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.