25S22M2NGFFR, SAS and JBOD Mode

looking to understand JBOD mode and SAS to how it works compared to a STAT port multiplier.

in my understanding of the SAS/SATA protocol, a SATA port multiplier aware port is the same as as a SAS Expander. so if I have an external enclosure with a SAS Expander, should I not see both drives in JBOD mode of the 25S22M2NGFFR, doubling the drive density? Though unlike a port multiplier SATA setup, SAS expanders don’t share the total bus bandwith, each port has a full speed SAS lane.

to make sure I understand the difference, a SAS Expander enclosure is not the same as a SAS JBOD enclosure. the SAS JBOD enclosure is basically the equivalent an external fan out cable (mini-SAS SFF-8087 → SATA connector) with a back plane, or having 8 non-port multiplier aware SATA ports?

Another question related to Fan-Out cables, if I use a internal fan out cable (mini-SAS SFF-8087 → SATA) from an expander, would this not also work, as it’s basically what a SATA port multiplier is doing? just on a SAS bus?

on non SATA port multiplier aware ports, I’m able to see both M.2 drives, though not at the same time, so I know at least im able to address both M.2 drives, once I have the right way to address both in JBOD mode.

Hello @RamenNoodles,

Thank you for taking the time to post on the Startech.com Community!

To use 25S22M2NGFFR in JBOD mode, it is intended to be connected to a SATA controller that supports Port Multiplier. Unfortunately we have not tested it with a SAS enclosure or controller that uses SAS Expander, so we are unable to confirm if this is something that would be expected to work or not. It would be best to contact the manufacturer of your enclosure with SAS Expander to confirm with them if it supports Port Multiplier when connecting to a SATA enclosure such as our 25S22M2NGFFR that has multiple drives inside.

I apologize we are not able to give a more definitive answer on if this would work.

With regards to a fan out cable that you are describing, that would go from one mini-SAS connector to multiple SATA connectors, I would not expect that to work with a device like 25S22M2NGFFR in JBOD mode. The fan out cable is essentially already doing the work of Port Multiplier but it is splitting the signal on a physical level, expecting a single drive to be connected to each SATA connector. The Port Multiplier functionality would already be taken up by the cable itself then be unable to then secondarily use Port Multiplier again down the connection to detect multiple drives in 25S22M2NGFFR.

Lukas T

looking how port multiplying works, seem it’s a swtiching protocol spesfic to SATA and comes in 2 flavors

command-based switching or FIS (Frame Information Structure)-based switching

These are not supported by SAS. so the HBA needs to support it and there seems to really be only one chipset/HBA series that supports one of the 2 switching protocols - FIS

and these cards seem to have that chipset

SAS 9305-24i
SAS 9305-16i
SAS 9305-16e

does the 25S22M2NGFFR play nicely with FIS?

it seems to support FIS, a confirmation of my understanding would be appreciated.

your tech specs: Chipset ID ASMedia - ASM1092R

support for: SATA II: Port Multiplier Specification Revision 1.1

Spec reference: https://www.intel.com/content/dam/www/public/us/en/documents/technical-specifications/serial-ata-ahci-spec-rev1_1.pdf

FIS-based Switching Supported (FBSS): When set to ‘1’, indicates that the HBA
supports Port Multiplier FIS-based switching. When cleared to ‘0’, indicates that the
HBA does not support FIS-based switching. AHCI 1.0 and 1.1 HBAs shall have this bit
cleared to ‘0

so at this point, it seems it should be good to support the SAS RAID cards I reference

this HBA uses the same chipset as your drive, and according to the product specs, it supports 3 switching protocols, just depends what bits the 25S22M2NGFFR exposes


the SATA controller. Supports Message Signaled Interrupt (MSI). Supports Port Multiplier FIS based switching or Command based switching.


could you confirm the details I posted about the chip set in the 25S22M2NGFFR and support for FIS?

Hello @RamenNoodles,

I apologize for not being able to reply sooner.

Unfortunately I do not have a confirmation if 25S22M2NGFFR supports FIS based switching available on hand and will need to look into this further to see if we are able to confirm this for you.

To help us better understand your setup and look into this for you, can I please ask the model of the SAS enclosure you are trying to use our 25S22M2NGFFR with or are you using one of the SAS chipsets you had mentioned?

I also want to ensure I correctly understand what it is you are trying to do. Are you wanting to us 25S22M2NGFFR inside of your SAS enclosure in JBOD mode so that both drives in 25S22M2NGFFR are detected independently while only taking up a single physical slot in your enclosure? If I have misunderstood what you are trying to do, I apologize and please correct me.

Lukas T



it’s a standard JBOD with simply a SAS backplane, no expander inside. Can look at this as Mini-SAS SFF-8087 → SAS fan out cable (our Mini-SAS SFF-8087 → SATA fanout) as I’ll either put the 25S22M2NGFFR in the external JBOD enclosure or on a fan out cable inside.

to help, the enclosure and expander really have no say in the switching protocol support, they are signalling switches or back planes to connect stuff to and route the commands correctly, all of this seems to be in the HBA/controller itself.

in your world connect the 25S22M2NGFFR (Asmedia ASM1092R) to the ST521PMINT (JMicron - JMB575A) and achieve:

with the 25S22M2NGFFR in JBOD mode.

my end setup is going to connect the 25S22M2NGFFR to the LSI SAS 9305-16i listed earlier directly, via SATA Fanout cable or external JBOD enclosure, or via an HPE 727250-B21 12Gb SAS Expander Card + SATA fanout cable. if connecting the 25S22M2NGFFR to the ST521PMINT works, (looking how the ASM1092/ASM1092R chipset it used in competing devices) it should work with the 25S22M2NGFFR to LSI SAS 9305-16i setup as the LSI SAS 9305-16i has support for FIS. see the 3324 ROC link, that’s the chipset of the LSI SAS 9305-16i (but 3316 ROC for the 16 port version)

Hello @RamenNoodles,

Thank you for the additional details and explanation. This is helpful in getting to understand the full picture of what you are wanting to do.

May I also ask for how many 25S22M2NGFFR you plan to use in your setup and the drive models you will install in the 25S22M2NGFFR for reference?

I will follow up with you as soon as I can regarding the FIS based switching support.

Lukas T

the JBOD enclosure, it has 8 bays, looking to jam 16 M.2 SATA drives in there. if that works, expand to other machines with the same HBA/RAID card. they are 4U servers with existing SAS RAID cards, might just need to swap it if I can physically change the card for the server in question. (hoping its not a custom designed RAID card for the chassis)

should not really matter, all that does is that the M.2 drive supports SATA and not NVME . It could be a no name SATA M.2 from china with really cheap NAND inside. the 25S22M2NGFFR should accept really any SATA M.2, irrespective of brand

Hello @RamenNoodles,

I apologize for the delay in as we looked into this for you and thank you for your patience.

Unfortunately 25S22M2NGFFR does not support FIS-based switching. We apologize for the inconvenience.

Lukas T

much promise
so excite
very disappointed.