stripe size for M.2 raid array?

[captainthrall]

How large of a stripe size should I use for an M.2 raid 0 setup?
What are the pros and cons of using larger or smaller stripe sizes?

I'm using 2x Samsung 950 pros.

 

[Silver_Pharaoh]

How large of a stripe size should I use for an M.2 raid 0 setup?
What are the pros and cons of using larger or smaller stripe sizes?

I'm using 2x Samsung 950 pros.

Depends on how big the average file size is that you will be placing on said array.

128Kb is what I've always used. There is a formula to calculate the average files size. IIRC it's sum of all file size / total number of files.


Others who run RAID and use it daily will be able to give a better explanation and answer

 

[Mpegger]

If I'm not mistaken, SSDs are normally 4kB sized cells. Any multiple of 4kB would work, though being SSD, keeping it at the smallest setting you can use with your controller would be best. Less waste of space, and less garbage collection needed (TRIM) to be done on the SSD.

 

[Woomack]

It depends from RAID purposes. Generally between 64 and 256kb ( 256 more for databases etc ). Controllers usually recommend 64kb or 128kb and this will be default. When you start setting RAID then pick default value and it should set optimal size.

 

[Mpegger]

Doesn't the usual best practices for RAID stripes go out the window when SSDs are involved? You no longer have the problems of dealing with random access speeds or fragmentation, but you do have the problem of TRIM cycles that HDDs don't deal with, including when writing to cells. Why erase and write to 24 cells when 2 cells is enough?

 

[don256us]

Doesn't the usual best practices for RAID stripes go out the window when SSDs are involved?

I don't think so.

I put my SSD RAID 0 at 128 which was the middle of the options that I had available. For me the idea was to get the best performance for both large and small files that I access for my OS and programs.

 

[captainthrall]

Yeah, I may be wrong, but I believe larger stripe sizes increase performance to some point of diminishing returns.

I'm not sure though and would like further clarification.

 

[Silver_Pharaoh]

Yeah, I may be wrong, but I believe larger stripe sizes increase performance to some point of diminishing returns.

I'm not sure though and would like further clarification.

IF you only have large files yes.

If you put an OS on a 4Mb stripe, it won't be as fast as putting it on a 128Kb strip.
That's what I have learned. That's why it's important to pick the correct stripe size, though 128Kb is good for most people.

 

[EarthDog]

Default. For your uses, you wouldn't notice if you had a regular ssd or these 2 smoking for fast drives in R0... nonetheless having a tweaked stripe size for your uses.

 

[Mpegger]

I knew I would find it again.

http://www.overclock.net/t/1535527/...ing-different-drives-vs-same-drive-benchmarks

This is basically what I was trying to say in my post. Stripe size with SSD in RAID 0 is basically a non-factor because SSDs are not HDDs. They don't have problems with access times, or read/write speeds, or fragmentation that mechanical hard drives have. Stripe size was important for HDDs because of those issues.

But stripe size would affect SSDs negatively the larger you go because of wasted space and garbage collection (TRIM cycles, including those when needing to write to a cell that already has data on it). It's best to size the stripe for the smallest file size you would have, which if you are using it as a boot drive, would mean 8kB, to align with the 4kB cell size on a SSD.

And speaking about alignment, that's a whole other issue which I don't know about in regards to RAID. Upon installing a modern OS on a SSD that is SSD aware, when formatting and partitioning, the OS can align the partition correctly. But this may be a issue where the user would have to somehow manually align partitions on the SSDs when in a RAID setup, as the RAID controller/driver may not align the partitions. This could lead to even more wear and tear on the SSD.

 

[captainthrall]

I knew I would find it again.

http://www.overclock.net/t/1535527/...ing-different-drives-vs-same-drive-benchmarks

This is basically what I was trying to say in my post. Stripe size with SSD in RAID 0 is basically a non-factor because SSDs are not HDDs. They don't have problems with access times, or read/write speeds, or fragmentation that mechanical hard drives have. Stripe size was important for HDDs because of those issues.

But stripe size would affect SSDs negatively the larger you go because of wasted space and garbage collection (TRIM cycles, including those when needing to write to a cell that already has data on it). It's best to size the stripe for the smallest file size you would have, which if you are using it as a boot drive, would mean 8kB, to align with the 4kB cell size on a SSD.

And speaking about alignment, that's a whole other issue which I don't know about in regards to RAID. Upon installing a modern OS on a SSD that is SSD aware, when formatting and partitioning, the OS can align the partition correctly. But this may be a issue where the user would have to somehow manually align partitions on the SSDs when in a RAID setup, as the RAID controller/driver may not align the partitions. This could lead to even more wear and tear on the SSD.

Thank you sir. This was extremely useful. Not only was the data presented in a perfectly organized manner to emphasize the important features, the follow-up analysis explained the phenomena that were apparent in the data trends. That cheeseandcereal guy is one smart cookie. Fantastic information!

I've decided to go with a 16kb stripe size, as should anyone else with a RAID-0 SSD array (unless they only have a tiny amount of maximum storage space and anticipate exclusively using extremely small file sizes) Good info, thanks again!