Local Storage vs SAN ...
-
We are planning a server upgrade and I find myself faced with the question of whether a SAN is necessary. I know there have been many posts both here and on other forums about SANs being oversold in situations where they are not needed. My gut instinct is that my situation is one that really doesn't require a SAN, yet I still find myself unsure that I understand the various questions that I should be considering when making this decision.
I bought a copy of Linux Administration Best Practices by @scottalanmiller and am reviewing the chapters on system storage, in particular the parts on SANs, local storage and replicated local storage.
Our needs are not sophisticated. We will have only a handful of VMs. A file server, sql server, freepbx, inventory management system server, security system server and an internal application server for a few internal tools. For most of these we can afford some downtime in the event of a host failure. The exception is really the SQL server. While it would not be catastrophic for some downtime it would be far superior from a continuity perspective if it could fail over to a secondary host if necessary.
With that in mind, I had planned for two hosts so we could survive a failure of one of them. My primary confusion though is how would I accomplish replicated local storage. Is this functionality that the hypervisor must provide? The best practices book mentions several technologies (DRBD, Gluster, CEPH) that can be used for RLS but I would think that these would have to run in the hypervisor itself and not as separate VMs on the host. Is that correct?
In general, for relatively small environments such as mine, is it feasible to even attempt local storage replication? Our MSP has quoted an EMC SAN device to the tune of $25k so that VMs could be migrated between hosts with storage being on the SAN. What would an implementation without the SAN look like if I wanted to maintain the replication and the ability for the VMs to be migrated between hosts?
-
@BraswellJay said in Local Storage vs SAN ...:
question of whether a SAN is necessary.
LOL, necessary? The question should be "under what scenario would it be acceptable?"
There's not been a mainstream acceptable use of SAN in like 18 years. It has extreme niche edge cases, it's not that the tech isn't real. But there's no normal business case where it should even be proposed, let alone seriously considered or used.
-
@BraswellJay said in Local Storage vs SAN ...:
My gut instinct is that my situation is one that really doesn't require a SAN, yet I still find myself unsure that I understand the various questions that I should be considering when making this decision
There is only one question:
Can you do this task WITHOUT a SAN? SAN is never desired only required at certain times.
-
@BraswellJay said in Local Storage vs SAN ...:
I bought a copy of Linux Administration Best Practices by @scottalanmiller and am reviewing the chapters on system storage, in particular the parts on SANs, local storage and replicated local storage.
woot woot!!
-
@BraswellJay said in Local Storage vs SAN ...:
Our needs are not sophisticated. We will have only a handful of VMs. A file server, sql server, freepbx, inventory management system server, security system server and an internal application server for a few internal tools. For most of these we can afford some downtime in the event of a host failure. The exception is really the SQL server. While it would not be catastrophic for some downtime it would be far superior from a continuity perspective if it could fail over to a secondary host if necessary.
Remember... SAN causes downtime, it cannot protect against it. If you are concerned about stability, then SAN should be ruled out even more. SAN is only okay when you are willing to take on extra risk because you want some other factor.
If stability or performance are your top priorities, then local storage wins. If you want lower performance, lower stability in exchange for massive scale consolidation then SAN can enter the picture.
-
@BraswellJay said in Local Storage vs SAN ...:
Our needs are not sophisticated. We will have only a handful of VMs.
That right there should have always taken SAN off of the table. Even twenty years ago, that wouldn't have allowed it to be viable.
-
@BraswellJay said in Local Storage vs SAN ...:
With that in mind, I had planned for two hosts so we could survive a failure of one of them. My primary confusion though is how would I accomplish replicated local storage.
How would you do it with SAN?
Do it the same with local storage. The real problem is that you don't do it with the SAN, someone pulls a shell game and gets you to look the other way and ignore the risks. With local storage, you are paying attention and actually trying to mitigate the risk (even though the risk is much less.)
Remember.. ANYTHING with SAN is more reliable without the SAN. If the SAN "feels" reliable, it's because you've missed where the risk was shifted. No exceptions. SAN adds complications and points of failure without any reliability benefits (it's simple physicals, it's impossible for a SAN to be beneficial or useful in a reliability discussion - it only makes it riskier, no exceptions possible.)
