Tuesday, December 3, 2019

Expanding your storage array

So you want to connect some drives to your server! We have plenty of options here, i hope you saved a PCIe slot!

Lets Begin, first lets go over the methods of connecting drives internally, you may already be familiar with the most common method, Sata ports.

But, often enough, we don't have enough of them, Your first answer to that might be to search for a Sata Expansion Card, which is great, you are on the right path, but really quickly you will start to see just how deep this rabbit hole goes...

Maybe eventually you made it through some solid channels and got some good advice, Perhaps someone suggested you look into LSI branded cards, or maybe some HP Expander cards, depending on your use case.

Now instead of going over the VAST list of options we have, i'll go over what i believe to be the most common scenarios...

We have two main categories to look at, 
connecting drives internally, and connecting your server via cable to a seperate storage array / disk shelf/DAS (externally) ....or maybe you need to do both.

I'm a big fan of software raid, connecting Just a Bunch Of Disks (JBOD) together....no really, JBOD is a real term used....

Ok so you want to connect....4.....8.....12....16 drives internally, Lets take a look at how we can do that.

Before we dig into the meat and PCB, lets take a look at.....Cable options!
So more often than not you are looking at using one of these mini sas to sata cables for internal connections, they allow you to connect one port to your...as of yet unmentioned LSI HBA card, to 4 physical hard drives.

They can be found HERE! and are very affordable.

So lets keep this in mind, one mini SAS connector will allow us to make 4 sata connections.

Ok, now we can dive into the controller cards, LSI and later on, HP cards to be exact.

LSI SAS 9211-4i 
LSI SAS 9211-8i 
LSI SAS 9201-16i

Pay attention to the last section of numbers and letters, a good rule of thumb is to use this number to understand how many drives each card can handle....4, 8, and 16, each with 1, 2, and 4 mini sas ports on the card, remember, one mini sas allows 4 sata drive connections. You can see the silver port on the right hand side of the cards below.


Now maybe you are wondering what that little "i" at the end stands for, and if you guessed Internal, you'd be correct!

Up until now we have been focusing on purely internal connections...now i guess it is true if you had one of these cards in Machine-A and got a long enough cable and decided to route it out the back....or front of Machine-A and into a second machine....or Machine-B and connect the 4 sata ports to drives within this second machine......you can, but i don't recommend it. A safer way to do this would be to look into some cards with an "e" designation for external.

LSI SAS 9200-8e
LSI SAS 9201-16e
LSI SAS 9202-16e

These cards are going to allow you to connect one physical machines hard drive array to another physical machine, and allow you to treat them as if they were internal drive on the machine your connecting to.

These cards would be placed in your "Compute" server, the machine you want to access the drives from, and with the use of a cable, ran to another machine that has a similar....but not the same HBA card or controller. 

Some common uses would be NetApp gear like the DS4243 or DS4246, 
If you plan to go in that route, make sure to get the correct cable - QSFP+ (SFF-8436) / Mini SAS (SFF-8088)

I recommend going the NetApp route, the used hardware can be found really cheaply on ebay, as of now, around $150-$200 and can support 24 drives.

but maybe you want to get your hands dirty and build your own disk shelf, in that case i would suggest using something like this..

HP SAS Expander
LSI SAS 9212-4i4e (4 internal sata ports...not mini sas)

Id recommend the HP SAS expander, it can be found for very cheap, and it can support up to 28 internal drives, as well as allow you to run a cable from said card, to another physical machine and access those drives, this is great for creating your own Direct Attach Storage or DAS for short.

With the two cards above, the general layout would be to install one into a machine (your disk shelf / DAS). To do that, all you really need is a motherboard to power the card and drives, a power supply, and some mini sas to sata, or sata cables if you you use the LSI card. Connect all your drives, and give them power.

On the "Compute" server end (separate physical device), you would install one of the above LSI SAS 9200-16e\8e\4e (External) port cards and run a cable between the two with an SFF-8088 cable.

Just be careful to get the HP SAS Expander with the green pcb board, the older yellow ones can not be firmware upgraded.

This was a very scaled down introduction into HBA / Raid / SAS cards/expanders, there are many options to use and many different scenarios to work through but i believe this covers the top 3, internal connections, external connections and both internal and external connections.


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