technical details - linux compatibility etc.
With respect to Linux, Adaptec's FSA RAID (aacraid) historically has been and still is one of the first and best supported RAID controller brands, on par with maybe only 3ware. The Linux user-space utils starting with aaccli/arcconf and ending with the "Storage Manager" have always been among the best on the market. The vanilla Linux AACRAID driver even exhibits some "forward compatibility" with newer AACRAID cards - detects them as a generic AACRAID model and tends to work with them just fine.
I remember a time at the end of nineties when AACRAID was a novelty, but it soon became a cornerstone of Linux HW RAID driver support. I still remember how happy I was around 2003/2004 that the old DPT RAID flavour of Adaptec cards was finally gone - especially the last specimen of the DPT ZCR family tended to be unreliable and the firmware features were sub-prime.
3ware used to be the cheapest HW RAID, reliable and compatible, but lacking CPU horsepower. From 9000 series above I lost track, so I cannot judge the current portfolio (they finally seem to have switched to high-performance CPU's, the AMCC-flavour PowerPC).
Regarding Adaptec's own SCSI controllers (AHA/ASC/AIC): I started to avoid them with the second generation of AIC-7902/29320/39320, which apparently can be distinguished by the "A" suffix. The first-gen Adaptec U320 controllers had no problem against LSI U320 targets (I still have one or two pieces), but the latter variety couldn't run properly at U320 against LSI, hence there was a problem getting them to work with CDB16/LBA64, which was a problem with external storage boxes, typically featuring target-mode controllers by LSI. Even the earlier variety of U320 *and* 64bit (PCI) U160 controllers had some problem against ServerWorks chipsets (ceased to be a problem as Intel chipsets finally prevailed in servers).
None of this was a problem with the Adaptec RAID controllers, because
A) you don't attach an external RAID box to an internal PCI RAID
B) on ASR2120/2200 the AIC HBA chip is attached to the host PC via a PCI IOP CPU by Intel, hence no problem with PCI compatibility.
Regarding the Adaptec SATA RAID portfolio and "rebadging a SiliconImage chip": many people still fail to distinguish
A.) a proper hardware RAID controller (with its own CPU, RAM and firmware in Flash)
B.) from a "soft RAID" (just a cheap HBA chip with a companion Flash for the BIOS option ROM).
I cannot tell whether or not it was a marketing error on part of Adaptec to sell cheap soft-raids, which admittedly are a problem in Linux. The AAR-1200 series were a soft RAID (HostRaid in Adaptec lingo). The AAR-2410 / 2420 were/are a proper hardware RAID (aacraid family), in terms of features precisely on par with Adaptec 2120/2130. Actually the SATA implementation is even slightly better in some respects, such as independent drive channels and quicker response to drive failures (that's right, the failure response on SCSI is *slower*). When shopping for an Adaptec controller for Linux, you always had to check that you were buying an "aacraid". You always get what you pay for. The SiliconImage chip itself is pretty good in its class, has no obvious compatibility or performance problems - in that sense, it was certainly a good choice. Obviously not for the Linux folks, who don't like being fooled into buying a software RAID stack that they have to dump anyway (if it can be circumvented at all, starting from the BIOS).
Note that there were even SCSI HBA's wearing the "HostRaid" suffix - some members of the 29320/39320 family. Of course those were easier to identify as "just plain HBA's" by the basic product number.
One last note regarding Adaptec HostRaid: among the many "software RAID HBA" implementations out there, the Adaptec HostRaid BIOS and drivers were among the best. As good as it gets, without a dedicted CPU. Adaptec shipped the HostRaid even with onboard HBA's - initially with the SCSI AIC series, later on the stack also started to appear as just a BIOS option ROM with third-party onboard HBA's (Intel ICH, even Marvell I think). E.g. on some SuperMicro motherboards, you have a choice between an original Intel soft-RAID stack (matrix storage) and the Adaptec HostRaid option ROM. To me, the choice has always been clear - the Adaptec HostRaid, owing to its bug-free BIOS part and excellent OS-based management tools. Unfortunately for Adaptec, the onboard HostRaid stack was almost invisible in the motherboards' marketing material (product web, datasheets, packaging), and actually hardly any end-customers knew enough to tell a difference.
Obviously this train of thought is only valid for Windows. Forget about HostRaid for Linux. If you don't want to pay for a genuine HW RAID, save some money, buy a plain HBA and use a native Linux MD RAID. Some argue that the MD RAID even has advantages over a proprietary HW RAID in terms of both performance and "hardware-independent crash recovery".
I still remember the time when Intel rounded off the i960-based generation of the IOP CPU family and all the RAID vendors depending on that (Adaptec and MegaRAID among others) had a hard time taking the next step - some followed the path to Intel Xscale IOP's, others took other paths. Adaptec finally rolled out its own RoC chips, forming the basis of ASR-2130/2230 (MIPS-based?). Adaptec later returned to Intel with the "universal SATA/SAS family" (so the AACRAID firmware once again ran on Intel Xscale hardware), though actually the first Arm-based AACRAID was the old ASR5400 quad-channel SCSI if memory serves...
It may well be that the discontinuation of i960 by Intel has "mixed the cards" in the RAID game quite a bit. Non-intel CPU's got a chance and some Xscale-only startup competition has been founded, e.g. Areca (though there have been Areca models that do run on non-Xscale CPU's). The dot.com bust, the growing market acceptance of SATA (?) in servers and even the maturing open-source soft-RAID implementations in Linux/xBSD have just been additional nails in the Adaptec coffin.
The current "universal SATA/SAS" family (starting with 3800 series) is actually pretty good. The SFF-8087 with SGPIO support are the best SAS/SATA interconnect ever.
Some of our customers still demand Adaptec as "the top-notch RAID controller brand".
I tend to prefer Areca, which has similar features and IMO a richer yet lighter-weight management interface - but some customers are difficult to convert :-)
The BIOS interface to Adaptec cards has traditionally been fairly spartan (compared to e.g. Areca, but certainly on par with or better than MegaRAID, 3ware and others). Makes me wonder how many people are actually coding the firmware, BIOS and OS-based tools at Adaptec and the other vendors. I wouldn't be surprised if it's just a fairly narrow team of people, maybe down to 2-5. How much fluctuation is there in the core team, across all the ups and downs and mergers? Is anyone of the original AACRAID developers still working on the firmware? To me as a techie, the set of features and capabilities is actually the decisive selling point - rather than press announcements, acquisitions, stock splits, hostile takeovers, board-level coups and all the other corporation games...
Adaptec wanted to buy Symbios? Wow, didn't notice that :-) To me, Symbios has always been a part of LSI, a key part of the LSI SCSI expertise and excellence, up to U320.
Did you say that Adaptec bought some RAID stuff from IBM? I thought the MegaRAID acquisition path was AMI->IBM->LSI :-)