Ugur erdugrul's Profile

<!--content cell-->

<!--editor pic and bio-->




AIXpert Blog

Ron Barker, Shawn Bodily and Bruce Spencer IBM Advanced Technical Support team with over 50 years of experience in UNIX.

<!-- daily blog entry points begin -->

Tuesday March 24, 2009

Increased Memory R

The same recovery procedures are followed if file system data is stored in a sector that goes bad. If the bad sector is on a redundant volume, NTFS replaces the cluster dynamically, using the data recovered by the volume manager. If the volume isn't redundant, the data can't be recovered and NTFS sets a bit in the volume file that indicates corruption on the volume. The NTFS Chkdsk utility checks this bit when the system is next rebooted, and if the bit is set, Chkdsk executes, fixing the file system corruption by reconstructing the NTFS metadata.

The use of Chkdsk on NTFS is vastly different from its use on the FAT file system. Before writing anything to disk, FAT sets the volume's dirty bit and then resets the bit after the modification is complete. If any I/O operation is in progress when the system crashes, the dirty bit is left set and Chkdsk runs when the system is rebooted. On NTFS, Chkdsk runs only when unexpected or unreadable file system data is found and NTFS can't recover the data from a redundant volume or from redundant file system structures on a single volume. (The system boot sector is duplicated, as are the parts of the MFT required for booting the system and running the NTFS recovery procedure. This redundancy ensures that NTFS will always be able to boot and recover itself.)

AIXV53AdminBestPractice

This issue was solved in multiple phases.

The DBA is running 10 jobs that result in queries which full scan 10 tables.
These queries request 1MB per IO. Now a stripe width of 32k breaks down the 1MB
IO into 32 equal pieces... and since there are 10 concurrent jobs that equates
to 32*10 or 320 concurrent request for IO. Finally, these 320 request, are
routed down one of the four channels so that would be 320/4 or 80 requests per
channel. Are you beginning to see the problem?

Coffee Drinks Illustrated

Fusion-io says ioDrive is not an SSD, although it's clearly going to compete
with a range of SSDs and related technologies that also are designed to surmount
speed and capacity obstacles of traditional hard disk drives.