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Building a DAS Box

E

ericdude101

n00b
Joined
Oct 29, 2015
Messages
4
Hello Everyone,

I'm a little unfamiliar with this and was hoping to get some clarification on this subject. I am looking to build a DAS box that can host at least 12 drives, preferably 24. This DAS must also be able to connect to at least 3 host machines that will need direct access to the data. Ive seen and worked with this type of equipment at work, but cant seem to find a HBA that would support more than 8 internal drives with 4 external ports. Would it be possible to have two separate HBA's in the same DAS server that would essentially work together?
 
ericdude101 said:
Hello Everyone,

I'm a little unfamiliar with this and was hoping to get some clarification on this subject. I am looking to build a DAS box that can host at least 12 drives, preferably 24. This DAS must also be able to connect to at least 3 host machines that will need direct access to the data. Ive seen and worked with this type of equipment at work, but cant seem to find a HBA that would support more than 8 internal drives with 4 external ports. Would it be possible to have two separate HBA's in the same DAS server that would essentially work together?
Click to expand...

you need a SAS expander. Look at HP and Intel.

HP has a 36 port SAS expander but you almost always have to flash it with an updated BIOS

http://hardforum.com/showthread.php?t=1484614

Intel has a 24 port SAS expander and you can find used around 150 and if your lucky sub 150 on ebay. You cna get new from 200-250.

http://www.newegg.com/Product/Product.aspx?Item=9SIA24G28M7361
 
I'm familiar with SAS expanders, but the typical HP 36 port SAS expander only gives my one external port to use for connecting the DAS to my host servers. I have 3 hosts that need access to the data pool. How would this be done?

Some of HP's controllers like the P822 give me 4 external ports but only allow me to connect 8 drives to the card internally.
 
You cannot connect multiple hosts like that, nor can you connect any hosts to an HBA via the external (or internal) SAS ports. Hosts will need to be connected via ethernet, FC, IB, etc. You're essentially wanting NAS instead of DAS.
 
In our previous environment we had an HP JBOD with redundant controllers, it was a manages DAS. Each controller had 4 external SFF-8088 ports which were used to connect to servers that could then access the data. I want to accomplish this same setup with a homemade system.
 
Not possible outside of commercial ASIC implementations. The disks were not being directly presented to the servers anyway presumably. You're still looking at the solutions I mentioned.
 
No, the controllers in the JBOD were managing the RAID and the Disks then presenting the data to the connected hosts. Maybe those ports on the JBOD controllers were part of a SAS switch built directly into the controllers so to speak?
 
If RAID was involved, then they weren't presenting them directly like I mentioned. There wouldn't have been a need for a SAS switch. Anyway, like I said, all custom ASIC that isn't reproducible in a home environment.
 
other problem is you are going to require a SAN file system of some sort like GFS or xSAN etc... if you mount an NTFS drive twice on two different initiators terrible things happen..

I did it via FC once to see how bad it would be/how quickly it would blow up... pretty bad, pretty quick!
 
I'm betting what you have at work is something like the HP MSA P2000 G3 SAN.

http://www8.hp.com/us/en/products/disk-storage/product-detail.html?oid=4118559

With dual SAS controllers, you can connect to four servers directly via SAS with a pass-through HBA in each host while the onboard controllers in the SAN itself control the RAID array(s). My main question is, what is your need for a SAN in the first place? If all you are using is one then you're creating an inverted pyramid of doom.
 
Given the small amount of servers that need access to the data, I would suggest you look at point to point fibre channel. Your storage box would then work as a fibre channel target. You'd then be using a basic SAN rather then DAS or NAS.

Have a look on ebay for qle2464 (quad port for target) and qle2460 (single port for initiator). LC/LC fibre cables are cheap. if your cables are long, go for OM3, for short cables it doesn't matter. This will give you 4 GBit interface to the disks which should be good for +/- 300 MB/sec sequential. Bonus: You can boot from the SAN.

On the target, you can run a Linux based OS, with the LIO target presenting the block devices directly. Alternatively, you run ZoL and export ZVOL devices.

If you want to involve ZoL, there are some settings you need to make. I can help you with those if needed.

LIO target info here:
http://linux-iscsi.org/wiki/LIO
 
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