Fortress

Overview of Fortress

The Fortress DXUL system is a large, long-term, multi-tiered file caching and storage system utilizing both online disk and robotic tape drives. Fortress was upgraded in the fall of 2006. It currently consists of an IBM p570 with four 1.65 GHz Power5 processors, 8 GB of RAM, and a 2.5 TB RAID disk cache with an effective capacity of 1.7 TB. Fortress also uses an ADIC Scalar 10K robotic tape library with a capacity of 1.2 PB (36 LTO-II drives and 2,000 LTO-II tape cartridges).

Detailed Hardware Specification

Storage Subsystem Drives Media Total Capacity Effective Capacity
RAID Disk Cache 2.5 TB 1.7 TB
ADIC Scalar 10k Robotic Tape Library 36 LTO-II 2,000 LTO-II 1.2 PB 600 TB

Files stored on Fortress are written to two separate storage devices. Recently used files smaller than 0.5 MB have their primary copy stored on 4TB of low-cost disks (disk cache), but the second copy (backup of disk cache) is on tape or optical disks. This provides a rapid restore time to the disk cache. However, the large latency to access a larger file (usually involving a copy from a tape cartridge) makes it unsuitable for use as active storage. The primary and secondary copies of larger files are stored on separate tape cartridges in the ADIC tape library.

In addition to poor performance, these two uses can cause severe problems with the system itself:

  • DO NOT store any actively used files on fortress.
  • DO NOT store large collections of small files on fortress.

Do not use fortress as a second home directory. Instead, use tar or some similar archive tool to combine all the smaller files you wish to store into a single large file first.

For active data storage you should use either local storage or a scratch file system. You may then copy any results you wish to archive to fortress when computation is complete.

Fortress runs AIX 5.2 and uses DXUL 2.9 from EMC.