Microsoft Sentinel vs Graylog: which to choose

Microsoft Sentinel alternative or Graylog: which fits your SIEM

Sentinel fits teams already committed to Azure that want a cloud SIEM billed through Azure and run in the Microsoft Defender portal, which is where Sentinel will be available only after March 31, 2027. Graylog fits teams that want self-hosted log management in their own infrastructure, with Graylog Open at no ingestion cap and paid Graylog Security or Enterprise features added only where a specific SIEM or support requirement justifies them. The choice turns on five things: daily ingest volume, how long logs must be kept, where the data is allowed to reside, whether your staff can operate MongoDB, Graylog servers and a search backend, and which SIEM features you truly need on day one.

Start with the volume and retention numbers, because they drive most of the cost on both sides. Sentinel bills per GB ingested and charges separately for retention beyond the default period, so a rising daily volume shows up directly on the invoice. Graylog Open costs no license fee, but your storage, compute and staff time scale with daily ingest times retention. Graylog's own sizing guidance advises planning storage as daily ingest times retention days times 120 percent, which gives you a starting point for a sizing exercise. Confirm with Microsoft your current tier and any commitment discount, and confirm with Graylog which edition covers the features your team plans to use.

Graylog Security and Graylog Enterprise carry annual fees, starting at 15,000 and 18,000 US dollars per year respectively according to the Graylog pricing page, each with a minimum of 10 GB per day or 100 Graylog Compute Units, and licensed on processed data with no per-user fees. If your daily volume sits below that minimum, ask Graylog how the minimum applies before assuming the paid edition is cheaper or more expensive. Also check whether you need Defender XDR correlation or Sentinel analytics rules, since those do not carry over one to one. Check the Graylog pricing page against your written scope before you decide.

When a Microsoft Sentinel alternative fits better than Graylog

This table maps common buyer situations to the platform that fits better and the condition under which that advantage holds. Read each row against your own estate, volume and team skills rather than treating any single row as a verdict. The main takeaway is that Sentinel suits Azure-centric estates with Microsoft data sources, while Graylog suits teams that can run search infrastructure and want to avoid per-GB analytics billing.

Buyer scenario	Better fit	Why and the condition it depends on
Azure-centric estate with many Microsoft data sources	Microsoft Sentinel	Built-in connectors for Entra ID, Microsoft 365 and Defender data save integration work. This holds only while most sources are Microsoft-native and the team already runs Azure operations.
Data residency or air-gapped rules that rule out a cloud SIEM	Graylog	Graylog server nodes, MongoDB and Data Nodes can run inside your own data center or isolated network. Sentinel runs in Azure, so confirm with your compliance owner whether cloud hosting is permitted for log content.
High daily volume with long retention	Graylog	Storage is sized from your own hardware and retention settings, so cost follows disks rather than ingestion charges. This holds only if your team can size indices and budget for storage growth and staff time.
Team with strong Linux and search operations skills	Graylog	Operating Graylog, MongoDB and OpenSearch or Data Node in-house is feasible for teams that already manage clusters. Without that skill, the operating effort can outweigh the licensing savings.
Team that needs prebuilt SIEM content quickly	Microsoft Sentinel	Sentinel ships analytics rules, workbooks and solutions from the portal. Graylog reaches comparable content through Graylog Security, a paid tier, so confirm which prebuilt detections your use case needs before choosing.
Existing Elastic or OpenSearch team	Graylog	Graylog uses OpenSearch as its storage backend, so staff familiar with index management, snapshots and cluster tuning transfer skills directly. This holds if the team also accepts Graylog's index model and version compatibility rules.

How Graylog gets logs in, compared with Sentinel connectors

Sentinel gets most of its inputs from managed data connectors that Microsoft maintains. Graylog gets them from inputs, collectors and pipelines that your team configures and operates, so the work moves from enabling a connector to owning the path each log takes.

Syslog and GELF inputs

Syslog and GELF inputs are the closest match to Sentinel's Syslog and CEF connectors, which rely on a forwarder in front of the SIEM. Graylog listens on the ports you open, so network devices, Linux hosts and firewalls can send directly without an agent. Confirm the listener capacity and transport (UDP or TCP) your devices use, because lossy UDP under bursts is the most common source of gaps. Test with a sample feed from each device class before you rely on it for detections.

