AOC-SASLP-MV8 vs AOC-SAS2LP-MV8 speed difference

[squirrellydw]

If I have a AOC-SASLP-MV8 which only supports 3G and buy the new one AOC-SAS2LP-MV8 which supports 6g how much of a difference do you think I will notice?

[garycase]

In normal array operation, NONE.

 

With parity checks and drive rebuilds, it depends on the areal density of your drives ... but with modern 1TB/platter (or larger) drives you should notice a very nice bump in the speeds.    The difference isn't because of the SATA-II vs. SATA-III support ... but because the SAS2 is using 8 PCIe v2 lanes (4GB/s total bandwidth) vs. 4 PCIe v1 lanes (1GB/s total bandwidth).

 

 

[squirrellydw]

Thanks. And difference in pre clearing drives?? 

[garycase]

Thanks. And difference in pre clearing drives??

 

No, pre-clearing a drive wouldn't be any faster.

 

[ohlwiler]

Checkout this post by Jonnie.Black:

 

http://lime-technology.com/forum/index.php?topic=43026.msg410578#msg410578

 

Note that the X7SBE uses v1 PCIe and only the x8 slot is "fast". The x4 slot shares bandwidth with the native SATA ports over a DMI 1.0 link (see page 8 of the Supermicro X7SBE manual for the Intel 3210 chipset block diagram). Your best bet to increase parity check speed is to add a Supermicro SAT2 to the PCIX buss. Available for $8.65 via ebay.

 

http://www.ebay.com/itm/Supermicro-AOC-SAT2-MV8-8-Port-SATA-Low-Profile-Controller-Card-/252182918505?hash=item3ab745f569:g:rXMAAOSwys5WU4ZA

[garycase]

... Your best bet to increase parity check speed is to add a Supermicro SAT2 to the PCIX buss. Available for $8.65 via ebay.

 

You should indeed notice a modest difference in parity check speed if you switch to the older PCIX controller ... but it's debatable whether or not it's worth the bother.

 

It depends on just what you were looking for when you asked:

...  how much of a difference do you think I will notice?

 

As I noted earlier, in normal array operations (reads, writes, streaming media, etc.) the answer is NONE.

 

But if parity check speeds are what you're looking to improve, there are several things you could try:

 

(1)  If your SASLP is plugged in to the x4 slot, move it to the x8 slot.  As noted above, the x4 slot is sharing bandwidth with the onboard SATA ports -- the x8 does not.    So while you'd still have bandwidth constraints, you'd likely see a nice bump in parity check speeds by simply moving the card.

 

(2)  If you don't mind tossing a few $$ for the SAT2 PCIX card, buy one of those and move your drives from the SASLP to it.

Note that the gain will be pretty nominal (probably 20-30%), but it should be faster.    This is, of course, a "throwaway" card, as it's very unlikely you'll want to use it in any future system.

 

(3)  Buy the SAS2LP.    While you won't get the full benefit of this card in your PCIe v1 system, you'll still have 2GB/s of bandwidth available, so it should come close to not bottlenecking any of the attached drives.  [The theoretical bandwidth is 250MB/s per drive; but based on Johnnie's results with it in a v2 slot it's likely to have actual performance lower than that -- if it's exactly half of what Johnnie saw it would be 160MB/s ... which would slightly bottleneck high density drives on their outer cylinders => but not enough that you'd be likely to really notice it]    And of course this card would move nicely to a newer setup, and would then definitely not be a bottleneck with a PCIe v3 (or even v2) slot.

 

 

[squirrellydw]

Thanks, I think I will check to see what slot I have my SASLP in.  I will do that in a few weeks.  Thinking about upgrading my system in a few months anyhow.

 

As always, thanks for the great advice.

[JorgeB]

(3)  Buy the SAS2LP.    While you won't get the full benefit of this card in your PCIe v1 system, you'll still have 2GB/s of bandwidth available, so it should come close to not bottlenecking any of the attached drives.  [The theoretical bandwidth is 250MB/s per drive; but based on Johnnie's results with it in a v2 slot it's likely to have actual performance lower than that -- if it's exactly half of what Johnnie saw it would be 160MB/s ... which would slightly bottleneck high density drives on their outer cylinders => but not enough that you'd be likely to really notice it]    And of course this card would move nicely to a newer setup, and would then definitely not be a bottleneck with a PCIe v3 (or even v2) slot.

 

Since my test board has the option to change the PCIe generation I did some quick tests and the SAS2LP with 8 disks can do 200MB/s on an 8x gen1 slot.

 

Added those and also PCIe gen2 4x results for it and the Dell H310 to my post as it can be useful to other users.