Which fits better: Microsoft Sentinel or a self-run OpenSearch SIEM?
Sentinel fits best when most of your telemetry already lives in Azure and Microsoft 365, and your security team works in the Microsoft stack. Its built-in Microsoft data connectors, analytics rules and Defender XDR correlation remove much of the integration work. If your renewal or Azure portal retirement timeline is the trigger, note that after March 31, 2027 Sentinel is available only in the Microsoft Defender portal, where Defender XDR data privacy and retention policies replace Sentinel's own and the Fusion analytics rule is replaced by Defender XDR correlation. Confirm with Microsoft how that changes your retention and where your data is stored before you commit to staying.
A self-run OpenSearch SIEM fits when data location, retention ownership or licensing terms outweigh the convenience of a managed cloud service. OpenSearch is Apache 2.0 licensed, and the OpenSearch FAQ does not describe a paid edition. Security Analytics brings prepackaged, open source Sigma rules, detectors that apply rules to a chosen log type, findings generated on each match, alerts to channels such as email or Slack, and a correlation engine that links findings into threat scenarios. The trade-off is that your team owns the cluster, the sizing, the ingest pipelines, the upgrades and the detection tuning. Rules and retention are yours to set, but so is the effort to keep them running. Plan that capacity before you compare prices.
The decision turns on four questions. First, where your logs must physically reside and who may access them. Second, whether your team can operate a search cluster with on-call coverage, including OpenSearch's roughly eight-week minor release cadence and maintenance windows. Third, how much of your detection content already exists as Sentinel analytics rules that you would have to rewrite as Sigma. Fourth, your sign-in requirements: OpenSearch Security supports SAML and OpenID Connect, so confirm that your identity provider and role mapping meet your access model before you choose.
Which option fits each buyer scenario
This table lists common buyer situations and the platform that usually fits each one better, with the condition that makes the choice hold. Read each row against your own estate, and treat the conditions as the test to confirm before you decide. The main takeaway is that Sentinel fits Azure-centred, cloud-connected teams, while OpenSearch with Security Analytics fits teams that need to host the data and detections themselves.
| Scenario | Better fit | Why and the condition that holds it |
|---|---|---|
| Azure-only estate with Microsoft data sources | Microsoft Sentinel | Microsoft data connectors for Entra ID, Defender and Azure activity are built in. This holds while your sources are mostly Microsoft and you accept per-GB billing and Azure hosting. |
| Air-gapped or disconnected site | Self-run OpenSearch | Sentinel runs only in Azure and cannot be installed in an isolated network. OpenSearch can run inside the isolated network, provided you build the ingest path and update process offline. |
| Need for SAML or OpenID Connect sign-in to your own identity provider | Self-run OpenSearch | The OpenSearch Security plugin supports SAML and OpenID Connect. Confirm the exact role mapping and claims your identity provider sends before rollout. |
| Defender portal move already planned | Depends on retention needs | After March 31, 2027, Sentinel is available only in the Defender portal, where Defender XDR retention and privacy policies apply. OpenSearch fits if you want retention and access rules under your own control. |
| Team without Elasticsearch-style cluster operations | Microsoft Sentinel | Sentinel removes cluster sizing, shard management and upgrades from your team. This holds if no one on staff can own index lifecycle, rolling upgrades and node capacity. |
| Need to keep Sigma rules under version control | Self-run OpenSearch | Security Analytics starts from open source Sigma rules and lets you manage detectors in code. Confirm that your detector definitions can be exported and stored in your repository, as Sentinel analytics rules are exported as ARM templates. |
| Sentinel KQL analytics rules already in production | Depends on rewrite effort | Existing KQL detections must be translated to OpenSearch queries and Sigma-style rules. Choose OpenSearch when the rewrite is planned work and not a blocker for the cutover date. |
How Security Analytics detectors compare with Sentinel analytics rules
Both platforms turn ingested logs into alerts, but they package detection logic, findings and correlation differently. The four components below show where a Sentinel analytics rule maps to an OpenSearch detector, where the two diverge, and what your team must check before relying on either.