Beats inputs for agent data

Beats inputs receive events from Elastic Beats-style shippers such as Filebeat and Winlogbeat. They take the place of Sentinel's Windows Security Events and Azure Monitor Agent collection paths when you want to keep the agent and the transport separate from the SIEM. This works well for file-based logs and Windows event logs on hosts that already run a shipper. Confirm that each Beat version you deploy is supported by your Graylog release before rolling it out widely, and check how field names map to the event schema your detections expect.

Graylog Sidecar for collector management

Graylog Sidecar is the component that manages collectors such as Beats or log shippers on hosts, pushing configuration from the Graylog server. It replaces the per-host configuration work that Sentinel's agent deployment hides behind Azure policies. It is useful when you run a fleet of Linux and Windows servers and need central control of collector settings. Plan for the work of building and testing each collector configuration, and for keeping Sidecar and collector versions aligned across the fleet.

Streams and processing pipelines

Streams and processing pipelines decide where each message goes after it arrives, which index set stores it, and which fields are parsed or dropped. In Sentinel, similar routing is split between table choice, transformations and data collection rules. Pipelines work well when you can describe parsing rules for each source, and they become a maintenance cost when many sources change format. Confirm how your pipeline rules will be tested and versioned before you connect production sources, because a broken rule can misroute or drop events silently.

Cloud and API-based inputs

Microsoft and other cloud sources, such as Microsoft 365 audit logs, Entra ID sign-ins and Azure activity, do not arrive as syslog. Sentinel ships ready-made connectors for them, while Graylog depends on the vendor's export path, a relay or a custom input you build. This is the area most likely to need ongoing engineering. Confirm with the vendor and your own environment which of these sources can be exported to Graylog, and which will need a custom input or a collector you must build and maintain. Then test sample throughput with real volumes before committing.

Capabilities side by side: Sentinel analytics and Graylog Security

This table compares how Microsoft Sentinel and Graylog handle deployment, ingestion, search, alerting, correlation, risk scoring, threat content, investigations, compliance packs and sign-in. Graylog rows name the edition that provides each feature, while Sentinel rows point you to the questions to confirm in Microsoft's current documentation. Use it to shortlist the features your team depends on before you price either option.

Capability	Microsoft Sentinel	Graylog
Deployment model	Cloud service in Azure, managed by Microsoft; cannot be installed in an isolated network	Self-managed on your own servers, cloud accounts or Docker Compose; Graylog Open is free to self-manage
Log ingestion	Microsoft data connectors and Azure Monitor sources; confirm which connectors cover your sources	Inputs such as syslog, GELF and Beats, routed through streams and processing pipelines
Search and dashboards	KQL-based hunting and workbooks in the Azure or Defender portal	Search and dashboards included in Graylog Open
Alerting	Analytics rules in the Defender portal or Azure portal	Event definitions for real-time and historical monitoring; notifications to PagerDuty, Slack and email per the Graylog Open product page
Correlation	Analytics rules; Fusion is replaced by Defender XDR correlation after the move to the Defender portal	Correlation engine included in Graylog Enterprise and above
Risk scoring and anomaly detection	Confirm current capabilities in Microsoft's Defender XDR and Sentinel documentation	Included in Graylog Security
Prebuilt threat content and investigations	Analytics templates and content hub; confirm content available in your tenant	Prebuilt threat detection content and investigations included in Graylog Security
Compliance packs	Confirm available compliance content in Microsoft's documentation for your framework	Compliance packs included in Graylog Security
Support	Microsoft support under your Azure or Microsoft agreement	Community support in Graylog Open; 24/7 support in Graylog Enterprise; confirm Graylog Security support terms in writing

Where Graylog Security's SIEM features cover Sentinel's detection work

Detection is where the two platforms differ most in packaging. Graylog Open gives you event definitions for both real-time and historical monitoring, and its product page says notifications can be sent to PagerDuty, Slack and email. That covers alerting and paging for a self-managed team. What it does not cover, on the Open tier, are the layers a Sentinel team may use daily: the correlation engine that Graylog Enterprise adds, and the SIEM features that come with Graylog Security, namely risk scoring, anomaly detection, investigations, compliance packs and prebuilt threat detection content. Confirm with Graylog which of these are included in the edition and license you are quoted, since the pricing page ties each tier to a minimum volume and a per-year fee.

