Hi everyone. I'm pretty new to SIEM and security monitoring, so please bear with me if my question is basic 😅.
My company is moving some workloads to Azure but we still have a big on-prem footprint (servers, network gear). We're looking at a proper security solution and the names that keep coming up are Microsoft Sentinel, CrowdStrike Falcon, and Splunk (I know the title says "Sentinel" but I meant Splunk, sorry!). I'm a bit lost on where to even start comparing.
Can anyone share experiences running these in a hybrid setup? I'm especially curious about the data collection part—like, how do you get logs from an old on-prem firewall into Sentinel? Is it a huge headache compared to the others? And is the cost as unpredictable as some people say?
Just looking for some real-world pros and cons to help us narrow it down. Thanks in advance for any guidance!
I'm a DevOps engineer at a mid-size e-commerce company (~300 employees). We migrated from on-prem VMware to a hybrid Azure setup last year, and I manage the logging pipeline for both environments.
1. **Pricing clarity - Splunk is the most unpredictable**
Splunk charges by data ingestion volume, which can spike 3x during incidents and surprise you. At my last shop, our bill jumped from $12k to over $30k in a heavy month. Sentinel charges per GB ingested but includes many Azure-native logs free. CrowdStrike is per-endpoint, usually $150-200/endpoint/year, which is predictable but adds up fast.
2. **On-prem log collection setup effort**
Sentinel needs a Linux VM (the "Log Analytics agent") on-prem to forward syslog or flat files. It's a manual config, about 2-3 hours per source type. CrowdStrike's Falcon agent is a single lightweight package you push to servers. Splunk Universal Forwarder is also simple, but you'll spend time tuning parsers for custom log formats.
3. **Hybrid-specific win - CrowdStrike's single pane**
If your priority is endpoint detection (EDR) across cloud and on-prem servers, CrowdStrike's console shows everything identically. Sentinel requires you to stitch together its own alerts with Defender for Endpoint (or a third-party EDR) for a full picture.
4. **Azure-native advantage - Sentinel's built-in connections**
If you're using Azure AD, Office 365, or Azure resources heavily, Sentinel ingests those logs with one-click. For a pure Azure shop, this is a no-brainer. For hybrid, you get a split view: Azure logs are trivial, on-prem logs require the extra legwork I mentioned.
Given your hybrid setup, I'd pick Sentinel if you're committed to the Microsoft ecosystem and can handle the on-prem agent setup. But tell us: what's your team's biggest priority (endpoint security vs. log correlation vs. cost predictability) and do you have any existing Microsoft 365 E5 licenses?
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That's a solid breakdown of the pricing and setup effort, especially the point about Sentinel's native Azure logs being free. That's a huge plus if you're already deep in their ecosystem.
I'd just add one caveat about > CrowdStrike's single pane. While their console is fantastic for endpoints, you still need something else for network and application logs from your on-prem gear. So the "single pane" is a bit of an illusion if you're looking for a full SIEM. It really depends if your primary goal is EDR or holistic log correlation.
Have you looked at using a third-party log shipper, like Cribl or even a basic rsyslog setup, to feed on-prem logs into Sentinel? It can sometimes simplify that manual config you mentioned.
Good question, and it's smart to ask about the hybrid part. That's the key detail. I've just been through this evaluation for my own team.
The agent for forwarding logs, the one user58 mentioned, is called the Azure Monitor Agent now, not the Log Analytics agent. It's a small but important distinction. Getting that agent on a server on-prem is pretty simple, but for a dedicated appliance like your old firewall, you're probably looking at sending its syslog to a forwarder VM first. That's the extra step that can be a headache.
Sentinel's pricing feels predictable on paper, but the potential surprise is with "non-Azure" data sources. If you lean heavily on it for your on-prem gear, your bill will reflect that directly. That's different from Splunk's surprise spikes during an incident, but it's still a variable cost based on usage.
For your situation, I'd be curious what your primary goal is. Are you looking to meet an audit requirement and collect logs, or is the focus on threat hunting across both environments? That answer might steer you toward one over the others.
You've hit on the core challenge with a hybrid setup, which is the data ingestion architecture. Getting logs from that old on-prem firewall is conceptually the same headache for all three, but the implementation differs. You'll need a forwarder.
With Sentinel, as others said, you'd stand up a Linux VM (or use an existing Windows server with the AMA) to act as a syslog collector, then forward to Log Analytics. The "huge headache" factor isn't so much the setup, but maintaining that extra infrastructure, parsing the logs correctly, and managing the ingestion costs for that non-Azure data.
For a real-world pro: if you're committed to Azure, Sentinel's tight integration means you can have conditional forwarding logic built in, so you only send the relevant security logs, not the firewall's entire traffic log. That's a direct cost control the others can't match without extra tooling. The con is you're now a part-time log pipeline admin.
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Great questions, and I'm in a similar boat trying to understand the on-prem log part. For that old firewall, my understanding is that you're always setting up a middleman server to collect its syslog, no matter which SIEM you pick. That seems like a universal headache.
But on the cost question, isn't the difference that with Sentinel, you're paying for that forwarded firewall data as "non-Azure" ingestion? So the cost is predictable per GB, but your bill grows linearly with your on-prem logging. With Splunk, a sudden spike in that same data during an attack could cost way more.
Is that the right way to think about it?
You're right about the universal headache of the forwarder, but you've also nailed the cost distinction. Predictable linear growth versus unpredictable spikes during an incident is exactly it.
Here's a new wrinkle though: the real cost trap with Sentinel isn't just the per-GB for on-prem data. It's the temptation to turn on every data connector because "it's there," and suddenly you're ingesting verbose application debug logs from on-prem that you don't need for security. With Splunk's shock bills, you notice immediately during an incident. With Sentinel, you might not notice the creep until the quarterly review.
Your firewall logs are a perfect example. You need to parse them to drop the useless noise (like routine allowed traffic) before they leave your datacenter, or you'll pay to store and analyze bytes that add zero value. A tool like Cribl or a well-tuned syslog-ng filter on your forwarder VM isn't optional, it's cost control.
Forget the comparison until you nail down your own data pipeline. Getting logs from that old firewall is the same core problem for all three. You're setting up a syslog forwarder VM on-prem regardless.
The main difference with Sentinel is you're paying per GB for that firewall data, while CrowdStrike won't even take it. Splunk will charge you more when you actually need it during an incident.
Real-world pro: Start by auditing what you actually need from that firewall for security. Most of its logs are noise. If you send everything, Sentinel's bill will be predictable but high. Splunk's will be unpredictable and potentially ruinous.
Numbers don't lie