Sigma detectors and prepackaged rules
Security Analytics starts from prepackaged, open source Sigma rules. You attach rules to a detector for a chosen log type, so the rule library is the starting point rather than a finished detection program. A Sentinel analytics rule is a KQL query with its own schedule, entity mapping and incident settings. Migrating means translating each rule's logic and confirming that the Sigma rule for your log source behaves the same way on your data. Confirm current rule coverage for each log type you ingest.
Findings versus Sentinel incidents
In Security Analytics, a finding is generated each time a detector matches a rule against a log event, so volume follows raw matches. Sentinel groups alerts into incidents that analysts triage and assign. OpenSearch gives you findings as indexed documents you can query and dashboard, but grouping, ownership and case handling are not built in the way they are in Sentinel. Ask your SOC how many findings per day a noisy rule produces and who owns deduplication before go-live.
Alert notifications and playbooks
Security Analytics alerts can notify channels such as email or Slack when a detector matches one or more rules. Sentinel alerting is tied to incidents and can trigger Logic Apps playbooks for enrichment, ticketing and response. In OpenSearch, notification channels cover the alert path, but response automation is a separate design decision, often handled by an orchestration tool. Map each Sentinel playbook to a named owner and confirm which notifications your team needs before cutover.
Correlation rules and the graph
The correlation engine links findings from different log types into threat scenarios and shows them in a correlation graph. Sentinel's equivalent in the Defender portal is Defender XDR correlation, which replaces the Fusion analytics rule. The two work from different data models, so a multi-stage scenario in Sentinel will not map one to one onto OpenSearch correlation rules. Test each cross-source scenario against your real logs and confirm that the correlation graph shows the entities your analysts need.
Capability by capability: Sentinel and OpenSearch Security Analytics
This table compares licensing, detection content, correlation, sign-in, access control, audit and platform direction for Microsoft Sentinel and OpenSearch with Security Analytics. Where a supplied source does not settle a point, the cell tells you what to confirm with the vendor or in your own test environment. Use it to find the gaps you need to plan around before you commit to a migration.
| Capability | Microsoft Sentinel | OpenSearch with Security Analytics |
|---|---|---|
| Licensing and cost model | Billed through Azure, with per-GB analytics tier and retention charges | Apache License 2.0; the OpenSearch FAQ describes no paid edition, but you pay for servers, storage and staff |
| Detection content | Analytics rules, with Microsoft-supplied content in the Azure portal or Defender portal | Prepackaged open source Sigma rules applied by detectors to a chosen log type |
| Findings and alerts | Incidents and alerts in the Sentinel workspace, moving to the Defender portal | A finding is generated each time a detector matches a rule; alerts can notify email or Slack channels |
| Correlation | Fusion analytics rule in the Azure portal; replaced by Defender XDR correlation in the Defender portal | Correlation engine links findings across log types into threat scenarios shown in a correlation graph |
| SAML and OpenID Connect sign-in | Azure Entra ID sign-in; confirm other federation options with Microsoft | Security plugin supports SAML and OpenID Connect, plus Active Directory, LDAP, Kerberos and JWT |
| Role-based access control | Azure role-based access control at workspace and resource level; confirm granularity with Microsoft | Role-based access control with document-level and field-level security and field masking |
| Audit logs | Azure activity and workspace audit records; confirm which events reach your retention store | Audit logs available through the Security plugin; confirm the event categories you need |
| Platform direction | Azure portal support ends after March 31, 2027; Defender portal only; moving has no extra cost per Microsoft | Open source project with minor releases about every eight weeks; confirm your upgrade path with the OpenSearch project |
| Query and API compatibility | KQL in Log Analytics and the Sentinel API | Wire-compatible with Elasticsearch 7.10 REST APIs; confirm client libraries and query behavior in testing |
Microsoft data connectors against ingest pipelines you build
Microsoft Sentinel ships with data connectors for Microsoft sources and a large catalog of partner sources, so most onboarding is configuration: you select a connector, grant it the required permissions and choose which tables receive the data. With OpenSearch, that work moves to your team or a partner. Each source needs a collector such as Fluent Bit, Logstash or the OpenTelemetry Collector, a parser that turns raw events into fields, a field mapping that matches your index templates and an index design that handles retention and volume. None of that is included in the OpenSearch install, and all of it must be maintained when a source changes its log format.
