Managing Hardware in Windows 7 (part 1) - Managing Memory & Managing Disks

1. Managing Memory

The processor can't access any data until it is placed in memory, and the amount of memory you have will directly impact the speed of your system. Generally, the more memory you have, the better your system will perform.

However, the architecture will limit the amount of memory available to your system. Figure 1 shows a screenshot of a 32-bit edition of Windows 7 installed on a 64-bit system that has 8 GB of random access memory (RAM).

Figure 1. Viewing system information including available memory

Even though Windows 7 recognizes that the system has 8 GB of RAM installed, it can use only 3.48 GB of this RAM. The rest of the RAM is wasted for two reasons:

• A 32-bit system can address only 4 GB of RAM.

• Some of this 32-bit address space is reserved for system devices.

In the system shown in Figure 5.22, it's reserving a little over 500 MB of addressable space for the system devices. The rest of the RAM is simply not being used.

1.1. Understanding Virtual Memory

Computer users have wanted more RAM virtually ever since computers were created. It doesn't matter how much they have; they want more. One solution that was implemented early in the history of computers is virtual memory.

Virtual memory is hard drive space used to mimic physical RAM when the physical RAM is running low. A processor can't access the data stored in virtual memory on the hard drive space but instead must move it to physical RAM. When the system needs to access data that is stored on the drive, other data in the physical RAM is moved onto the hard drive, and the requested data is swapped back to RAM.

Data is swapped back and forth between the hard drive and physical RAM in 64KB blocks. A 64KB block is also referred to as a page. So this entire process is often referred to as paging or swapping. The file on the disk is referred to as the paging file, and it is treated by Windows 7 as virtual memory.

1.2. Optimizing Virtual Memory

You can optimize the virtual memory by adjusting the amount of disk space used by Windows 7 for the paging file. The recommended size of the paging file is 1.5 times the physical RAM. In other words, if you have 2 GB of RAM, the recommended size for the paging file is 3 GB; if you have 6 GB of RAM, the recommended size is 9 GB; and so on.

Windows 7 manages the paging file by default, and you generally don't need to configure it. There are two reasons why you may need to modify these settings:

Minimize contention with the C: drive

The paging file is stored on the C: drive, which is typically also the boot and system partition. The operating system heavily uses the boot and system partition, so by moving the paging file to a different physical drive, you can minimize contention of regular operating system activity and paging.

Minimize space used on the C: drive

If you are running out of space on the C: drive, you can move the paging file another drive.

Figure 2 shows the Virtual Memory settings page. In the figure, the Automatically Manage Paging File Size For All Drives option is selected. This is the default selection when Windows 7 is installed.

Figure 2. Viewing Virtual Memory settings

The bottom of the screen shows information on paging file sizes, including the minimum allowed, recommended size, and currently allocated.

1.3. Diagnosing Memory Issues

Memory problems very often cause stop screens. A stop screen is sometimes referred to as a Blue Screen of Death (BSOD), but these stop errors aren't really that bad. Yes, your system is stopping because of a critical error, but it isn't usually dead. The error can be read, and you can get it operational again.

The blue screen includes a stop error with a hexadecimal code. For example, a stop error of 0×50 indicates a possible memory error. If you receive this error (or other errors indicating memory problems), you should access the recovery screen and run memory diagnostics, as shown earlier.

You may also find a system that doesn't have enough memory. A common symptom of a system that doesn't have enough memory is excessive paging. The symptom that the user will see and hear is disk thrashing. The LED on the drive is constantly blinking, and the disk can be heard working its little sectors off. With all this activity swapping data back and forth between RAM and the hard drive, the system is painfully slow.

If you experience disk thrashing, you should first check for disk fragmentation. If the system is not fragmented, the system needs more memory for the work the user is performing.

2. Managing Disks

Disk drives can often cause problems on any system, and you should be aware of some basic tools that you can use to resolve basic drive issues. By keeping the disk drives running optimally, you can often increase the reliability of the system.

The primary tools you'll use to manage disks are these:

• Check Disk

• Disk Defragmenter

• Diskpart

5.3.2.1. Identifying Bad Sectors

You can select the Check Now button on the Tools tab to launch the Check Disk program. This program can check for file errors on any drive and also check the drive for bad sectors. NTFS will usually locate and repair problems with files on its own, but it cannot identify bad sectors.

Check Disk can be launched via Windows Explorer by right-clicking any drive, selecting Properties, and selecting the Tools tab. When you click Check Now, the Check Disk dialog box will appear, as shown in Figure 3. Scan For And Attempt Recovery Of Bad Sectors is not selected by default, but when this is checked, Check Disk will test the disk sectors.

Figure 3. Checking a drive for file system errors and bad sectors

When you click Start, the system will first check to see if the drive is currently being used. The check can't be done on the system or boot partition in Windows immediately. If you try to run it on the boot or system partition, it will prompt you to schedule a disk check, and the check will be done on the next boot.

