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The Pane Diagnostics

Evaluate RAM Size

Introduction to virtual memory

The amount of main memory (RAM, Random Access Memory) installed in a computer can be very important for the system’s achieved computing performance. If not enough memory is available, the speed of the computer will significantly decrease. However if too much memory is installed, capacities that are not really needed will be left unexploited. Unnecessary costs will be the result.

Which memory size is the optimum will depend on how you use your computer, in particular, which applications you are using, which data is processed by the applications, and to which degree programs are being used simultaneously, causing them to be held in memory at the same time. OS X keeps very detailed internal statistics how the amount of available memory is used by each of the programs. TinkerTool System can evaluate these statistics to assess whether the size of RAM installed in your computer is appropriate for your typical work. This will give you an important aid to decision-making if you should purchase more RAM for your computer, and whether additional memory will actually enhance performance.

Background Knowledge

Like in any up-to-date operating system, no running program has the permission to access main memory directly. This is left to the inner core (kernel) of the operating system only. For each running program (also known as process), the hardware simulates a separate memory space. Each process runs in its own, completely separated area which appears to be exclusively owned by it. The memory spaces of other processes are completely invisible for the process in focus. With this approach, a process is neither capable of spying out the data of others, nor can it intentionally or unintentionally overwrite data in the spaces of other processes. This is one of the most important techniques which ensure that an operating system is stable and safe. Programs are strictly shielded against each other. Even “bad” applications cannot crash other processes or the operating system.

This technique is called virtual memory. It is essentially managed by a hardware component inside the processor, called Memory Management Unit or MMU. For each access to (virtual) memory, the MMU decides which memory should be actually accessed internally: Virtual memory is either being mapped to real main memory, or to special files on the system disk, the so-called swap space. Mapping virtual memory to real memory is done in blocks, organizational units that are called pages. With OS X, each page always has a size of 4 KiB.

The system tries to map virtual memory to real main memory as long as possible. However, if too many processes are running simultaneously, or too much data is being processed at the same time, the amount of main memory available will no longer suffice at one point to host all pages of needed virtual memory. In this case, a page from main memory will be transferred to disk to make room. To do this, the system selects a memory page which is very likely not required by any process in the near future. By transferring a page of memory contents to disk, a block of memory in RAM has now become free and can be used by another process. When a page on disk is later being accessed by the process associated with it, it has to be transferred back into main memory. Another page will now be selected to be thrown out, and the two pages swap places.

Because main memory and hard drives work with very different speeds, access to paged-out memory can be 10,000 to 100,000 times slower than accessing memory in RAM. For this reason, the perceived speed of a computer can decrease drastically if too many page-outs take place, i.e. there is not enough main memory to hold as many of the used memory pages in the quickly accessible area as necessary. The theoretically best usage of memory has been reached when main memory is being used completely (almost no memory is free), and no swap space is in use. In this case, all data will be in the fast RAM and no part of the RAM is left unexploited.

In addition to swapping out memory pages to the system’s disk drive, the latest versions of OS X are capable of using another location to hold pages which no longer fit into standard memory: Because a hard drive is so significantly slower than RAM, the operating system can decide to sacrifice a small part of its RAM and use this part to store swapped-out pages after using data compression on their contents. This is called compressed memory. Instead of writing a memory page to disk, the system compresses the page and writes it to a specific RAM area reserved for that purpose. Reducing the amount of memory available to applications even further by reserving parts of it for memory compression, is a critical step of course. The system has to consider very carefully whether the gain of compressing/decompressing data in RAM instead of reading/writing to swap space outweighs the effect of losing some amount of available RAM.

Evaluating the available memory size

As already mentioned, assessing the amount of memory is only possible when relating it to the typical usage of memory during the daily work with your computer. Whether you have enough memory will depend on what applications you are using and how you are using them. For this reason, a meaningful evaluation of memory size will be possible only if the operating system had the chance to monitor typical usage of memory within a certain time interval. Perform the following steps to let TinkerTool System evaluate the memory usage statistics:

  1. Open the tab item Evaluate RAM Size in the pane Diagnostics.
  2. Press the button Refresh Values.

The current statistical readings will now appear in the upper box, the evaluation in the lower box Results. An evaluation is possible only after the system has been switched on for at least 2 hours.

The time of operation of OS X in which the statistical data could be collected is shown in the last line of the upper box. You have to decide for yourself if the computer has been used in a “typical” way in this period. In case the usage was more untypical, e.g. because you have used more applications simultaneously than normal, or because you have worked on an unusual “gigantic” document that has consumed an extraordinary amount of memory, the results will not be meaningful.

