Sil3124 + Sil4726 PortMultipier and FreeBSD9

Alexander Motin mav at
Sun Dec 4 15:33:36 UTC 2011

On 04.12.2011 04:46, Nenhum_de_Nos wrote:
> this port multiplier will work ok ? On Sil3124 and which others ?
> the tip on FreeNAS was great, but my main concern here is the sata hardware compatibility. I'd
> like to buy it knowing it will work :)

Port multipliers supported by all siis(4) hardware and many mvs(4) and 
ahci(4). In case of mvs(4) and ahci(4) support and effectiveness depends 
on controller model. SiI3124 is known to be a good option. If 
performance is not the first priority (150MB/s should be enough for home 
NAS) -- SiI3132 and SiI3531 are also fine. 6Gbps Marvell 88SE91xx in 
_non-RAID_ versions also good on tests, but there are not so many 
reports about them yet.

I can't say for sure about ICH7 and NM10, but many Intel chipset 
controllers support port multipliers when AHCI is enabled. I have 
feeling that all of them support it in hardware (at least since ICH8), 
but it is blocked by BIOS. At least I had motherboard that had and lost 
port multipliers support after some BIOS update. You may see that info 
in ahci(4) boot messages. Unluckily now Intel supports only 
command-based switching, that allows only one device beyond port 
multiplier execute commands at a time and significantly limits 
performance. Controller support for more effective FIS-based switching 
reported by ahci(4) and mvs(4) drivers during boot. All siis(4) 
controllers support FIS-based switching.

Also note that not all controller BIOSes support detecting and booting 
from devices on port multiplier, except one on the first port. Consider 
that when choosing controller and partitioning disks if you are going to 
boot from them.

Port multipliers themselves are quite simple from driver point of view, 
so all of them should be supported if they follow standards. At least I 
haven't seen reports yet that some one is not supported. What's about 
reliability comparison -- I have no info.

Alexander Motin

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