Question RAID 01 or RAID 5 with 3 SSDs

May 17, 2021
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Hi

I am planning to do RAID config with :
  1. SSD : 512GB , x2 PCie gen 4
  2. SSD : 512GB, x2 PCie Gen4
  3. M.2 SSD : 1TB, x4 PCie Gen4
Which RAID config is recommended, RAID 01 or RAID5

Will my SSD performance degrade to x2 or will it still work in x4 ?

Please suggest.
 

Rogue Leader

It's a trap!
Moderator
Why?

This has 0 real world benefit other than looking cool in a benchmark, RAID 1 provides no performance benefit, and RAID 5 multiples your risk of data loss.

Aside from the fact you cannot RAID drives of dissimilar size, (the larger drive will shrink), and if you did this you'd be stuck at x2 (not that it matters, again no real world performance benefit).
 
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May 17, 2021
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Why?

This has 0 real world benefit other than looking cool in a benchmark, RAID 1 provides no performance benefit, and RAID 5 multiples your risk of data loss.

Aside from the fact you cannot RAID drives of dissimilar size, (the larger drive will shrink), and if you did this you'd be stuck at x2 (not that it matters, again no real world performance benefit).
I am thinking of having samsung 940 SSD (x4) (1TB)and 2of x2 gen4 SSD soldered down (phison each 512GB) . In RAID 01 i will get 1.5GB total capacity. Will it still operate x2 speed or will it go X4 speed?
 
May 17, 2021
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RAID None.

Dissimilar sizes, a RAID is dictated by the smallest.
Dissimilar speeds, performance is dictated b y the slowest.

And of course, there is rarely a need for a RAID array.
Even less so with SSD's.


What were you wanting this for?
What motherboard is it going on?
What specific drives?
RAID 01 i though will make it work in total x4 mode for read operation and write can be also x4 .........
 

Rogue Leader

It's a trap!
Moderator
I am thinking of having samsung 940 SSD (x4) (1TB)and 2of x2 gen4 SSD soldered down (phison each 512GB) . In RAID 01 i will get 1.5GB total capacity. Will it still operate x2 speed or will it go X4 speed?
It really does not work like that at all. it will always operate at x2 speed first off.

RAID 1 is mirror, it does not combine the size it mirrors the size. (so 2 1tb drives are seen as 1tb). The mirror provides 0 speed improvement, its a barrier against drive hardware failure (which is SO low on SSD's its not worth it).

And what do you mean by soldiered down, you plan to manually move chips and combine them on a single board to make a drive?
 
May 17, 2021
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It really does not work like that at all. it will always operate at x2 speed first off.

RAID 1 is mirror, it does not combine the size it mirrors the size. (so 2 1tb drives are seen as 1tb). The mirror provides 0 speed improvement, its a barrier against drive hardware failure (which is SO low on SSD's its not worth it).

And what do you mean by soldiered down, you plan to manually move chips and combine them on a single board to make a drive?
Sorry i m not getting it .. RAID 01

RAID 0 : of SSD each of x2 (striping)

RAID1 : Mirroring with X4 SSD + RAID0 config.

I think should work to give me bandwidth benefit....
 

USAFRet

Titan
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Mar 16, 2013
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Why will not RAID01 not work in X4:

SSD1(x2) + SSD2 (x2) -> RAID 0

SSD3 (X4) + RAID0 -> RAID1
The 1 & 2 run at x2 speed.
It does not stack to "x4"

So you have 6x drives.
1TB, 1TB, 1TB, 1TB, 512GB, 512GB

5TB total potential space.

Which ones are going in which array type?
(not that it really makes a difference....this is an absolutely bad idea)
 

Rogue Leader

It's a trap!
Moderator
Typo : 960 PRO

Why will not RAID01 not work in X4:

SSD1(x2) + SSD2 (x2) -> RAID 0

SSD3 (X4) + RAID0 -> RAID1
While nesting RAIDs does work, x2 +x2 does not equal x4, that is a physical hardware limitation.

You will be making an incredibly complex setup that will provide no performance benefit over your fastest drive, but an easy way to ruin your data in the case of a crash.