The balance depends on your estate. A heavy Microsoft 365 and Azure environment, with Entra ID, Defender and Azure activity logs as the main sources, favors Sentinel, because the connectors already map those tables and the detection content is written against them. A mixed estate with on-premises Windows servers, network appliances, mainframe or OT systems, and custom application formats raises the build effort on the OpenSearch side, and the same is true if many of those sources have no ready parser. Each custom format becomes a parser you write, test and own. Before you decide, inventory every log source, its event volume, its format and its owner. For each one, confirm whether an existing collector and parser covers it, which Sigma log sources it maps to and which fields the detectors need. Ask the OpenSearch partner or your own engineers to document this as a coverage table, and treat any source without a confirmed parser as a line item in the migration scope, not a detail for later.
Where your logs live and who can read them
Logs carry the most sensitive view of an environment, so where they are stored, how the platform is hosted and who can sign in matter as much as detection quality. The four cards below compare Microsoft Sentinel and a self-run OpenSearch cluster on those points and name the decisions each one forces.
Data location and operator
Sentinel stores workspace data in the Azure region you select and the service is operated by Microsoft. With OpenSearch, the indices, snapshots and backups sit in the data center or cloud account you choose, and your team operates the nodes. Confirm which Azure region your Log Analytics workspace uses, which regions your backup targets use, and whether any log types leave your chosen boundary through connectors or exports.
Hosting model and install paths
OpenSearch is a self-managed deployment that you install with Docker, Helm, the OpenSearch Kubernetes Operator, a tarball, RPM or Debian packages, an Ansible playbook or on Windows. Each path changes who patches the operating system, who rotates certificates and who restores snapshots. Sentinel removes that layer, but you give up control over where the service runs and when its changes land.
Sign-in and directory backends
The OpenSearch Security plugin supports SAML, OpenID Connect, Active Directory, LDAP, Kerberos and JSON Web Token backends, so you can map existing identity providers to cluster roles. Sentinel relies on Microsoft Entra ID and Azure role assignments. In the Defender portal, Defender XDR privacy and retention policies apply to the data instead of Sentinel's own settings, which changes who approves retention and access. Confirm the group-to-role mapping for each option before cutover.
Audit trail and compliance evidence
On OpenSearch, you own the audit logs, role-based and field-level access settings and the TLS configuration for node and client traffic, so each control needs a configuration file, a test result and a log sample to show an assessor. Sentinel evidence comes from Azure activity and Microsoft service documentation. DeployOpen prepares systems, controls and evidence for compliance assessments, but it does not issue audit reports; an independent auditor or certification body decides whether the controls meet the standard.
What drives the cost on each side
Microsoft Sentinel is billed through Azure, so most of its cost follows the volume of data you ingest and how long you keep it. Analytics tier ingestion is charged per gigabyte, and commitment tiers can lower the unit rate when you commit to a daily volume. Retention beyond the included period is a separate recurring charge, and export to storage or other destinations carries its own charges. Confirm the current rates in the Azure pricing calculator for your region, because these change and are not set out here.
- Analytics tier ingestion: Recurring and driven by gigabytes ingested. Filtering noisy sources before they reach the workspace is the most direct lever.
- Commitment tiers: Recurring. They reduce the per-gigabyte rate only if your daily volume is stable enough to commit to.
- Retention charges: Recurring and driven by how many days you keep data beyond the included period, and by the tier the data sits in.
- Export charges: Charged when you move data out for long-term archive or migration. Plan these during an exit, not after.
- Defender portal move: Microsoft says moving to the Defender portal has no extra cost. The cost change is in policy, since Defender XDR data privacy and retention policies then apply instead of Sentinel's.
Ask the Microsoft account team or a partner for a quote that shows ingestion, commitment tier, retention and export as separate lines, using your last twelve months of actual volume by source. Ask which charges apply in the Defender portal and whether any Defender XDR licensing is required for your use case.
Self-hosting OpenSearch moves cost from a metered service to resources you buy and staff you assign. OpenSearch is released under the Apache License, Version 2.0, and the OpenSearch FAQ does not describe a paid edition, so there is no software licence fee for the core product. The recurring costs are the compute, storage, network, people and support needed to keep the cluster healthy, and they scale with your data volume and retention period.