A team moving existing Sentinel analytics rules should plan to rebuild them, not port them. Each KQL scheduled rule becomes a Graylog event definition or a piece of content, with its query, threshold, aggregation window, entity mapping and notification target written again against Graylog's stream and field names. Sentinel's Fusion rule and Defender XDR correlation have no one-to-one equivalent in Graylog, so any multi-stage detection you depend on needs a named replacement and a test. Export your Sentinel analytics rule inventory first, group it by data source and severity, and mark which rules rely on Microsoft-provided content. Then check each group against Graylog Security's prebuilt content and anomaly detection before estimating rebuild effort.

Coverage depth should be verified against your own inventory, not against a feature list. For each rule, run the replacement against replayed or parallel-run events and record whether it fires on the same known-bad samples, how many false positives it produces and who receives the notification. Ask Graylog and your implementation partner to show the correlation and anomaly features working on your data, and confirm which parts depend on OpenSearch versions that your Graylog release supports. Rules that cannot be matched should be listed as accepted gaps with a named owner, so that the compliance and SOC teams know what was intentionally dropped.

What Graylog's licensing and paid tiers mean for your budget

Graylog Open is free to self-manage under the Server Side Public License, and the Graylog pricing page describes it as having no volume limits and community support. The license is the first thing to read. The SSPL-1.0 is not approved by the Open Source Initiative, and it replaced the GPL v3 that earlier Graylog releases used, starting with Graylog 4.0 in 2020. If your procurement policy requires OSI-approved licenses, this matters even though the software costs nothing.

No license fee: You pay nothing to Graylog for the software itself, but you carry the infrastructure, storage, and staff time to run it.
No ingestion caps: Volume is limited by your hardware and storage, not by a license meter.
Community support: Help comes from community channels, not a contracted support obligation.
License scope: Confirm with Graylog and your legal team how SSPL-1.0 applies to your planned use, including any hosting-as-a-service use.
Features: Confirm which SIEM features you need, since correlation and threat detection content are part of the paid editions.

Before you rely on Open, confirm current terms on the Graylog Open product page and with Graylog directly.

Data location, hosting and compliance implications

Sentinel and Graylog differ most in where data sits, who holds administrative keys and which policies govern retention and access. The cards below cover the decisions that a CISO, compliance lead or platform team should settle before any cutover, and the evidence they must produce themselves. DeployOpen prepares controls and evidence for assessments, but independent auditors and certification bodies issue any audit reports or certifications.

Storage location and residency

Sentinel stores data in the Azure region of the Log Analytics workspace, so residency is set by Azure configuration and by where the workspace was created. Graylog stores logs wherever the team deploys its Graylog nodes and Data Nodes, whether in its own data center, a private cloud or a public cloud account the organization controls. Confirm which jurisdictions your sources, backups and replicas must stay within, and map each log source to a named location before choosing a design.

Key custody and administrative access

With Sentinel, the cloud provider operates the service and access runs through Azure role assignments, so the customer controls tenant administrators but not the underlying platform. With Graylog, the team controls the operating system, MongoDB, the OpenSearch or Data Node cluster and the Graylog admin accounts. Document who holds root, database and backup credentials, who can read raw events and how privileged access is logged and reviewed.

Defender portal retention and privacy rules

After March 31, 2027, Sentinel is available only in the Microsoft Defender portal. Once a workspace runs there, Microsoft Defender XDR data privacy and retention policies apply in place of Sentinel's own, and the Fusion analytics rule is replaced by Defender XDR correlation. If Sentinel is still your primary store, review these policies against your retention commitments and ask Microsoft to confirm how they apply to each data type you hold.

Identity and sign-in options

Sentinel users sign in through Microsoft Entra ID and inherit conditional access and role-based access control from the tenant. Graylog provides its own user authentication, and the Graylog user authentication documentation describes the supported options for logins and roles. Confirm whether your identity provider can be integrated with Graylog for single sign-on and multi-factor authentication, and assign roles so that analysts, administrators and auditors each see only what they need.

