Date: Sun, 16 Nov 2014 17:26:19 -0700 From: Brandon Vincent <Brandon.Vincent@asu.edu> To: FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: OT-ish SATA port replicators vs. SAS "expanders" Message-ID: <CAJm4238NDHV_uzertrrcce9kwFwyKoYY6pO5E58s-2DoZkwm-w@mail.gmail.com> In-Reply-To: <54693866.9040009@sentex.net> References: <CACpH0Me7Y%2Bm6cENsg2otcP9agDp%2BwKPGnPxDafFfySPNkhsKBA@mail.gmail.com> <CAJm423_%2B5wL4G48ftVOmmkyyjSpekS3=sv801pyquRkqcz=fTQ@mail.gmail.com> <CACpH0MdfzpTXceHnRkAo60ztu4Bo%2BbKSpOYZJyV6goY0Q0TbUg@mail.gmail.com> <54693866.9040009@sentex.net>
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On Sun, Nov 16, 2014 at 4:51 PM, Mike Tancsa <mike@sentex.net> wrote: > I don think a port multiplier is the same as a SAS expander and a SAS/SATA > controller does not necessarily support port multipliers. You're absolutely correct. The SATA specifications if I recall correctly, outline that providing support for port multipliers is optional. Not to mention, the vast majority of chipsets that do have support for port multipliers only provide the slower command-based switching method [1], The LSI SAS 2008 chipset is not what you typically find on the cheap consumer "fake RAID" cards which most people have [2]. Most people who purchase this card are purchasing it for SAS, true RAID, performance, and reliability. Thus, LSI is only going to provide support for the far superior SAS expander technology. Brandon Vincent [1] https://www.sata-io.org/port-multipliers [2] http://en.wikipedia.org/wiki/RAID#Firmware.2Fdriver-based
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