IBM TotalStorage DS6000 Series: Performance Monitoring and Tuning

326 IBM TotalStorage DS6000 Series: Performance Monitoring and Tuning

Servers with more than 16 GB of physical memory should not use both the /3GB switch and

the /PAE switch. The /PAE switch is obviously required to make use of all physical memory

above 4 GB. Remember that PAE uses the kernel addressable memory to manage the

physical memory above 4 GB. When physical memory exceeds 16 GB, the 1 GB of memory

allocated to the kernel when the /3GB switch is used is not sufficient to manage all of the

additional physical memory above 4 GB. Thus, only the /PAE switch should be used in such a

case to avoid the system running out of kernel memory.

9.3 File system overview

A file system is a part of the operating system that determines how files are named, stored,

and organized on a volume. A file system manages files and folders, and the information

needed to locate and access these items by local and remote users. Microsoft Windows

Server 2003 and Windows 2000 support both the FAT and NTFS file systems.

FAT The File Allocation Table (FAT) file system is the original file system introduced by

Microsoft. FAT was designed for small disks and a simple directory structure. The

maximum drive size using FAT is 2 GB. FAT and FAT32 do not have any file or folder

security. Therefore the server does not have to check the permissions on an

individual file when it is accessed by users. For performance reasons, it is

recommended that FAT be used on drives that will be less than 400 MB.

FAT32 FAT32 is a newer, improved version of FAT. FAT32 allows you to format a disk that is

greater than 2 GB. It also uses smaller clusters than the FAT. This saves disk drive

space on large drives by being able to store data more efficiently.

NTFS NTFS uses a B-tree structure. This type of structure improves performance by

minimizing the number of times the disk is accessed, which makes it faster than the

FAT.

NTFS is always be the file system of choice for servers. NTFS offers considerable

performance benefits over the FAT and FAT32 file systems and should be used exclusively on

Window servers. In addition, NTFS offers many security, scalability, stability and reliability

benefits over FAT.

Under previous versions of Windows, FAT and FAT32 was often implemented for smaller

volumes (say < 400 MB) as they were often faster in such situations. With disk storage

relatively inexpensive today and operating systems and applications pushing drive capacity to

a maximum it is unlikely that such small volumes will be warranted. FAT32 scales better than

FAT on larger volumes but is still not an appropriate file system for Windows servers.

FAT and FAT32 have often been implemented in the past as they were seen as more easily

recoverable and manageable with native DOS tools in the event of a problem with a volume.

Today, with the various NTFS recoverability tools built both natively into the operating system

and as third-party utilities available, there should no longer be a valid argument for not using

NTFS for file systems.

9.3.1 NTFS overview

NTFS is a journaling file system that enables fast file recovery. Journaling file systems are

based on the transaction processing concepts found in database theory. Internally, it more

resembles a relational database than a traditional file system. It is comparable in function to

the Veritas file system found on some UNIX implementations.

NTFS was designed to provide reliability, security, and fault tolerance through data

redundancy. In addition, support was built into NTFS for large files and disks, Unicode-based