Air-gapped and disconnected operation

Sentinel runs only in Azure and cannot be installed in an isolated network. Graylog can be installed from Debian or RPM packages or with Docker Compose, which lets a team run it on networks without internet access, provided it stages packages, container images and threat content internally. Note that Graylog Security features such as prebuilt threat detection content depend on the product tier, so confirm the offline update path for any content your detections rely on.

Compliance evidence the team must produce

Moving to Graylog shifts evidence collection to the organization. Expect to produce architecture diagrams, access reviews, backup and restore test results, patch records, retention configuration exports and change logs for every Graylog node, MongoDB member and Data Node. DeployOpen can prepare these controls and evidence in your environment, but it does not issue audit reports or certifications, and your assessor or certification body must agree the scope and reach its own conclusions.

How retention and storage shape the cost of Graylog compared with Sentinel

The largest difference in cost comes from how each platform bills for data kept over time. Microsoft Sentinel bills analytics ingestion per GB, can reduce that rate with commitment tiers sized to your daily volume, and charges separately for retention beyond the default period. Confirm the current Azure rates for your region and for any data lake tier before you build a model, because these rates change and vary by region. Your main cost drivers are the daily volume you send, which data connectors you enable, how long you keep each table, and whether you query older data in place. Each of these multiplies directly into the bill, so a small retention change can outweigh a change in the commitment tier.

Graylog Open has no software fee, while Graylog Enterprise and Graylog Security are annual subscriptions that the Graylog pricing page lists from 15,000 and 18,000 US dollars per year, each with a minimum of 10 GB per day or 100 Graylog Compute Units. Your recurring infrastructure costs are the Graylog server nodes, the MongoDB replica set, the Data Nodes or OpenSearch cluster, storage, a load balancer, backup, and staff time for patching and upgrades. Storage is the largest of these. The Graylog system architecture guidance sizes log storage as daily ingest multiplied by retention days multiplied by 120 percent, and recommends a message journal of 3 to 5 times daily ingest on SSDs. For illustration only, 50 GB per day kept for 90 days needs about 5,400 GB of log storage and a 150 to 250 GB journal.

When you request a quote, ask the implementation partner to state node counts for each tier, the storage size per index set, the Data Node sizing, and the backup target and retention. Ask whether Enterprise features such as data tiering and the correlation engine are in scope, and whether Graylog Security is needed for the SIEM detections you plan to use. Confirm the OpenSearch version, since Graylog Security needs OpenSearch 2.0 or later and use of OpenSearch 1.x is deprecated. Finally, ask for the staff effort to run upgrades and the on-call coverage that will be provided. A written scope with these items lets you compare the Azure bill with your own infrastructure and staffing costs on the same daily volume.

Moving from Microsoft Sentinel to Graylog in phases

This sequence moves detections and log sources from Sentinel to a self-hosted Graylog cluster in controlled waves, so each source is verified on Graylog before Sentinel stops receiving it.

