Re: Low cost PCI-E unRAID - Supermicro AOC-SASLP-MV8 Driver/LBA questions for HW owners/users

[Andre Tomt <andre@tomt.net>]

On 01/23/2011 12:40 AM, Spelic wrote:
> On 01/22/2011 09:36 PM, Michael Evans wrote:
>>
>> Also, you are half right about this being a 'dream' system. For years
>> I've been using a carefully selected 6 port motherboard, and 3 PCI-e
>> 1x cards to get a total of 12 ports.
>
> So you are trying to reach 12 ports?
> C'mon don't be cheap, there are lightning-fast 16-ports HBA controllers
> from LSI, at 6.0gbit/sec, $350 or so. $25 per port is not much; it is
> much less than the cost of the disk you are attaching to it.
> This frees you from the choice of the mainboard, and this is important,
> firstly because you can save $$$ in there, and secondly because if the
> mainboard fails, what are you going to do? you are going to buy another
> one with 6 ports? Difficult to find... and expensive also.
> Also using 2 different controllers for your disks (part from mainboard,
> part from addon card) is a bit of pain in the *** for administration
> things, also performances would be the slowest of the two for every
> request.

Since we're talking about "non hardware raid" usage, I don't really 
understand how it would be harder to manage mixed controllers? Care to 
explain? I can't quite get the performance statement to compute, 
either.. Its not like the same I/O goes out to all controllers. If your 
other controller is slower, just put fewer drives on it. Balance it out.

Anyways, If you settle for SATA and a desktop motherboard, most mid to 
high end s1156/1155 motherboards nowadays are fitted with 6 to 8 SATA 
ports. They're in now way hard to come by - even 8 ports seems to be 
available at $130 (I spent 10 seconds looking on newegg). But then again 
not all of them will *boot* off 3TB drives - at least many of the 1156 ones.

As for on board performance, integrated Intel ICH's AHCI controllers 
tend to top out at around 750MB/s aggregate. 6 ports are usually on the 
Intel, the rest on some AHCI compatible chip from Marvell. In general 
you can expect around 1GB/s aggregated from the on board controllers at 
the same time on a standard socket 1156/1155 desktop class intel chipset 
based motherboard.

Regarding the AOC-SASLP-MV8, yes, they're not worth it - the mvsas 
driver is still buggy when used with SATA. I have heaps of issues with 
mine - at least when using Seagate 7200.11 1.5TB drives on 2.6.36.3. 
Keeps stalling and throwing IO errors (no corruption yet, though). The 
card also tops out at ~700MB/s aggregate - and we can't have any of that 
can we ;-)

So yeah, the LSI based cards are seems like a good bet if you go the SAS 
HBA route. Even the previous 3Gb/s generation can do a cool 
1600-1700MB/s if you give them 8 pcie lanes. If he ever plan to expand 
into expander (he he) territory, that bandwidth is good to have. Well, 
in a "dream system" anyway, any normal workloads are generally more 
random and much, much lower in throughput. But hey, we're going for 
bragging rights here, right? :-)