Could someone please explain how this device works?

N

natermeister

Limp Gawd
Joined
Dec 26, 2005
Messages
463
mAGE316U40-PCI-E-Exp.

From the looks of it, you install a PCIe RAID controller into this box, but then what do you connect that to? Another RAID controller in the server?

Some help here would be greatly appreciated. I'm buying a NAS to buy some time, but in another year or so I'm going to have to build a proper storage server.

Thanks
 
Dude, that is SOOOO neat!

So, basically, what that thing does is blend the boundaries between internal and external storage.

In a nutshell, that case allows you to offload your PCIe 8x storage controller to the external case itself, giving you 16 drive bays in the process (usually the most you can get from a PCIe 8x storage controller).

It does that by bridging an 8x PCIe link from the main system through an external cable to the 16-bay case.

That is, that's what I could make of the link. It's actually a very decent storage option. There should only be a marginal increase in HDD latency (you have a 1.5 meter cable running a PCIe link that's supposed to be like 20cm long tops).

If I'm right, that's the first actual high-bandwidth PCIe extender I've seen. Sure, there's something similar with that external Asus GPU, but that's a short cable, and low-bandwidth (4x max, if memory serves me right).

Cheers.

Miguel
 
Yeah, it seems very cool. It even looks good. I'm going to check around online to see if I can find it for sale. Newegg doesn't seem to have it.

EDIT. Good lord, it's $3,400.

EDIT. Some sites have the 2U version for about $1,400. Need to look around some more.
 
Last edited:
natermeister said:
EDIT. Good lord, it's $3,400.

EDIT. Some sites have the 2U version for about $1,400.
Click to expand...
Holy s**t! That's insanely expensive! Granted, it's case+PSU+drive bays+ PCIe extender and high-quality 2GBps cable, but still, I always tend to find this kind of solution way too expensive for non-enterprise uses...

Blue Fox said:
SAS expanders are so much simpler and cheaper...
Click to expand...
It's all a matter of bandwidth, I believe. AFAIK SAS expanders can have lower available bandwidth, or at least lower available bandwidth per drive. This thing will allow at least 2GBps in each direction for a maximum of 16 drives. That is A LOT of bandwidth.

SAS expanders usually drive 4 or 8x300MBps (single or dual channel, and there is always some kind of "multiplexer" on the expander case) to a maximum of 24 to 32 drives, right? That's less bandwidth and more drives, you might hit a bottleneck earlier.

Of course if you want a real low-cost approach, then you might want to check something like a 4-port eSATA card with 4 1-to-5 Port Multipliers (I'm thinking Addonics) on an external enclosure. More cables, yes, but the cards can be cheap (especially the 2-port PCIe 1x ones, it's like €35 each). Just don't expect performance to be stellar (though a 10-drive WHS box is perfectly fine with 8 drives being run over the PCI bus, 5 of them over a PM, here).

Cheers.

Miguel
 
Find me a RAID card that is limited by SAS expanders and then we'll talk (they don't exist). Current SAS expanders provide more than the 2gb/s of bandwidth that you quote (2.4gb/s actually). SAS expanders are also a lot more practical when it comes to scalability. You can daisy-chain them.
 
If the sata interface bottleneck is whats killing your WHS, I want your networking gear!!!
 
Can anyone give me a rundown on SAS expanders? Where to get them, how they work, drive chassis that use them, ect
 
Think USB hub, but for SAS HBAs. That's really the simplest way of explaining them. They are difficult to find unfortunately, but you can use them with whatever chassis you would like. I'm going to put mine in a Norco 4020. The one I have comes in two form factors. You can either get a version that is the same form factor as a mITX board (link) or just as a regular expansion card (link). The expansion card form factor does not need to be inserted into a motherboard. You can also get them integrated into cases (Supermicro makes some for example). If you do decide to get one, stick to the HCL!
 
Blue Fox said:
Find me a RAID card that is limited by SAS expanders and then we'll talk (they don't exist). Current SAS expanders provide more than the 2gb/s of bandwidth that you quote (2.4gb/s actually). SAS expanders are also a lot more practical when it comes to scalability. You can daisy-chain them.
Click to expand...
I'm not saying the RAID card is limited by the expanders. I'm saying available bandwidth per drive can become lower faster with SAS expanders. Especially if you daisy-chain like 60 drives to the same card and have multiple (20+) parallel requests to the drives (and have high-throughput drives, of course).

Granted, not something very likely to happen in anything but enterprise-level applications, but it can happen. In that regard, the limited expandability of the 16-drive setup the OP asked about might be more useful.

In everything else, I'm with you.

jay2472000 said:
If the sata interface bottleneck is whats killing your WHS, I want your networking gear!!!
Click to expand...
You and me both... lol

I'd be happy with a 2-port PCIe 1x controller and two 1-to-5 port multipliers for my WHS. More bandwidth than I need :p I'll be hard-pressed to have enough simultaneous connections to hit more than 100MBps hehehe

Cheers.

Miguel
 
Blue Fox said:
Think USB hub, but for SAS HBAs. That's really the simplest way of explaining them. They are difficult to find unfortunately, but you can use them with whatever chassis you would like. I'm going to put mine in a Norco 4020. The one I have comes in two form factors. You can either get a version that is the same form factor as a mITX board (link) or just as a regular expansion card (link). The expansion card form factor does not need to be inserted into a motherboard. You can also get them integrated into cases (Supermicro makes some for example). If you do decide to get one, stick to the HCL!
Click to expand...

So you use an plug multiple HBAs into a single expander to create one large RAID volume?
 
natermeister said:
So you use an plug multiple HBAs into a single expander to create one large RAID volume?
Click to expand...
I think it's the other way around: you plug one or more SAS expanders to one HBA (depending on the HBA, you might be able to connect more than one expander, and expanders can connect to each other, much like USB hubs).

But in the end, yes, you can theoretically build one massive RAID array out of how many HDDs are possible to connect in a SAS domain (which is A LOT).

Of course, common sense should tell you that you are asking for serious problems if you have like 50 disks (I've read more than 20 should be avoided, even with RAID levels that have more than one redundancy disk, due to the added risk of multi-disk collapse, though other people say that's just fine; for me, unless redundancy is 1:1, I start to feel queasy when thinking about arrays with more than 10 disks, even with RAID6) on a single array. Better to have nested redundant arrays (like 50, 60, 55, 56, 65 or 66), just to be on the safe side, if you want to go that way.

But anyway, that's already a bit OT, I think.

Cheers.

Miguel
 
__Miguel_ said:
I'm not saying the RAID card is limited by the expanders. I'm saying available bandwidth per drive can become lower faster with SAS expanders. Especially if you daisy-chain like 60 drives to the same card and have multiple (20+) parallel requests to the drives (and have high-throughput drives, of course).

Granted, not something very likely to happen in anything but enterprise-level applications, but it can happen. In that regard, the limited expandability of the 16-drive setup the OP asked about might be more useful.

In everything else, I'm with you.


You and me both... lol
Click to expand...
Thing is, no processor on any SAS HBA can handle more throughput than SAS expanders provide at the moment, so they aren't the limiting factor.
 
Good point, actually. But I was referring to the lack of bandwidth exactly because of the HBA... :p

It seems we're on the same page, right?

Cheers.

Miguel
 
You must log in or register to reply here.
Back
Top