Fastline
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- Joined
- Jul 7, 2023
- Messages
- 358
So @Etorix after researching for a bit, here's what i can conclude
1. The normal SATA III is capable of 6Gb/s which means 600MB/s. HDDs can go up to 300MB/s maxed out (enterprise). For instance, the Seagate X18 can go up to 270MB/s as per the datasheet and it goes like 272MB/s in TrueNAS and up to 289-300MB/s in Windows.
Here, we can see that the bandwidth required for running the HDD at full speed will be like 300MB/s or 3Gb/s approx.
The LSI 9400-16i has 4 SAS ports which can be turned into 16 SATA ports, (4 SATA breakouts from each SAS port).
So, that means 4xSATA on each SAS port would require @300MB/s or 3Gb/s will require 1200MB/s or 12Gb/s per SAS port.
Now that we know that one single HDD will require 300MB/s or 3Gb/s, that means 4xSATA on one SAS port will require 1200MB/s or 12Gb/s. Therefore, 4xSATA on each SAS port would require a total bandwidth of 48Gb/s.
Now, as the HBA can push max 48Gb/s only (12Gb/s per SAS port), one can only install up to 16 HDDs
So, for my use case, 16x300MB/s = 4800MB/s or 48Gb/s approx which is just the maxed out performance out of LSI 9400-16i HBA. I left some extra reserved bandwidth as nothing is 100% efficient, plus it's still 272MB/s so 28MB/s left out to maintain the speed when at peak load.
2. Considering a normal SATA SSD which is capable of 500-600MB/s approx. For instance, the Intel S4610 can go up to 560MB/s Read and 510MB/s Write as per the datasheet, we can conclude the following.
Here, we can see that the bandwidth required for running the SSD at full speed will be like 600MB/s or 6Gb/s approx.
The LSI 9400-16i has 4 SAS ports which can be turned into 16 SATA ports, (4 SATA breakouts from each SAS port).
So, that means 4xSATA on each SAS port would require @600MB/s or 6Gb/s will require 2400MB/s or 24Gb/s per SAS port.
Now that we know that one single SSD will require 600MB/s or 6Gb/s, that means 4xSATA on one SAS port will require 2400MB/s or 24Gb/s. Therefore, 4xSATA on each SAS port would require a total bandwidth of 96Gb/s.
Now, as the HBA can push max 48Gb/s only (12Gb/s per SAS port), one can only install up to 8 SSDs. Just half of the HDDs in numbers.
So, for my use case, 8x600MB/s = 4800MB/s or 48Gb/s approx which is just the maxed out performance out of LSI 9400-16i HBA. I left some extra reserved bandwidth as nothing is 100% efficient, plus it's still 560MB/s-510MB/s so a few left out to maintain the speed when at peak load.
The above calculation sounds fair to me, stated that per SAS port is 12Gb/s. But if the whole HBA Card is just 12Gb/s or say all 4 SAS ports combining a total bandwidth of 12Gb/s, the max i can go for is 4 SATA HDD, which i doubt. Because, its hard to digest that an Intel/AMD PCH board can have like 6-12 SATA in the enterprise segment (sometimes in consumer segment too) and each offers 6Gb/s per SATA port and how could a HBA which is dedicated for such function, offers way much less than that?
Let me know if the math is correct now :)
1. The normal SATA III is capable of 6Gb/s which means 600MB/s. HDDs can go up to 300MB/s maxed out (enterprise). For instance, the Seagate X18 can go up to 270MB/s as per the datasheet and it goes like 272MB/s in TrueNAS and up to 289-300MB/s in Windows.
Here, we can see that the bandwidth required for running the HDD at full speed will be like 300MB/s or 3Gb/s approx.
The LSI 9400-16i has 4 SAS ports which can be turned into 16 SATA ports, (4 SATA breakouts from each SAS port).
So, that means 4xSATA on each SAS port would require @300MB/s or 3Gb/s will require 1200MB/s or 12Gb/s per SAS port.
Now that we know that one single HDD will require 300MB/s or 3Gb/s, that means 4xSATA on one SAS port will require 1200MB/s or 12Gb/s. Therefore, 4xSATA on each SAS port would require a total bandwidth of 48Gb/s.
Now, as the HBA can push max 48Gb/s only (12Gb/s per SAS port), one can only install up to 16 HDDs
So, for my use case, 16x300MB/s = 4800MB/s or 48Gb/s approx which is just the maxed out performance out of LSI 9400-16i HBA. I left some extra reserved bandwidth as nothing is 100% efficient, plus it's still 272MB/s so 28MB/s left out to maintain the speed when at peak load.
2. Considering a normal SATA SSD which is capable of 500-600MB/s approx. For instance, the Intel S4610 can go up to 560MB/s Read and 510MB/s Write as per the datasheet, we can conclude the following.
Here, we can see that the bandwidth required for running the SSD at full speed will be like 600MB/s or 6Gb/s approx.
The LSI 9400-16i has 4 SAS ports which can be turned into 16 SATA ports, (4 SATA breakouts from each SAS port).
So, that means 4xSATA on each SAS port would require @600MB/s or 6Gb/s will require 2400MB/s or 24Gb/s per SAS port.
Now that we know that one single SSD will require 600MB/s or 6Gb/s, that means 4xSATA on one SAS port will require 2400MB/s or 24Gb/s. Therefore, 4xSATA on each SAS port would require a total bandwidth of 96Gb/s.
Now, as the HBA can push max 48Gb/s only (12Gb/s per SAS port), one can only install up to 8 SSDs. Just half of the HDDs in numbers.
So, for my use case, 8x600MB/s = 4800MB/s or 48Gb/s approx which is just the maxed out performance out of LSI 9400-16i HBA. I left some extra reserved bandwidth as nothing is 100% efficient, plus it's still 560MB/s-510MB/s so a few left out to maintain the speed when at peak load.
The above calculation sounds fair to me, stated that per SAS port is 12Gb/s. But if the whole HBA Card is just 12Gb/s or say all 4 SAS ports combining a total bandwidth of 12Gb/s, the max i can go for is 4 SATA HDD, which i doubt. Because, its hard to digest that an Intel/AMD PCH board can have like 6-12 SATA in the enterprise segment (sometimes in consumer segment too) and each offers 6Gb/s per SATA port and how could a HBA which is dedicated for such function, offers way much less than that?
Let me know if the math is correct now :)