of the processing (number and scale of the effects being applied, resolution, etc) whether the processor is the bottleneck or the RAID/cache/drives.

I'd encourage you to give it a try for yourself on a modest sized file and let us know your results. Blowing away the one RAID and creating another is quick and easy if you have not already filled the drives!

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Paul1977

4983 posts

Uber Geek

#2076844 21-Aug-2018 14:10

Dynamic:

I think the difference would be small, and the 'one lump of disk' of the RAID10 would be less hassle..... it would depend a bit on the speed of the processing (number and scale of the effects being applied, resolution, etc) whether the processor is the bottleneck or the RAID/cache/drives.

I'd encourage you to give it a try for yourself on a modest sized file and let us know your results. Blowing away the one RAID and creating another is quick and easy if you have not already filled the drives!

It's mainly remuxing rather than encoding or re-encoding, so very little processing power required. The (comparatively) slow 7200rpm spindles will almost always be the bottleneck for my usage.

Yeah, might have to just test both options and see if there is enough of a difference worth worrying about.

bagheera

534 posts

Ultimate Geek

#2076850 21-Aug-2018 14:34

Paul1977:

Dynamic:

I think the difference would be small, and the 'one lump of disk' of the RAID10 would be less hassle..... it would depend a bit on the speed of the processing (number and scale of the effects being applied, resolution, etc) whether the processor is the bottleneck or the RAID/cache/drives.

I'd encourage you to give it a try for yourself on a modest sized file and let us know your results. Blowing away the one RAID and creating another is quick and easy if you have not already filled the drives!

It's mainly remuxing rather than encoding or re-encoding, so very little processing power required. The (comparatively) slow 7200rpm spindles will almost always be the bottleneck for my usage.

Yeah, might have to just test both options and see if there is enough of a difference worth worrying about.

I would say 4 drive in raid 10 would be better - write is where you get the bottlenecks, and more disks in a raid help a lot on the iops on writes.

SirHumphreyAppleby

2830 posts

Uber Geek

#2076851 21-Aug-2018 14:34

If you're just remuxing, two independent disks without any level of RAID would likely offer the best performance.

Paul1977

4983 posts

Uber Geek

#2076861 21-Aug-2018 14:54

SirHumphreyAppleby:

If you're just remuxing, two independent disks without any level of RAID would likely offer the best performance.

I want the redundancy though as the disk will also be used for storage.

Paul1977

4983 posts

Uber Geek

#2076862 21-Aug-2018 14:58

bagheera:

I would say 4 drive in raid 10 would be better - write is where you get the bottlenecks, and more disks in a raid help a lot on the iops on writes.

I'm leaning the other way. Certainly the max write speed is better with RAID10, but this will surely be counteracted by it performing an equal number of reads at the same time.

I think testing it will definitely be required!

bagheera

534 posts

Ultimate Geek

#2076868 21-Aug-2018 15:03

Paul1977:

bagheera:

I would say 4 drive in raid 10 would be better - write is where you get the bottlenecks, and more disks in a raid help a lot on the iops on writes.

I'm leaning the other way. Certainly the max write speed is better with RAID10, but this will surely be counteracted by it performing an equal number of reads at the same time.

I think testing it will definitely be required!

for raid 1 or raid 10 the read iops is nx, write is 0.5nx where n = number of drives, x is ipos of drive so for 2 x raid 1 read iops is 2x your write iops is x, for a raid 10 your read iops is 4x, your write iops is 2x - over all with reading and writing raid 10 will be better for raid 10. 50/50 blend read / write = (RIOPS * .5) + (WIOPS * .5) so (4*.5)+(2*.5) = 3x vs write raid 1 of x

SirHumphreyAppleby

2830 posts

Uber Geek

#2076873 21-Aug-2018 15:12

Paul1977:

SirHumphreyAppleby:

If you're just remuxing, two independent disks without any level of RAID would likely offer the best performance.

I want the redundancy though as the disk will also be used for storage.

I think more details of your workflow is required to work out the best solution. E.g. do you remux in one or two steps, and do you intend to keep the original and remuxed files, or any of the intermediary data, and how much data?

I recently remuxed approximately 15TB of video. I did it all as batch jobs, with the source and output stored on a NAS (RAID6), and intermediary files destroyed. The actual remuxing was done on a PCI-E SSD, where read/write wasn't an issue (warranty aside - that's 20% of the drives guaranteed write life gone in about a week), but if I had to use mechanical drives, I would split the source and destination where possible. Obviously, this was a lot slower than doing it with local storage (or even installing software on the NAS), but in my case the time taken didn't matter that much. It may be more important in your case.

gbwelly

1238 posts

Uber Geek

#2076964 21-Aug-2018 17:06

Paul1977:

I think testing it will definitely be required!

I wouldn't bother. As re-muxing is basically a simultaneous multi GB sequential read and write it's a no brainer. Two raid 1 volumes makes for 1 seek for the read volume and 1 for the write volume, and it's like a fire hose from there on in.

Paul1977

4983 posts

Uber Geek

#2077077 21-Aug-2018 20:25

Well, Tested and found the following:

RAID10 writing 320 MB/s

RAID10 reading 320 MB/s

RAID10 simultaneous reading and writing 120MB/s

RAID1 reading 160 MB/s

RAID1 writing 160 MB/s

I tested the max read and write speeds by copying to and from my existing RAID5 array.

Interestingly even when copying a large file off the RAID1 onto the faster existing RAID5 the read speed still topped out around 160 MB/s - I had been expecting the read speed of RAID1 one to be higher than the write speed, but this was not the case.

Now I think I need to do as @SirHumphreyAppleby suggests and think about my workflow. 2x RAID1 certainly makes the work on the new array(s) faster than 1x RAID10, but 1xRAID10 makes moving data on and off the new array(s) twice as fast as 2x RAID1.

Paul1977

4983 posts

Uber Geek

#2077078 21-Aug-2018 20:30

gbwelly:

Paul1977:

I think testing it will definitely be required!

I wouldn't bother. As re-muxing is basically a simultaneous multi GB sequential read and write it's a no brainer. Two raid 1 volumes makes for 1 seek for the read volume and 1 for the write volume, and it's like a fire hose from there on in.

Turns out you are correct. But the more I think about how this will fit in with the rest of my setup I suspect RAID10 might actually prove better overall.

solutionz

589 posts

Ultimate Geek
Inactive user

#2077312 22-Aug-2018 11:41

If it's only short term processing have you considered RAID-0 ?

Paul1977

4983 posts

Uber Geek

#2077522 22-Aug-2018 15:36

solutionz: If it's only short term processing have you considered RAID-0 ?

I still want to have it redundancy.

Paul1977

4983 posts

Uber Geek

#2077536 22-Aug-2018 15:51

I just had a very interesting and unexpected result.

I put the 4 drives in single RAID5 and am getting comparable max read and write performance as with RAID10, but the really surprising part is I am actually getting better simultaneous read/write performance than either 1x RAID10 or 2x RAID1.

When doing a simultaneous read/write (as in remuxing from and to the same array) the speed fluctuates up and down a lot with RAID5, but is averaging about 195 MB/s (compared to steady 160MB/s between 2x RAID1 and a steady 120MB/s on 1x RAID10)

And RAID5 gives me 50% more usable space.

My only conclusion is that the parity generation on the P420 is VERY FAST, combined with the data being striped across more disks.

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