DCache summary

DCache is a high throughput, medium latency file system, supporting several protocols
  • dcap
  • ftp ( password, kerberized, grid )
  • nfs 4.1
  • webdav
  • xrootd

Files cannot be modified or appended.

Backed up by tape via Enstore by default.
SFA (Small File Aggregation) allows efficient tape storage of small files.
/pnfs/*/scratch areas are not backed up to tape, for volatile files.

Clients connect to doors which redirect data to the pools hosting the files.
Pools self-regulate activity to acceptable levels, when properly adjusted.

File directory performance has improved with DCache 2.6
Directory operations require access to a backend database.
  • 2.2
    • ls about 100/second
    • ls -l about 10/second
  • 2.6
    • ls about 5000/second
    • ls -l about 2000/second
Overall throughput can be 1 GByte/sec per pool host
  • readWritePools - 17 hosts
  • PublicScratch - 9 hosts

What is the network link capacity between DCache and GPGrid ?