- Software licensing: No fee for Apache 2.0 software. Budget for any third-party support contract you choose to buy separately.
- Servers and storage: Recurring or refreshed on a hardware cycle. Storage sized for retention is usually the largest driver, so retention period and replica count set the footprint.
- Network: Recurring and driven by cross-zone or cross-site traffic and by log shipping volume from sources.
- Staff time: Recurring. Operating the cluster, tuning shards, handling upgrades and reviewing Sigma-based detectors all take people. OpenSearch targets a new minor version about every eight weeks, so plan for regular upgrade work and maintenance windows, and note that versions in maintenance receive fixes and security patches but no new features.
- Backup and support: Backup storage recurs. Vendor or partner support is optional and priced on written scope.
When requesting quotes, ask for the staffing model in hours per month, the storage calculation with retention and replicas, and the upgrade and patch approach. DeployOpen quotes follow a written scope agreed before work starts, so the scope should state the environment, the data volume, the retention period and the support hours.
SAML or OpenID Connect sign-in for analysts
Analysts reach Microsoft Sentinel through Microsoft Entra identity, so a team already on an Entra tenant signs in with the accounts, conditional access policies and multifactor settings it already runs. Sentinel access is then governed by Azure role-based access control on the workspace and, once the workspace moves to the Microsoft Defender portal, by the Defender XDR role model. OpenSearch works differently. The Security plugin can federate sign-in with SAML or OpenID Connect providers, and it can also use Active Directory, LDAP, Kerberos or JSON Web Token backends. Analyst permissions are then set inside OpenSearch Security through roles and role mappings, which tie identity provider groups or claims to the roles that control index, dashboard and Security Analytics access. The choice matters most in two cases: when the organization already runs Entra and wants one sign-in path for analysts, which favors keeping Sentinel's identity model, and when the SOC uses an external IdP or a non-Microsoft directory, which makes OpenSearch federation the natural fit.
The operating effort sits in the mappings, not the initial login. Every OpenSearch role mapping has to be kept in step with the identity provider's group names, claim values and the roles that analysts, detection engineers and administrators actually need, and every change to an analyst's group membership in the provider must flow through to OpenSearch without leaving stale access. Joiner, mover and leaver processes, and the review of who holds Security Analytics or administrative roles, become part of the SOC's routine work. Sentinel carries a similar job in Entra groups and Azure role assignments, but the mapping layer is different in each case. Before committing, confirm with your identity team the exact claim, such as the group or role claim your provider emits in SAML assertions or OpenID Connect tokens, and the group identifiers the mappings should match, and test sign-in with a non-administrative analyst account. Confirm the current federation steps for your OpenSearch version in the OpenSearch security documentation before writing role mappings.
What a move from Sentinel to OpenSearch involves
The sequence turns Sentinel's ingestion, detections and access model into a self-run OpenSearch cluster with Security Analytics, and ends with Sentinel switched off only after both platforms have been checked side by side. Each step leaves a written output that the next one depends on.
Inventory data sources and detections
Your team lists every Sentinel data connector, table, analytics rule, scheduled query, workbook and saved hunting query, along with the owner, log volume and the systems that consume each alert. DeployOpen can run this inventory with your security engineers when it is part of a fixed-scope engagement. The step is done when each source and detection has a named owner and a target decision: keep, rewrite as a Sigma-based detector, or retire.
Stand up a sized OpenSearch cluster
Platform engineers size the cluster from the daily ingest volume, retention periods and query load recorded in the inventory, then deploy OpenSearch with one of the documented install methods, such as Docker, Helm, the Kubernetes Operator or packages. Security Analytics is enabled, TLS is configured for node and client traffic, and role-based access is defined before any log reaches the cluster. The step is done when a test index can be written and read by a restricted analyst account and an administrator account, and the cluster health checks pass in your environment.
Connect sign-in and access controls
Identity engineers configure the OpenSearch Security plugin with your existing identity provider using SAML or OpenID Connect, then map groups to roles that control index access, document-level and field-level security, and field masking for personal data. Audit logging is switched on so access to security data is itself recorded. The step is done when a test analyst can sign in through the identity provider, sees only the indices granted to that role, and the access attempts appear in the audit log.