If the drive is currently being used but is not the boot or system partition, the systems will prompt you to dismount the drive. You can click Force A Dismount, and the check will then start.

When the scan completes, a dialog box appears indicating whether any problems were found. It starts as a small dialog box, but if you click the See Details link, you can view the complete results of the scan. The results will be similar to Listing 1.

Example 1. Output of Check Disk utility

Volume label is Windows7.

CHKDSK is verifying files (stage 1 of 5)...
  448 file records processed.
File verification completed.
  0 large file records processed.
  0 bad file records processed.
  0 EA records processed.
  0 reparse records processed.
CHKDSK is verifying indexes (stage 2 of 5)...
  528 index entries processed.
Index verification completed.
  0 unindexed files scanned.
  0 unindexed files recovered.
CHKDSK is verifying security descriptors (stage 3 of 5)...
  448 file SDs/SIDs processed.
Security descriptor verification completed.
  41 data files processed.
CHKDSK is verifying Usn Journal...
  15592 USN bytes processed.
Usn Journal verification completed.
CHKDSK is verifying file data (stage 4 of 5)...
  432 files processed.
File data verification completed.
CHKDSK is verifying free space (stage 5 of 5)...
  361873 free clusters processed.
Free space verification is complete.

					  

Windows has checked the file system and found no problems.

  11968511 KB total disk space.
  10457488 KB in 349 files.
       140 KB in 42 indexes.
         0 KB in bad sectors.
     63391 KB in use by the system.
     61904 KB occupied by the log file.
   1447492 KB available on disk.

      4096 bytes in each allocation unit.
   2992127 total allocation units on disk.
   361873 allocation units available on disk.

You can run the same CHKDSK command from the command prompt. This includes the command prompt accessible within Windows, the WinRE, or the WinPE. When running CHKDSK from the command prompt, you would use the following command:

CHKDSK x: /f /r

CHKDSK is the command. The x: is substituted for the drive letter that you want to check and repair, the /f switch directs it to fix or repair all errors it locates, and the /r switch directs it to check the disk sectors.

2.2. Defragmenting a Drive

Drives become fragmented when the files that are written to a system cannot be stored in a contiguous location. Imagine a 10-page report. If you printed this report as 10 separate pages, you could staple them together and it would be a contiguous report.

However, if you had 10 drawers, but you had room in each drawer for only one piece of paper, you could store the report in these 10 drawers. Now when you need to read the report, you'd first have to retrieve it from the 10 drawers. It would take extra time to retrieve the report before you could actually read it.

Similarly, when files are written to the system, there is sometimes limited space to store an entire file in a single location. Instead, pieces of the file are stored in different locations, and when it's read, the different pieces are put together. When this occurs too often, the entire drive is referred to as fragmented.

Drives that are excessively fragmented are often subject to disk thrashing. You can hear the drive constantly whirring and buzzing, but the performance seems excessively slow. If you do hear disk thrashing, you should check the drives to see if they are fragmented. If not, disk thrashing usually indicates the system doesn't have enough memory.

Defragmenting a drive is the process of rearranging the files so that more of them are stored in contiguous locations.

Figure 3 shows the Disk Defragmenter tool. You can access this by right-clicking a drive in Windows Explorer, selecting Properties, selecting the Tools tab, and then clicking Defragment Now.

Figure 3. Viewing the Disk Defragmenter tool

Notice that this screen includes a Last Run column. Not only does this verify that defragmentation was run (and when), but it also shows the current percentage of the disk that is fragmented.

Defragmentation is automatically scheduled to occur every week on drives that are connected to your computer. If you add additional drives, such as an external USB drive, these extra drives will automatically be added to the schedule. As long as the schedules are not modified, fragmentation is rarely a problem.

2.3. Running DiskPart

One of the command-line tools you may use to manage disks is DiskPart. The DiskPart command is primarily used to partition disks for advanced tasks.

Another time to use DiskPart is when the partition of a system disk can't be cleared using the normal GUI tools in the Disk Management snap-in. Disk Management can be added as a stand-alone snap-in to a Microsoft Management Console (MMC) or accessed via Computer Management.

As an example, one of the systems I upgraded had a built-in RAID-1 (mirror) that I wanted to break up. Instead of a single RAID-1 partition made up of the two drives, I wanted to use one drive for the operating system and have the second drive available for data.

Although I was able to break the mirror, Disk Management didn't allow me to repartition the second drive that I wanted to use for data. The partition was identified as an OEM partition, and Disk Management wouldn't even let me delete it.

Instead, I launched the command prompt, accessed DiskPart, and was able to delete the partition using the /override option and ultimately reformat the entire disk.

One of the important things to remember when using DiskPart is that you first must select the disk and then select the partition. You can use the LIST DISK command to identify what disks are available. After you select one using SELECT DISK # (where # is the disk number), you can then use LIST PARTITION to list the available partitions and select the partition you want to manipulate.