MLP storage advice (#145)

Author: rubber-duck-debug

docs/platforms/mlp/index.md

@@ -35,8 +35,9 @@ There are three main file systems mounted on the MLP clusters Clariden and Brist
 
 | type |mount | filesystem |
 | -- | -- | -- |
-| Home | /users/$USER | [VAST][ref-alps-vast] |
+| Home | `/users/$USER` | [VAST][ref-alps-vast] |
 | Scratch | `/iopsstor/scratch/cscs/$USER` | [Iopsstor][ref-alps-iopsstor] |
+|         | `/capstor/scratch/cscs/$USER` | [Capstor][ref-alps-capstor] |
 | Project | `/capstor/store/cscs/swissai/<project>` | [Capstor][ref-alps-capstor] |
 
 ### Home
@@ -51,14 +52,31 @@ Use scratch to store datasets that will be accessed by jobs, and for job output.
 Scratch is per user - each user gets separate scratch path and quota.
 
 * The environment variable `SCRATCH=/iopsstor/scratch/cscs/$USER` is set automatically when you log into the system, and can be used as a shortcut to access scratch.
+* There is an additional scratch path mounted on [Capstor][ref-alps-capstor] at `/capstor/scratch/cscs/$USER`. 
 
 !!! warning "scratch cleanup policy"
     Files that have not been accessed in 30 days are automatically deleted.
 
     **Scratch is not intended for permanent storage**: transfer files back to the capstor project storage after job runs.
 
-!!! note
-    There is an additional scratch path mounted on [Capstor][ref-alps-capstor] at `/capstor/scratch/cscs/$USER`, however this is not recommended for ML workloads for performance reasons.
+!!! note "file system suitability"
+    The Capstor scratch filesystem is based on HDDs and is optimized for large, sequential read and write operations.
+    We recommend using Capstor for storing **checkpoint files** and other **large, contiguous outputs** generated by your training runs.
+    In contrast, Iopstor uses high-performance NVMe drives, which excel at handling **IOPS-intensive workloads** involving frequent, random access. This makes it a better choice for storing **training datasets**, especially when accessed randomly during machine learning training.
+
+### Scratch Usage Recommendations
+
+Use Iopstor scratch (`$SCRATCH`) for:
+
+* Training and validation datasets that are read frequently and non-sequentially.
+* Workloads that perform many small, random I/O operations.
+
+Use Capstor scratch (`/capstor/scratch/cscs/$USER`) for:
+
+* Storing model checkpoints.
+* Outputs from simulations or training jobs that involve large, contiguous I/O.
+
+After your job completes, remember to transfer any important results to your permanent project storage.
 
 ### Project