Build ingest pipelines and index mappings
Engineers replace each Microsoft data connector with an ingest path you operate, such as agents, syslog collectors or pipeline tools that write to OpenSearch. They define index templates and field mappings so that normalized fields used by Sigma rules, such as user, host and process names, are consistent across sources. The step is done when each source delivers events into a named index, sample events match the expected mapping, and the field names used by the detection rules resolve correctly.
Export or replay history where retention requires it
Where regulation, an open investigation or a retention commitment requires older data, the team exports Sentinel history and loads it into dated indices. The export method, file format and loading steps are set out in the sibling Sentinel export and migration pages. Your compliance lead confirms which periods must be kept, in which form, and who approves the copy. The step is done when a sampled set of exported records matches row counts and key fields in the source, and the approver signs off the retained scope.
Translate analytics rules and hunting queries
Detection engineers convert each retained analytics rule into a Sigma-based detector within Security Analytics, using the open source Sigma rules as a starting point where they fit, and write correlation rules for multi-source scenarios that Sentinel handled through its own rule logic. KQL hunting queries and workbooks have to be rewritten in OpenSearch query syntax and dashboards, which is manual work and should be scoped explicitly in the plan. Alert routing to email or chat channels is rebuilt at the same time. The step is done when each detector has a documented test event, a known-good result and an owner, and any rule that cannot be translated is logged as an accepted gap.
Run both platforms in parallel
For a validation window agreed in writing, both Sentinel and the OpenSearch cluster receive the same sources. Analysts compare the alerts each platform raises for the same activity, measure missed detections and noisy rules, and tune thresholds. Your change board records each difference and its resolution. The step is done when every planned detection has either matched in the parallel run or has an accepted exception, and the analysts have signed off that they can investigate alerts in the new platform.
Cut over sources, analysts and decommission Sentinel
Sources are repointed one group at a time to OpenSearch, analysts move their on-call and investigation routines, and the old connectors are disabled in a controlled order. Once the retention and audit obligations are met and the copies are verified, the Sentinel workspace, data connectors and related Azure resources are removed according to your own decommissioning procedure. The step is done when no source still sends to Sentinel, the final export is stored in your retention location, and the decommissioning record is filed with the security and compliance owners.
Questions buyers ask before choosing OpenSearch or Sentinel
What does moving from Microsoft Sentinel to OpenSearch cost?
The cost is a mix of one-time project work and recurring run costs, and the balance depends on your environment. On the Sentinel side, the recurring bill is driven by ingested gigabytes, the analytics tier you pay for, and how long you keep data beyond the included period. On the OpenSearch side, you pay for compute, storage, network, backups, and the staff time to operate the cluster, plus any implementation partner fees. OpenSearch itself is Apache 2.0 licensed, so there is no software license line item. Ask any provider for a written quote that separates one-time migration work (connector rebuilds, detection rewrites, sizing, hardening) from recurring hosting and support, and state the daily volume and retention period the quote assumes.
How long does an OpenSearch migration from Sentinel take?
The timeline is set by the number of data sources, the volume of detection content to rebuild, the retention and history you need to carry over, and how many environments must be cut over. Teams with a small set of connectors and a limited rule library usually have a shorter path than teams with many custom analytics rules, workbooks and playbooks. Parallel running during cutover adds time but reduces risk. Compliance evidence collection and approval cycles also add weeks that are unrelated to the technical work. No duration is safe to plan on until the scope is written down, so ask for a fixed-scope plan with milestones and named dependencies before you commit a date.
What does my team need to provide during a Sentinel to OpenSearch project?
Your team needs to supply access, decisions and knowledge that only you hold. This includes an inventory of log sources and their owners, the current analytics rules and their business purpose, a list of who uses the workbooks and dashboards, network paths from sources to the new ingest tier, identity provider configuration for SAML or OpenID Connect sign-in, and approval for retention and data residency choices. Your security analysts will need to review rebuilt detections and confirm that alert routing still reaches the right people. Agree these responsibilities in the written scope so that delays on either side are visible early.
