.

Edited November 16, 20187 yr by vekselstrom

Using hard drives, there won't be any difference.  Using SSD's the SAS2LP should be faster.  The only other thing is that in Canada, the SAS2 is actually about $30 cheaper.

I am new to unraid and reading forum to build my server.

 

Why no difference with sata3 (6BG/s) Hard Drives? SASLP is "only" 3GB/s, SAS2LP is 6GB/s.

So, why take benefits only SSD?

 

Probably no practical difference.  The SASLP is an x4 card, and the SAS2LP is an x8 card.  The bandwidth each is capable of depends both on the card and the PCIex revision of the motherboard.  My SAS2LP reports 2.5GB/s on a very old PCIex 1.x motherboard.  Given that modern hard drives are capable of perhaps 150MB/s even half of 2.5GB/s would have been sufficient for 8 spinners.  And both cards would have more bandwidth available on a newer motherboard... so probably no practical difference for most users.

 

SSDs change the equation, though.  They are capable of over 500MB/s and could saturate the older x4 SASLP if you hooked up a bunch of them.

 

{edit-fixed some bps vs B/s errors}

Given that modern hard drives are capable of perhaps 150Mbps

 

The modern larger 7200 RPM hard drives are now capable of 190MB/s to almost 220MB/s on the outer tracks.

As the drives get larger and the caches get larger, we need to consider these speeds.

 

From my benchmarks the larger 5900 RPM drives can get about 160MB/s on the out tracks.

Thanks.  Does that change the math, though?  I believe an SASLP should be capable of 2GB/s on a PCIe 2.0 motherboard, which looks like it would still accommodate 8 of today's fastest hard drives.

 

Mind you - given the choice I bought the SAS2LP (mostly because I wanted an x8 card for my PCIe 1.x motherboard).  The SAS2LP is essentially the same price in the US as the SASLP and more future proof.