Graylog vs Splunk for 50-500 server SMBs: 3-year TCO and scaling pain points
Open-source vs commercial for a mid-sized estate. Concrete 3-year TCO numbers, scaling pain points, and vendor risk. The decision is not technical — it is about control.
Graylog vs Splunk for 50-500 server SMBs: 3-year TCO and scaling pain points
TL;DR
- For a 50-500 server SMB, Splunk Enterprise/Cloud reaches 80,000-300,000 EUR/year over three years, depending on log ingest volume.
- Graylog Open + ecosystem (OpenSearch, MongoDB) costs ~5,000-15,000 EUR/year in hardware/cloud + 1 part-time FTE for ops.
- The difference is not just budget — it is also vendor lock-in risk and the ability to operate the SIEM without external dependence.
- Splunk wins on UX and initial configuration speed. Graylog wins on TCO, sovereignty, no surprise renewals.
- For regulated SMBs (NIS2, financial, legal), open-source on-premise is overwhelmingly the right choice.
The Graylog vs Splunk comparison is one of the oldest in the industry. It has existed for nearly 10 years, and most public analyses are either vendor-sponsored or written for large enterprise. For 50-500 server SMBs — the actual segment of many companies in CEE — concrete analysis is missing.
This article takes the position of a CTO evaluating SIEM for an estate of approximately 200 servers. The numbers are indicative but reflect real deals and publicly visible TCOs.
Comparison setup
Typical SMB profile we are referring to:
- 200 mixed servers (Linux + Windows).
- 50 business applications / containers.
- ~5,000-15,000 events/second peak (e-commerce, mid-tier fintech).
- Daily log volume: 100-300 GB.
- Legal retention: 12 months online + 36 months offline.
- SecOps team: 1-3 people with other responsibilities.
- Regulation: GDPR + NIS2 (if critical/important entity).
This profile fits most companies we work with on AEGIS — mid-tier banks, fintechs, regional cloud operators, mid-size public institutions.
Splunk: what you get and what it costs
Splunk is the de facto standard. Excellent UX, thousands of apps in Splunkbase, advanced search capability (SPL — Search Processing Language), advanced correlation.
Licensing model. Splunk has gone through three recent models: per GB/day ingested, per workload (vCPU), and currently a hybrid. For an SMB at 200 GB/day:
- Splunk Enterprise on-prem: ~80,000-120,000 USD/year license, plus hardware (3-5 indexer servers + search head + license master).
- Splunk Cloud: ~120,000-200,000 USD/year for the same volume, no hardware but with egress traffic charges if logs come from your own cloud.
Hardware (on-prem). Official recommendation: minimum 3 indexers for HA, each 12 cores + 64 GB RAM + 4-8 TB NVMe. At enterprise hardware prices: 15,000-25,000 EUR/server. Plus search heads (2x), license master, deployment server.
Personnel. Certified Splunk admin on the market: 65-90K EUR/year. Many SMBs outsource (MSPs with Splunk expertise) at 30-60K EUR/year retainer.
3-year TCO Splunk Enterprise on-prem (200 servers, 200 GB/day):
- License: 240-360K USD (220-330K EUR).
- Hardware: 80-120K EUR (amortized).
- Personnel: 50-100K EUR.
- Total: ~350-550K EUR over 3 years.
3-year TCO Splunk Cloud:
- Subscription: 360-600K USD (330-550K EUR).
- Egress traffic: variable, 20-50K EUR.
- Personnel (less): 30-60K EUR.
- Total: ~380-660K EUR over 3 years.
Graylog: what you get and what it costs
Graylog Open is free (SSPL — Server Side Public License). Enterprise Edition (paid) adds features such as advanced audit log, archive management, premium parsers.
Licensing model.
- Graylog Open: 0 EUR.
- Graylog Operations: ~3,000-8,000 EUR/year for a mid-size cluster.
- Graylog Security: ~10,000-25,000 EUR/year if you want enterprise SIEM features.
Hardware (on-prem). Typical stack: 2-3 Graylog nodes + 3 OpenSearch nodes + 1 MongoDB node + LB. Resources: 8-16 cores per node, 32-64 GB RAM, NVMe storage scaled to log volume. On existing infrastructure: amortized ~5-15K EUR/year.
Personnel. Graylog admin is not a separate specialty — any SRE/SecOps with Linux experience learns it in 2-4 weeks. Many clients run with 0.3-0.5 FTE allocated (10-25K EUR/year imputed cost).
3-year TCO Graylog Open + ecosystem:
- License: 0 EUR.
- Hardware: 15-45K EUR (amortized over 3 years).
- Personnel: 30-75K EUR.
- Total: ~45-120K EUR over 3 years.