Can our own team run OpenSearch Security Analytics without outside help?
A capable platform team can run Security Analytics, but the work is more than installing a plugin. OpenSearch Security Analytics uses prepackaged, open source Sigma rules as a starting point, and a detector applies rules to a chosen log type, generating a finding each time a rule matches a log event. Your analysts still need to tune rules, decide which findings become alerts, and write correlation rules that link findings across log types into threat scenarios. Those skills, along with cluster sizing, index lifecycle management, upgrades and backups, are ongoing responsibilities. Many teams start with a short external review of their architecture and detection content, then run the platform in-house. Confirm your staffing against the operations scope before deciding.
Does OpenSearch have a paid edition?
The OpenSearch FAQ does not describe any paid edition. All software in the OpenSearch project is released under the Apache License, Version 2.0, and the project is governed by the OpenSearch Software Foundation, a Linux Foundation project. That foundation is not involved in the technical oversight of the project. Cost questions therefore concern infrastructure, operations and services, not a license tier. If a vendor offers a commercial distribution or managed service built on OpenSearch, treat it as a separate product with its own terms and confirm those terms in writing. Check the OpenSearch FAQ and the license files in the release you deploy before making a purchasing decision.
Does Sentinel retirement from the Azure portal force a decision?
Yes, it creates a decision point, but not an immediate one. After March 31, 2027, Microsoft Sentinel will no longer be supported in the Azure portal and will be available only in the Microsoft Defender portal. Microsoft says the move to the Defender portal has no extra cost. Once Sentinel runs in the Defender portal, Microsoft Defender XDR data privacy and retention policies apply instead of Sentinel's, and the Fusion analytics rule is replaced by Defender XDR correlation. Teams that stay on Sentinel must re-validate their detections and retention under those policies. Teams considering OpenSearch should plan their exit early enough to test detection parity before the date. Review the Defender portal transition guidance with your Microsoft contact.
Can OpenSearch alone make us pass an audit?
No. A platform, including OpenSearch, provides technical controls such as role-based access control, document and field-level security, audit logs and TLS, but it does not establish compliance on its own. Audit outcomes depend on how the system is configured, operated, documented and evidenced across the whole control set. DeployOpen prepares systems, controls and evidence for compliance assessments, but it does not issue audit reports, attestations or certifications. Independent auditors and certification bodies perform those assessments. Ask the implementation provider which controls its scope covers and which evidence it will deliver, and confirm with your auditor which requirements apply to your organization.
How DeployOpen helps evaluate, implement or migrate
DeployOpen plans, implements, integrates, hardens, documents and supports self-hosted open-source platforms inside your own cloud accounts, data centers or air-gapped networks. For Microsoft Sentinel vs OpenSearch, that means starting from your current Sentinel analytics rules, data connectors and retention needs, then building a Security Analytics environment you can run, test and hand over.
How we scope
- Inventory the Sentinel data connectors, analytics rules and retention settings that the OpenSearch cluster must replace or match.
- Agree in writing which log sources, detectors, Sigma rule sets, alert channels and correlation rules are in scope.
- Define sizing inputs, including daily ingest, retention periods and index lifecycle needs, so infrastructure can be estimated from your data.
How we build
- Deploy the OpenSearch cluster and Security Analytics plugin in your environment using a documented installation method you select.
- Build ingest pipelines for each log type, then map sign-in through SAML or OpenID Connect to your existing identity provider.
- Test detectors against sample events, tune Sigma rules that produce noise, and document the findings and alert paths for review.
How we hand over
- Deliver architecture, configuration, role and access settings, and detector inventories written for your security and platform teams.
- Run a handover session covering how findings are triaged, how alerts reach email or Slack, and how the correlation graph is read.
- Provide runbooks for upgrades, backups and rolling version changes so your staff can maintain the cluster after the engagement ends.
How we support
- Engagements are fixed-scope, with scope, deliverables and timelines agreed in writing before work starts.
- Ongoing support, OpenSearch upgrades and continuous security testing of the cluster are available as a retainer.
- Ask for a quote built from the written scope, and confirm which support tasks and response arrangements it includes.