Inventory connectors, tables and analytics rules
The security engineering lead and the Sentinel administrator list every data connector, the Log Analytics tables each one fills, and every analytics rule, hunting query and workbook that reads them. Record the owner, the log source type and the response each alert triggers. Mark which rules are vendor-provided and which were written in-house, since in-house rules need rewriting. The step is done when each source has a row mapping it to its detections and a named owner who signs off on the list.
Size Graylog for ingest and retention
The platform team measures average and peak daily ingest per source from Sentinel billing and table reports, then multiplies daily ingest by the retention days you need and applies the 120 percent sizing factor in Graylog's system architecture guidance. Add headroom for the message journal, which Graylog recommends at 3 to 5 times daily ingest on SSDs. Confirm with your compliance lead how long logs must stay searchable, since that number drives storage more than anything else. The step is done when you have a written storage and journal estimate approved by the platform owner.
Stand up MongoDB, Data Nodes and Graylog servers
The infrastructure team deploys MongoDB as a replica set for configuration and metadata, a separate Data Node cluster for log storage, and at least three Graylog server nodes behind a load balancer, following the multi-node guidance in the Graylog documentation. Follower nodes are set so they cannot act as leader. Confirm the chosen MongoDB and Graylog versions against the compatibility matrix before installing, and plan for OpenSearch 1.x being deprecated. The step is done when cluster health checks pass and a test message sent to an input is searchable.
Build inputs, Sidecar configurations and streams
Engineers create syslog, GELF and Beats inputs, deploy Graylog Sidecar to hosts that need managed collectors, and build the streams and processing pipelines that route each source to the right index set and retention. Access groups are set so analysts see only the streams their role allows, using the authentication options in Graylog's documentation. Each source is tested against the parsing rules that its Sentinel connector used. The step is done when every planned source produces parsed, routed events in the expected stream.
Rebuild detections as event definitions and Graylog Security content
The detection engineer translates each KQL analytics rule into a Graylog event definition, covering real-time or historical monitoring, and where the license includes it, maps prebuilt threat detection content and anomaly detection from Graylog Security. Notification routes to PagerDuty, Slack or email are rebuilt to match the Sentinel incident paths. Rules that depended on Sentinel features such as Fusion or Defender XDR correlation need an explicit replacement design, and gaps are logged for review. The step is done when each inventoried rule has a Graylog equivalent or a documented decision to drop it, and test alerts reach the right responders.
Run both platforms in parallel
For a defined overlap period agreed with the SOC, sources are sent to both Sentinel and Graylog, and the SOC compares alert volume, false positives and search results for the same events. Discrepancies are traced to parsing, field mapping or rule logic and fixed before continuing. Graylog capacity is watched against the sizing from earlier, since dual running adds load. The step is done when the SOC lead accepts the Graylog alert output in writing for the sources in scope.
Cut over sources in waves
Sources move in groups, usually starting with lower-risk log types, and the Sentinel connector for each group is disabled only after its Graylog detections have been verified. Each wave has a rollback step that re-enables the Sentinel connector if parsing or alerting breaks. Ownership of on-call runbooks moves to the Graylog alert paths at the same time. The step is done when every in-scope source reports to Graylog and the wave log shows no open defects.
Export history and decommission Sentinel
Historical data is moved in a separate export workstream covered by a dedicated export guide, since exporting from Sentinel is its own project. Once Graylog holds the retention window investigations need, the team stops ingestion to Sentinel and keeps read-only access until the agreed retention period has passed. Microsoft says moving Sentinel to the Defender portal has no extra cost, but this decision concerns the platform, not the move. Confirm the exact retention and legal hold requirements with your compliance and legal teams before deleting any workspace. The step is done when the Sentinel workspace is retired under the approved retention decision and the closure is recorded.

Questions buyers ask before choosing Graylog over Sentinel

Can our team run Graylog without outside help?

Yes, if you have Linux administrators who can operate a distributed search backend, but the work is more than installing packages. Graylog runs as server nodes with MongoDB for configuration and metadata and a Graylog Data Node or self-managed OpenSearch for log storage. The multi-node guide recommends three Graylog and MongoDB nodes, three Data Nodes on their own cluster, and a load balancer. Your team needs skills in Linux, MongoDB replica sets, OpenSearch cluster operations, index lifecycle, TLS, backup and upgrades, plus detection engineering for the SIEM features. Confirm which of these skills exist in-house before you decide who operates the platform.

What drives the effort of a Sentinel to Graylog migration?

The effort is driven mainly by how many data sources you connect, how many analytics rules you must rewrite, and how much history you need to keep searchable. Each Microsoft data connector has to be replaced with a Graylog input such as syslog, GELF or Beats, or with a forwarder you configure. Each KQL analytics rule must be rebuilt as a Graylog event definition or pipeline rule, and each Logic Apps playbook needs a new home. Storage sizing matters too. Graylog's system architecture guidance advises sizing storage as daily ingest times retention days times 120 percent. Ask for an inventory of sources, rules and retention periods before any quote.

Is the Graylog Open license without caps enough for our SIEM?