3-year TCO Graylog Operations:
- License: 9-24K EUR.
- Hardware: 15-45K EUR.
- Personnel: 30-75K EUR.
- Total: ~55-145K EUR over 3 years.
The difference is not just price
A 3-5x TCO difference is significant, but it is not the only argument. For regulated SMBs, non-financial considerations are equally important.
Vendor risk. Splunk was acquired by Cisco in 2024. Price or term changes at renewal are documented reality — clients that paid X in 2023 are paying 1.5-2X in 2026. With open-source there is no renewal — there are upgrades or migrations, under your own control.
Sovereignty. Splunk Cloud means logs are at the vendor. For an NIS2 or GDPR client with sensitive data, that re-opens the Schrems II problem and international transfers. Splunk Enterprise on-prem solves that, but adds operational complexity.
Internal capability. With Splunk, the SMB becomes dependent on the Splunk ecosystem — apps, integrations, specific skills. Migrating away from Splunk is a 6-12 month project. With Graylog Open, data and configuration are portable (OpenSearch + MongoDB are standard formats).
Cost predictability. Splunk has a track record of 20-40% renewal increases. Graylog Open is fixed at 0. Hardware grows predictably with log volume.
Where Splunk wins
Honesty requires acknowledging where Splunk is clearly superior:
UX and time-to-value. Splunk is configured in 2-4 weeks for an SMB. Graylog requires 6-12 weeks of tuning, custom parsers, dashboards. If you do not have internal capability and do not want to outsource — Splunk is faster.
Apps ecosystem. Splunkbase has 2,000+ apps with out-of-the-box integrations. Graylog Marketplace is smaller. For exotic integrations (specific ERPs, niche SaaS), Splunk is more likely to have something pre-built.
Complex search. SPL is more powerful than Graylog Search. For analysts doing advanced threat hunting, Splunk is the preferred tool. Graylog handles 90% of cases, but the last 10% requires extensions.
Enterprise support. Splunk has aggressive SLAs, response time in hours. Graylog Operations has support but less polished.
Where Graylog wins
Cost. 3-5x TCO difference over 3 years.
Sovereignty. Open-source on-prem, full control over data and configuration.
No surprises. No renewal, no license audit, no price increase.
Modest hardware. Graylog runs decently on mid-tier servers. Splunk indexer needs fast NVMe and lots of RAM.
Customization. Graylog plugins written in Java or Python. Suricata, Wazuh, Falco — all send logs to Graylog with minimal effort.
Recommendation per profile
SMB with 50-200 servers, no strict regulation, small internal capability: Graylog Open. Low TCO, manageable complexity. Outsource the initial setup if you do not have time (CAI Technology delivers in 4-6 weeks under a AEGIS contract).
SMB with 200-500 servers, NIS2/GDPR critical, mid internal capability: Graylog Open or Operations. Splunk Cloud does not pass a Schrems II audit. Splunk Enterprise on-prem is overkill for the profile.
SMB with 500+ servers, mature threat hunting, no compliance constraints: Splunk Enterprise reasonable if the SecOps team is mature and uses advanced SPL. Otherwise Graylog is sufficient.
Public sector, law firm, mid-tier bank: Graylog Open + local LLM for AI triage. See AEGIS for the complete stack and On-premise SIEM with a local LLM for architectural details.
Scaling pitfalls
Regardless of tool, certain problems appear at scale:
Log volume grows 30-50% per year. New applications log more, microservices multiply sources, new agents (Wazuh, Falco) add channels. Conservative budgeting = underestimation.
Retention becomes expensive. 12 months online + 36 months offline requires architecture. Splunk has SmartStore (S3 backend). Graylog uses OpenSearch ISM + S3-compatible. Plan from day 1.
Search performance. At 500 GB/day with 12-month retention = 180 TB. Ad-hoc searches on this window require many indexers, lots of RAM. Constant tuning.
False positives. More sources = more alerts. Without tuning, the operator loses confidence. Monthly tuning plan is mandatory.
Related articles
- SaaS SIEM vs on-premise TCO: 200 servers and 10k events/sec, 3-year numbers
- On-premise SIEM with a local LLM: AI incident analysis without breaking confidentiality
- AI incident analysis with a local LLM: triage from 30 minutes to 30 seconds
- NIS2 implementation — operational checklist for essential and important entities
- Pillar AEGIS — on-premise SIEM with local AI
Next steps
The Graylog vs Splunk decision does not get made in 30 minutes. It requires evaluation of internal capability, regulatory profile, 3-year plan. For a 4-8 hour workshop with your technical team, see the AEGIS page or write to contact.
Related: On-premise SIEM with a local LLM · Wazuh Active Response patterns · Why not Auth0 — Schrems II.