1. CMS staging from tape Natalia Ratnikova, Fermilab
for WLCG pre-GDB Storage meeting
CERN, 12 September 2017

2. Outline CMS data organization Data transfers workflow
CMS storage sites topology
CMS local staging and transfers details
Staging tests status and work in progress
9/12/17
Natalia Ratnikova | WLCG pre-GDB Storage | CMS staging from tape

3. CMS data organization …
CMS data are organized into datasets by physics content
Dataset size varies: TB
Within a dataset, files are organized into blocks of 1–1000 for scalability
Small files are merged after processing to help scalability of storage and catalogs
Typical file size is ~ 2.5 G, but there are some quite large files
CMS data management tools can manipulate individual blocks as well as full dataset.
Data transfers are driven by subscribing datasets or blocks to the
Files …
Dataset
Blocks
9/12/17
Natalia Ratnikova | WLCG pre-GDB Storage | CMS staging from tape

4. Data transfers workflow
Powered by PhEDEx:
FTS3 Client
GFAL
Site Agents
9/12/17
Natalia Ratnikova | WLCG pre-GDB Storage | CMS staging from tape

5. CMS storage sites topology
CMS uses tape storage at 8 sites:
T0_CH_CERN
T1_US_FNAL
T1_DE_KIT
T1_RU_JINR
T1_ES_PIC
T1_IT_CNAF
T1_FR_CCIN2P3
T1_UK_RAL
During Run 1 CMS data needed for production at Tier-1 sites have been pre-staged manually by the site admins.
After Run1 all CMS Tier-1s sites deployed separate endpoints for disk and tape storage
Tape storage is used mainly for archiving purpose.
Data needed for production are subscribed to Disk by the production operators/tools.
9/12/17
Natalia Ratnikova | WLCG pre-GDB Storage | CMS staging from tape

6. CMS local staging and transfers details
Data are routed from the available sources to the destination, taking into account the link costs, performance and subscription priorities, using priority-window up to a fixed data volume.
Sites are using FTS3 as a transport layer to download the routed data.
T0/T1 sites run a special local Stager agent to check for data routed from MSS, call local plugins to stage the files and check the status, and mark the staged files as available for the download.
Routing, staging, and download are performed asynchronously.
9/12/17
Natalia Ratnikova | WLCG pre-GDB Storage | CMS staging from tape

7. Staging tests status and work in progress
Performed by CMS data operations to test the throughput between T1 MSS/Buffer abd T1 Disk end points
the throughput goals reached
too many tape mounts reported by the sites
fine tuning of the agents configuration to increase the number of staging requests and let MSS system to optimize
Triple increase of the router priority windows
adjustments on the MSS system side
experimenting with the stager idle time to create larger request volume
All detailed info is only in the local stager logs: experimenting with FTS3 staging to benefit from central monitoring.
9/12/17
Natalia Ratnikova | WLCG pre-GDB Storage | CMS staging from tape