-
@BraswellJay said in Local Storage vs SAN ...:
The best practices book mentions several technologies (DRBD, Gluster, CEPH) that can be used for RLS but I would think that these would have to run in the hypervisor itself and not as separate VMs on the host. Is that correct?
They are run wherever the storage is used. The are the same technologies necessary to make a SAN reliable or local storage (remember... from the perspective of the SAN, it is all local storage - the tech doesn't change.)
DRBD, Gluster and CEPH typically run on the hypervisor. But they can also run as a VM. There are lots of ways to design reliable storage. It's even possible to make SAN reliable, but never AS reliable as not SAN.
-
@BraswellJay said in Local Storage vs SAN ...:
Our MSP has quoted an EMC SAN device to the tune of $25k so that VMs could be migrated between hosts with storage being on the SAN
And hopefully your fired them on the spot. Never let them in the door again.
-
@BraswellJay said in Local Storage vs SAN ...:
so that VMs could be migrated between hosts with storage being on the SAN.
Okay but who cares? That's not where your risk is. The risk is 99% in the SAN. Where do you migrate when the SAN fails?
-
MOST IMPORTANT THING>>>>>>>>>>>>>
You are asking the wrong questions. You need to start with "the goal" and ask questions that get you there.
In theory you are proposing that your goal is high availability, but other things you state prove that high availability shouldn't be on your radar. So you have a goal problem right from the start.
Because you have a goal problem, it is really easy to get tricked by the MSP scum that are trying to screw you over (they are seriously trying to screw you, I'm 100% serious when I say to walk them out the door and never speak to them again - these people hate you and your company and will hurt you just for fun.)
They are taking advantage of you. They also are not an MSP, you should not call them that as that, as well, is a sales trick to make them sound like consultants instead of sales people. They are not IT, they are sales. They don't represent your business needs, they represent the vendor. They don't propose what is good for you, they propose what makes EMC the most money. They are a VAR, they can't be in IT if they also do sales. The two by definition have to be exclusive (conflict of interest at the most core level.)
They are a VAR willing to do anything to make a quick buck.
-
@BraswellJay said in Local Storage vs SAN ...:
yet I still find myself unsure that I understand the various questions that I should be considering when making this decision.
This, too, tells you....
If you don't know, then SAN isn't viable. You'd know, you'd have no other choice.
For normal shops, only single servers make ANY sense. In super rare situations, where high availability matters AND you don't run high availability workloads (who falls into this bizarre niche???) then having HA here would always be from hyperconverged solutions, always.
-
I'm going to make a video just for this thread BUT, watch this video first while I'm making it...
-
@scottalanmiller said in Local Storage vs SAN ...:
I'm going to make a video just for this thread BUT, watch this video first while I'm making it...
LOL - nice!
-
Just recorded a forty minute video on this, lol. Uploading now.
-
It's taking a long time to upload
-
@scottalanmiller said in Local Storage vs SAN ...:
It's taking a long time to upload
You know, there are no issues with plugins on my nodebb systems. You should really look closer at what your errors are.
-
@JaredBusch said in Local Storage vs SAN ...:
@scottalanmiller said in Local Storage vs SAN ...:
It's taking a long time to upload
You know, there are no issues with plugins on my nodebb systems. You should really look closer at what your errors are.
I'm not uploading it HERE. I'm uploading it to YouTube.
-
@BraswellJay said in Local Storage vs SAN ...:
We are planning a server upgrade and I find myself faced with the question of whether a SAN is necessary.
No, a SAN will not be needed.
What SAN provides is shared storage. Today the preferred solution for shared storage is a vSAN. vSAN is basically local storage from several hosts networked together and replicated. It provides shared storage for the hosts. DRBD, Gluster and Ceph are simply technologies used to build a vSAN.
But maybe you don't need that either. Most don't.
The real question is: what are the business requirements and budget for the applications you run?
-
