IBM TotalStorage DS6000 Series: Performance Monitoring and Tuning

328 IBM TotalStorage DS6000 Series: Performance Monitoring and Tuning

where a large number of files and directories are accessed quickly and in a short period of

time, such as by a backup application. Apart from in highly secure environments, retaining

this information may be adding a burden to a server that can be avoided by updating the

following registry key:

HKLM\SYSTEM \CurrentControlSet \Control \FileSystem

NTFSDisableLastAccessUpdate

Change its value from 0 to 1. For more information, see:

http://www.microsoft.com/resources/documentation/WindowsServ/2003/all/deployguide/en-us/466

56.asp

In Windows Server 2003, this parameter can also be set by using the command:

fsutil behavior set disablelastaccess 1

Reliability

To ensure reliability of NTFS, three major areas were addressed: Recoverability, removal of

fatal single sector failures, and hot fixing.

The recoverability designed into NTFS is such that a user should never have to run any sort of

disk repair utility on an NTFS partition. This is because NTFS uses a journaled log to keep

track of transactions made against the file system. When a CHKDSK is performed on a FAT

file system, the consistency of pointers within the directory, allocation, and file tables is being

checked. Under NTFS, because a log of transactions against these components is

maintained, CHKDSK need only roll back transactions to the last commit point in order to

recover consistency within the file system.

Under FAT, if a sector that is the location of one of the file system's special objects fails, then

a single sector failure will occur. NTFS avoids this in two ways. First, by not using special

objects on the disk and tracking and protecting all objects that are on the disk. Second, under

NTFS, multiple copies (the number depends on the volume size) of the Master File Table are

kept.

Similar to OS/2® versions of HPFS, NTFS supports hot fixing. NTFS will attempt to move the

data in a damaged cluster to a new location in a fashion that is transparent to the user. The

damaged cluster is then marked as unusable. Unfortunately, it is possible depending on what

damage has occurred, that the moved data may be unusable.

9.3.4 Added functionality

NTFS fully supports the Windows NT security model and supports multiple data streams. No

longer is a data file a single stream of data. Additionally, under NTFS, a user can add his or

her own user-defined attributes to a file.

9.3.5 Removing limitations

First, NTFS has greatly increased the size of files and volumes so that they can now be up to

2

64

bytes (16 exabytes). NTFS has also returned to the FAT concept of clusters in order to

avoid the HPFS problem of a fixed sector size. This was done because Windows Server 2003

is a portable operating system and different disk technology is likely to be encountered at

some point. Therefore, 512 bytes per sector was viewed as having a large possibility of not

always being a good fit for the allocation. This was accomplished by allowing the cluster to be

defined as multiples of the hardware's natural allocation size. Finally, in NTFS all file names

are Unicode based, and 8.3 file names are kept along with long file names.