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Table of Contents

HSM at AWI

Hardware

Tape Library

TFin-E

The HSM (Hierarchical Storage Management) provides for your data

  1. unlimited storage space and
  2. two replicates on tape (in different buildings)
  3. a third copy on disk (for selected data, smaller files) → VTL (Silent Brick)

However, there are two caveats:

  1. Your Data is archived on a tape, so it will take a while to get it back (unless it is online or has a disk-copy).
  2. You need a project to archive your data (apply for a project here: eResources).


TFin-D

Frame #2 or Frame #3

← Live View →
User: viewer PW: Viewer123!

Frame #2 or Frame #3

Server and disks

  • Three Dell R760xd server ( hssrv2[a-c] )
  • 4 Brocade (32Gb) 6610 SAN switches
  • 270 TB SSD primary cache (Dell ME55084ME5084)
  • 488 TB Extended HDD-cache (Dell ME5084)
  • Ab Ende 2024:
    1120 TB Virtual Tape Library (VTL) Silent Brick von Fast-LTA 
    • Controller G5200
    • SAS Switch
    • 7x SilentBrick Max

Concept

Principle IdeaIdea 

  • HSM:  A (H)ierarchical (S)torage (M)anagement system consists of (at least) two storage systems: A cache speeds up access, and the hierarchy reduces cost. Based on a set of rules, data is stored on certain connected storage devices (tapes and optional disks).
  • ScoutFS is used at AWI since 2024 and supersedes samfs (used since decades before)  www.versity.com/products/scoutfs/  www.scoutfs.org . 
  • ScoutAM is used as (A)rchive (M)anager www.versity.com/products/scoutam/ and supersedes OHSM/ VSM

The Circle of Life

Archiving

  • When creating a file in ScoutFS (e.g., by rsync, scp, ftp, S3-PUT) the data is stored on a fast SSD cache system (SSD).
  • Depending on predefined policies (e.g., when the file has not been modified for a specific amount of time) the file is automatically archived on slower (and much cheaper) tapes (and optionally HDD).
  • A file just created is online

...

  • The metadata (filename, size, ownership, permissions, etc.) of a file remains always in the cache system and is visible/accessible, but 
  • when the cache system fills up (e.g, 90% capacity) the data of large files and files that have not been touched for some time is released.
  • If the data of the file is released it is called offline.
  • The user does (in the first instance) not see any difference between a an online and an offline file.

Staging

  • When offline data is accessed ScoutAM intercepts the call and automatically gathers the data from the archive media. ScoutAM uses information stored in metadata to find (any and stage = "copy back") the data.
  • In the meantime the reads read from this file is be blocked, thus the process accessing the data blocks is blocked, too.
  • When accessing more than a few files, prior staging is strongly recommended (see User commands)!

...

  • If the content of a file changes a new archive copy has to be produced. (You can not modify just the relevant bits on the tape.)
  • The previous archive copy becomes useless (aside from having an additional backup of a previous version).
  • If a file is deleted, the archive copy becomes useless, too.
  • Both processes result in unused (invalid) sections on a tape. 
  • Eventually only a small part of a tape contains relevant (up to date) information. The residual data is can be archived on other tapes, the old tape is erased and can be used for future archive copies. This process is called recycling.