This is an astronomically bad idea.
 
May 17, 2021
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The 1 & 2 run at x2 speed.
It does not stack to "x4"

So you have 6x drives.
1TB, 1TB, 1TB, 1TB, 512GB, 512GB

5TB total potential space.

Which ones are going in which array type?
(not that it really makes a difference....this is an absolutely bad idea)
I have only 3 drives
1) 512GB (x2 pcie)
  1. 512GB (x2 PCie)
  2. 1TB (x4 Pcie)
Which RAID config will give me bandwidth of x4 Pcie ?
 

Rogue Leader

It's a trap!
Moderator
I have only 3 drives
1) 512GB (x2 pcie)
  1. 512GB (x2 PCie)
  2. 1TB (x4 Pcie)
Which RAID config will give me bandwidth of x4 Pcie ?
None. NO RAID CONFIG will do that.

Per all earlier posts there is no way to combine bandwidth, you are limited by your slowest piece of hardware, in this case the x2 drives.

Also RAID 0+1 requires 4 drives when configuring. This won't even work.
 

USAFRet

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OK...all that x2/x4 business was messing me up.

512GB + 512GB + 1TB
2TB potential space.

512+512+RAID 0 = 1TB
RAID 1 mirror with the single 1TB

So now you have 1TB actual space.
Literally throwing out 50% of your drive space.

For...ZERO user facing performance gain, increased complexity, increased fail potential.
 
May 17, 2021
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OK...all that x2/x4 business was messing me up.

512GB + 512GB + 1TB
2TB potential space.

512+512+RAID 0 = 1TB
RAID 1 mirror with the single 1TB

So now you have 1TB actual space.
Literally throwing out 50% of your drive space.

For...ZERO user facing performance gain, increased complexity, increased fail potential.

With RAID 01 i should be getting 1.5TB of total drive rite?

RAID 0 -> 512GB (x2 pcie) + 512GB x2 Pcie) -> 1TB and x4 of pcie gen speed
Then RAID 1 on top of it : 1TB (3rd drive) (x4 pcie gen4) + RAID 0 (1TB) : 1.5TB
 

USAFRet

Titan
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With RAID 01 i should be getting 1.5TB of total drive rite?

RAID 0 -> 512GB (x2 pcie) + 512GB x2 Pcie) -> 1TB and x4 of pcie gen speed
Then RAID 1 on top of it : 1TB (3rd drive) (x4 pcie gen4) + RAID 0 (1TB) : 1.5TB
No.
The 512GB drives in a RAID 0 give you a 1TB array size.
Mirror that to the 1TB in a RAID 1 gives you....1TB total array size.

And again, the x2 drives in a RAID 0 does NOT make it x4. It does not stack like that.

Overall, this monstrosity may be slower than each drive individually.
 
May 17, 2021
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No.
The 512GB drives in a RAID 0 give you a 1TB array size.
Mirror that to the 1TB in a RAID 1 gives you....1TB total array size.

And again, the x2 drives in a RAID 0 does NOT make it x4. It does not stack like that.

Overall, this monstrosity may be slower than each drive individually.
ok

What about RAID 5 config using it here?
 
May 17, 2021
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If i use a pcie switch (1x 4 to 2x2) to connect to two SSDs, will it help in RAID 01?

  1. 1x4 -> Switch(PI3BS1622) -> x2 to SSD2 and x2 to SSD2 (RAID0)
  2. 1x4 -> x4 SSD
RAID 1 between 1 and 2
 

Rogue Leader

It's a trap!
Moderator
If i use a pcie switch (1x 4 to 2x2) to connect to two SSDs, will it help in RAID 01?

  1. 1x4 -> Switch(PI3BS1622) -> x2 to SSD2 and x2 to SSD2 (RAID0)
  2. 1x4 -> x4 SSD
RAID 1 between 1 and 2
Thats not how a PCIe Switch works. And oh my god the amount of money you are trying again to spend FOR WHAT?

You cannot make the drive hardware run at a faster bandwidth than its rating, period.

And again RAID 01 requires 4 drives to configure.
 

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