# Presentation: 548837

## DFS Replacement

- James Goodwin

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## Overview

**Timeframe**
**Sunsetting DFS**
**HPSS File System (VFS)**
**Remote Access Methods**

## Timeframe

**DFS end of life is in 2Q2006**
**Replacement is part of HPSS 6.2 release**
**Allows several months for existing sites to convert**

## Sunsetting DFS

**Two existing customers use DFS: IU & KEK**
**High-level plan:**
- Set up access to existing data using HPSS file system
- Set up remote access mechanism (NFSv4, Samba, etc.)
- Move existing DFS data & namespace into HPSS
- First, convert archived filesets
- Second, convert mirrored filesets

## Sunsetting DFS

**Very few archived filesets in production**
**For the few archived filesets**
- HPSS namespace is not human-readable
- Not all DFS files are large enough to have migrated to HPSS
- So conversion steps are:
- Establish remote HPSS file system access to a DFS client node
- Use traditional UNIX commands to copy archived filesets into HPSS (i.e., “**cp –Rph <DFS dir> <HPSS dir>**”)

## Sunsetting DFS

**Both IU & KEK heavily use mirrored filesets**
**Entire namespace is already duplicated in HPSS**
**Since data in HPSS may not all be current, steps are:**
- Disable client access to DFS interfaces
- Update migration policies to migrate everything
- Force migration and verify all data has moved
- Change mirrored filesets to HPSS-only
- Delete DMG portion of fileset metadata (can be done later)

## HPSS File System (VFS)

**A DFS replacement needs to provide access to HPSS namespace and data using a POSIX file system interface**
**The HPSS File System accomplishes this by using the VFS abstraction to make HPSS appear as any another Linux file system**
**Applications built to work with other Linux file systems can port directly without the need to recompile**

## HPSS File System (VFS)

**How to use it**
- Install the HPSS File System software on a node with a Linux 2.6 kernel
- Load the hpssfs kernel module (can be automatic)
- Mount the HPSS namespace using the mount command with a ‘-t hpssfs’ option
- Access HPSS at the mount point as any other file system

## HPSS File System (VFS)

**How it works**
- Kernel module
- implements VFS interface
- fields client requests
- performs I/O to and from HPSS Movers
- User space daemon
- communicates with HPSS using Client API
- authenticates as trusted principal
- uses hpss_ReadList() and hpss_WriteList() to initiate data transfers
- COS determined
- by COS or size hints set using ioctl()
- by mount option
- by default COS defined for subsystem or in global config

## HPSS File System (VFS)

## Remote Access Methods

**The HPSS File System’s userspace daemon must authenticate as a trusted principal**
**This involves the use of a Kerberos keytab file, which could also be used by a system admin to authenticate as a trusted principal**
**To maintain security, it is necessary that the HPSS File System only be executed on machines where root access is controlled (e.g., those in an access-restricted lab)**
**Remote access methods are required to allow client access**

## Remote Access Methods

**NFSv4 provides Kerberos authentication and is  the most secure remote access method**
**The NFSv4 Daemon exports the HPSS File System mount point**
**RedHat EL 4 supports both NFSv4 clients and servers**

## Remote Access Methods

## Remote Access Methods

**Users will ‘kinit’ on the client machine**
**NFSv4 Daemon will verify principal with Kerberos**
**Principal name will be cross-referenced by NFS identity mapper (usually using local password file) to determine user ID**
**User ID used in request to HPSS File System**
**HPSS File System is a trusted principal, so HPSS accepts that the request is on behalf of User ID**

## Remote Access Methods

**NFSv4 clients currently available for**
- RHEL 4
- AIX 5.3
- Windows (from Hummingbird)
**Users not requiring Kerberos can use alternative export mechanisms**
- Samba
- NFS 2/3

## Questions?