FSLogix
Microsoft’s profile container technology for multi-session Windows environments. It solves the old problem of loading user profiles fast enough in non-persistent VDI — and is the standard on AVD today.
What is FSLogix?
FSLogix is a profile container solution for Windows environments. Instead of storing user profiles in a local directory or a classic roaming profile, FSLogix places each profile in its own VHDX file on a file share.
At sign-in FSLogix mounts the VHDX as a virtual drive and links it directly to the user profile path. The profile appears as if it were local — with all applications, settings, the Outlook cache and OneDrive sync.
The core problem FSLogix solves: in multi-session or non-persistent VDI, users have no VM of their own. The classic Windows profile has to be assembled at every sign-in — Outlook has no cache, Teams has to set itself up again, settings are gone. FSLogix makes profiles portable.
The two container types in FSLogix
| Container type | What is in it? | Use |
|---|---|---|
| Profile Container | The complete Windows profile: desktop, documents, AppData, parts of the registry | The standard — used in almost every case |
| Office/ODFC Container | Only the Office cache: OST, search index, Teams cache | Used separately for performance tuning, or when the profile container is managed by another tool |
Most setups use only the Profile Container — it is comprehensive and easier to manage. Using the ODFC container separately is a specialist scenario.
Where are the VHDX profiles stored?
FSLogix needs an SMB file share with high IOPS capacity. The options in Azure:
| Storage option | Performance | Price | Recommendation |
|---|---|---|---|
| Azure Files Premium | Very good (up to 100k IOPS) | ~€0.25/GB/month | The standard recommendation |
| Azure NetApp Files | Enterprise grade (up to 500k IOPS) | Expensive (~€0.30-0.50/GB) | For large enterprise setups |
| Azure Files Standard | Adequate for small setups | ~€0.05/GB/month | Only for proofs of concept and smaller businesses |
| Self-managed Windows File Server | Variable | VM + Disks | Hybrid scenarios |
Sizing rule of thumb
~30 GB per user is a good starting point (profile, Outlook cache, Teams cache, downloads). For 100 users that means reserving around 3 TB of storage — and budgeting for growth to 5 TB.
Optimising FSLogix sign-in time
The biggest FSLogix optimisation is the Sign-in time. The target: under 10 seconds from sign-in to desktop.
Best practices
- Azure Files Premium or NetApp Files (not standard SSD)
- Storage in the same Azure region as the session hosts (low latency)
- Size Quota on the VHDX (30 GB, for example) — it stops profiles from exploding
- Cloud Cache for multi-region: local read cache copies for fast sign-in
- Redirections.xml — excluding certain folders (OneDrive, Pictures) from the profile
- Install Office apps in shared activation mode (it reduces profile size)
The most common performance killer: Outlook OST files that grow without limit. One heavy user with a 20 GB Outlook cache makes every sign-in unbearable. The fix: set an OST size limit by group policy (5 GB maximum), or disable cached mode.
FSLogix licensing
FSLogix is included at no extra cost in the following licences:
- Microsoft 365 E3, E5, A3, A5, F3
- Microsoft 365 Business Premium
- Windows 10/11 Enterprise E3, E5
- RDS CALs
- Windows Server RDS
There are no separate FSLogix licences any more (Microsoft has integrated it). Anyone holding one of these licences may use FSLogix at no additional cost.
FSLogix-Patterns in DaaS Maps
DaaS Maps shows FSLogix configurations and storage options in detail. For performance tuning and FSLogix troubleshooting, you will find me on LinkedIn.