It can be enough for log management and basic alerting, but it does not include the SIEM features that many security teams expect. Graylog Open is free to self-manage with no ingestion caps and community support. Graylog Security adds SIEM features such as risk scoring, anomaly detection, investigations, compliance packs and prebuilt threat detection content, and its pricing page lists a starting price of 18,000 US dollars per year with a minimum of 10 GB per day or 100 Graylog Compute Units. Graylog Enterprise adds the data lake, the correlation engine and 24/7 support. Note that Graylog Open is licensed under the Server Side Public License, which is not an OSI-approved license, so have legal review it.

How long should a parallel run with Sentinel last?

The length depends on the detection use cases you must prove and the retention period your compliance obligations require, not on a fixed rule. Run both platforms on the same log sources until each critical detection has fired and been triaged at least once in Graylog, and until your analysts trust the new searches. Sources with infrequent events, such as quarterly batch jobs or rarely used applications, need a longer window to generate comparable evidence. Agree on exit criteria in writing before the run begins, and confirm them with your SOC and compliance leads. Plan for the duplicate ingestion cost in Sentinel during this period.

What should a Graylog migration quote list?

A quote should list each deliverable in writing, tied to the scope you agree before work starts. Ask for the architecture, including Graylog nodes, MongoDB replica set, Data Node cluster, load balancer and sizing basis. Ask for an inventory of inputs, streams, processing pipelines, event definitions and dashboards to be rebuilt, plus the source-by-source cutover plan. Include backup and restore procedures, upgrade planning, hardening, documentation, and the parallel run exit criteria. Clarify what is one-time and what recurs, such as support, upgrades and continuous testing, and whether Graylog licensing is included or billed separately. DeployOpen does not publish a price list, so the quote follows from the written scope.

Does Graylog support Microsoft sources out of the box?

Graylog Open ingests logs over inputs such as syslog, GELF and Beats, so Microsoft sources are reached through those paths rather than through Sentinel's native connectors. Windows event data typically needs a shipping agent or collector that forwards to a Graylog input, and Azure or Microsoft 365 logs need an export or forwarding path that you design and test. Confirm the exact input, parser and content pack for each Microsoft source you need, because the pricing and product pages do not list a native connector for each one. Treat each source as a separate line item in your scope.

How does OpenSearch version support affect Graylog upgrades?

The OpenSearch version you run decides which Graylog releases you can upgrade to, so plan the backend version before you plan the Graylog version. According to Graylog's compatibility matrix, Graylog 7.0 to 7.2 support OpenSearch from 1.1.x up to 3.7.x, and Graylog Security needs OpenSearch 2.0 or later. Use of OpenSearch 1.x has been deprecated since Graylog 7.0 and will be removed in Graylog 8.0. If you deploy today, prefer Graylog's recommended Data Node as the search backend. Ask the vendor or your implementation partner to confirm the exact version pairing for your target release before you build the cluster.

How DeployOpen helps you evaluate, implement and migrate Graylog

DeployOpen plans, implements, hardens, documents and supports self-hosted open-source platforms inside your own cloud accounts, data centers or air-gapped networks. For Microsoft Sentinel vs Graylog, we start with a written scope that compares your current Sentinel ingestion, retention and detection workload against a Graylog design you can run yourself.

How we scope

Inventory current Sentinel data connectors, daily ingest volumes and retention periods by table or log source.
Define which Graylog edition, inputs, streams and event definitions the written scope will cover.
Agree deliverables, timelines and responsibilities in writing before any build work starts.

How we build

Deploy Graylog server nodes, MongoDB and Data Node or self-managed OpenSearch in your environment.
Configure syslog, GELF and Beats inputs, Sidecar collectors and processing pipelines for your sources.
Test index rotation, retention and alert notifications against sample and historical log data.

How we hand over

Document architecture, sizing assumptions, index retention settings and operational runbooks for your team.
Provide compliance evidence and control mapping so your auditors can review the implementation directly.
Train administrators on searches, dashboards, event definitions and upgrade procedures before handover.

How we support

Offer ongoing support, upgrades and continuous testing as a retainer after handover.
Plan Graylog version upgrades and OpenSearch compatibility checks against your own maintenance windows.
Confirm with Graylog which edition, support level and license terms apply to your environment.

Microsoft Sentinel vs Graylog