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Don't be afraid to be SAS-sy ... a primer on basic SAS and SATA

jgreco

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#61
I got a LSI 9217 card and without even any drives plugged in, the heatsink is so hot I almost burned my finger.
Is this normal? Are the chips supposed to be this hot?
The LSI cards are typically intended to be run in a server with substantial forced airflow. If you do not have airflow past them, they typically go thermonuclear. The typical LSI chipset is dissipating something around 10 watts, so it does not really take a huge amount of airflow to cool them, but if you create a zone without airflow, they do suffer and can even do bad things.

Many, but not all, LSI cards come with vented slot covers which hopefully your card has. If you are not building inside a regular server chassis, you may need to arrange cards to create airflow. Some people advise to add a chipset fan to the LSI card, but in general I think this is a bad idea, as the fan will eventually cook, and then the LSI will cook worse, and this can potentially spew spurious write errors into your pool.

I keep intending to order some custom double-height LSI heatsinks but there's some variety in the shapes and the cost is nearly unjustifiable. Plus I generally deploy these things in real server chassis.
 

jgreco

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#62
Thank you very much, @jgreco . I've been playing with FreeNAS for a year, now, have read this page twice before, and it was lost on me. I just ordered a new Super Chassis with a TQ backplane, and this helped clarify a lot of pieces that have been floating around. Looks like I'll need an expander to round out my system, and now I know.
You are entirely welcome to tell me where I failed to make things clear. I try my hardest to place myself in a "newbie's" shoes when writing this sort of thing. That does not mean I'll be successful. But you should definitely assume it is my intent to make this clear to anyone who is in your situation, and telling me where I failed is beneficial to everyone.
 

Octopuss

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#63
The LSI cards are typically intended to be run in a server with substantial forced airflow. If you do not have airflow past them, they typically go thermonuclear. The typical LSI chipset is dissipating something around 10 watts, so it does not really take a huge amount of airflow to cool them, but if you create a zone without airflow, they do suffer and can even do bad things.

Many, but not all, LSI cards come with vented slot covers which hopefully your card has. If you are not building inside a regular server chassis, you may need to arrange cards to create airflow. Some people advise to add a chipset fan to the LSI card, but in general I think this is a bad idea, as the fan will eventually cook, and then the LSI will cook worse, and this can potentially spew spurious write errors into your pool.

I keep intending to order some custom double-height LSI heatsinks but there's some variety in the shapes and the cost is nearly unjustifiable. Plus I generally deploy these things in real server chassis.
Hm.
That's going to be interesting.
DSC_0019.JPG

There's not really any airflow at the top of the case so I'll have to observe once the server is fully up and running (don't have any disks ready for the NAS yet).
The case (Phenom M) is a little obscure when it comes to airflow. And I don't really intend to add anything to the top side (not if I can help it).

Maybe the heatsink is doing a good job though, because while I almost burned my finger touching it, the underside of the card is just somewhat warm.
 

danb35

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#64
Looks like it might be worth coming up with a way to mount a fan to that heatsink.
 

Stux

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#65
There’s a fan mount at the top of your picture. Put a fan there and have it blow at the lsi Heatsink. Probably doesn’t have to be spinning fast.
 

jgreco

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#67
Do these cards have any temperature sensors or something by chance?
Depends on the generation of the card. I think they started doing that with the SAS3 HBA's. Some of the SAS2 RAID controllers (926x/927x/928x) do, some don't. Most of the HBA's that are good for FreeNAS are what LSI considered "entry-level" cards so they didn't put fancy features on them.
 

ere109

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#68
You are entirely welcome to tell me where I failed to make things clear. I try my hardest to place myself in a "newbie's" shoes when writing this sort of thing. That does not mean I'll be successful. But you should definitely assume it is my intent to make this clear to anyone who is in your situation, and telling me where I failed is beneficial to everyone.
It isn't so much a failure on your part. These are complex concepts, and until one ever enters the arena and starts exploring to understand the different hardware options, they're not ready for this.
What helped me was the decision to move to hot swap. Suddenly i was reading about LOTS of equipment and technology. So i now knew the terms, but was unsure what they did. Reading your post filled in those blanks.
I ordered a device with a TQ backplane, and suddenly understood. My HBA has 8 sas ports, but I saw the SFF connectors on certain hardware, so then understood the difference between interfaces, and read another post about forward and backward cabling (can't recall if you address that). The only possible suggestion I might have would be a simple bullet point index at the front to break down the chronology of SAS design, and perhaps a note on expander vs second HBA (cost vs capacity). When a reader is ready for it, this is a great place to turn for answers.
 
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