Can you saturate a 3GB Multi-Lane SATA interface

[dwchan69]

I have an adaptec 8 Lanes 3Gb SATA/SAS controller. It has 2 internal ports with 4 lanes on each port. Is that mean each lanes can burst at 3Gb with a maximum burst through put at 8 * 3Gb, or it is 3Gb per port?

 

[cyberjock]

It's 3Gb/sec per lane. Keep in mind there may be other bandwidth limitations. For example, if that card is PCI, you're going to be limited to 133MB/sec for the PCI bus. That's a whopping 1Gb/sec or so. So your controller might be wicked fast, but other bottlenecks may be a serious problem. So as the admin for your server, as you design and build it, it's important to know all of the different speeds and potential bottlenecks. Otherwise you'll get it build and then kick yourself when it performs like a dog.

 

[dwchan69]

The Card is Adaptec RAID 5805 with a PCIe interface. It is PCEe 8X and installed on the mother board 8X slot in any case. I know it is a hardware RAID card, but would FreeNAS work with a RAID controller in pass through mode?

 

[cyberjock]

Maybe. Maybe not. And even if it works, that doesn't mean it works appropriately for ZFS. Most people that choose to do passthrough when its not appropriate for ZFS find out when they lost their pool. So it's safest to just abandon the idea of RAID controllers and do an HBA and feel better about it.

 

[dwchan69]

That is fair, thus I can just connect the internal drive bay directly to the mother board. Just a fruit for though, can FreeNAS handle the RAID5 from my Adapatec as a single zdev device?

 

[cyberjock]

That is fair, thus I can just connect the internal drive bay directly to the mother board. Just a fruit for though, can FreeNAS handle the RAID5 from my Adapatec as a single zdev device?

If you start using hardware RAID and it doesn't work, you can't just plug the drives to your motherboard without losing their data. You probably know this, but I don't assume anything when answering questions because too much data has been lost as a result of knowledge gaps.

Can FreeNAS handle hardware RAID as a single vdev? Yes. It's extremely dangerous, but you can. You lose some of ZFS' best features and you introduce some serious risk of ZFS inconsistency resulting in a failed pool. You probably aren't even aware of all the reasons it's bad.

So like I said before... "it's safest to just abandon the idea of RAID controllers and do an HBA and feel better about it." If you choose to go with RAID and have problem later many of us experienced people will tell you the 10 places where we tell people not to do RAID because of experience and tell you that you've lost your data because you didn't listen to those 10 places. This happens often unfortunately. :(

 

[dwchan69]

LOL fair enough, just try to leverage HW I already have. I should be able to leverage that CARD somewhere else. As I have both internal and JBOD option. Would it be wise to have the following setup

1. Internal - ## of 3-1/2 7.2K SATA disk using onboard SATA controller
2. External - JBOD using the LSI 9207-8e with 16+ SAS 15k and SSD (if require)