Evaluate RAM size
Evaluate RAM size

In case you decide that usage of the computer has not been typical enough to allow a meaningful assessment, perform the following steps:

  1. Restart OS X.
  2. Use your computer for at least two hours with the typical workload this computer has been purchased for.
  3. Launch TinkerTool System again, and once more navigate to the feature Evaluate RAM size.

The upper box lists selected data from the memory statistics maintained by OS X:

Apple has changed the terminology for memory statistics multiple times during the lifetime of the operating system. TinkerTool System 4 attempts to match the concepts introduced with OS X 10.10.3. The same words may relate to very different readings depending on what version of TinkerTool System and what version of OS X or Mac OS X have been used to acquire the memory values. There are currently three generations of operating systems that established different terms for memory statistics: Systems between Mac OS X 10.0 and OS X 10.8.5, systems between OS X 10.9 and OS X 10.10.2, and systems OS X 10.10.3 and later.

The box Results shows the current evaluation based on the statistics shown in the upper box. The assessment contains a textual explanation and a short overall result like “good” which is additionally represented by the image of a traffic light. The program differentiates between the following results:

Test Finder Copy

The Finder application typically used in OS X to work with files and folders is known to be affected by specific flaws which depend on the version you are using. In particular, the issues affecting file copy operations are critical, because you may lose data when you rely on the assumption that a copied file will always be absolutely identical to its original. This is especially true when you consider that the Finder also plays a role in the operation of Time Machine, the backup solution of OS X.

TinkerTool System can verify if the Finder is capable of performing the following operations correctly. They are known not to work reliably when specific versions of the Finder and specific file system types are used that are source and destination of the copy operation:

File system type means the format of a disk or disk partition, or the transfer protocol used when accessing a file server in the network, respectively. The Finder behaves differently when copying between two HFS hard drives, for example, or between an HFS disk and a memory stick formatted using the FAT standard of Windows.

Check file copy operations
Check file copy operations

You can let TinkerTool System check two given disks against your version of the Finder. TinkerTool System can control the Finder remotely to test whether the operation runs as expected or not. To perform the check, you only have to specify two folders between which test files should be copied.

To run the tests, TinkerTool System needs less than 200 kB on both disks. All files written during the check will be erased automatically after the tests have been completed.

When working with file system types, only the file system families play a role for the behavior of the Finder, not specific sub-types. Messages shown by TinkerTool System during this check refer to the family only. For example, the file systems “HFS” and “HFS+ journaled, case-sensitive, encrypted” are both represented by the family “HFS”.

Perform the following steps to test the Finder:

  1. Open the tab item Test Finder Copy on the pane Diagnostics.
  2. Drag a folder on the first disk to be checked from the Finder into the field Folder 1. You can also click the button […] to navigate to the folder, or click on the white area to enter the UNIX path of the folder.
  3. In the same fashion, specify a different folder lying on the second disk to be tested in the field Folder 2.
  4. Now press the button Run Test. After a few seconds, the outcome of the test will appear in the lower section of the pane.

The button can only be pressed if the aforementioned conditions are met for the two folders. The pane will show you in advance whether the test can be performed, or if there is a possible problem with the selection of folders.

TinkerTool System automatically tests the copy operations in both directions, i.e. copying from folder 1 to 2, and from 2 to 1. The order of the two folders doesn’t play any role for this reason. Because TinkerTool System is controlling the Finder remotely, you might hear the sound effects the Finder uses for copy operations during the test.

A test that succeeded without problems will be displayed by a check mark with green background, a test which has failed is shown by a cross marked red.

A failure of test 1 indicates that the Finder is not capable of copying Extended Attributes for files and folders if they are not stored natively, i.e. not on a disk using the format “HFS+”, or on an AppleShare file server. This failure may not be relevant to you. Emulated Extended Attributes are mainly used when you operate the system as file server, sharing files with older SMB or NFS network protocols. If you don’t use your computer in that way, it will be very likely that your installation of OS X has never created files with such attributes.

A failure of test 2 indicates that the Finder cannot copy symbolic links which have Extended Attributes attached. This failure may also not be relevant to you, but such situations are more likely than the ones of test 1. For example, you may see such objects as part of applications which have older software library frameworks embedded. These frameworks could store symbolic links which are additionally marked as legacy alias via an Extended Finder Attribute. In practice, you will notice such a problem in situations where the Finder unexpectantly cancels a running copy operation with the message that an object could not be found (error –36) although the object is there.

Please note that TinkerTool System is only testing whether the Finder is working as expected. The application cannot repair any defects it might have detected in the Finder.

If one of the tests is failing when you had selected two HFS+ disks for the copy operation, you unfortunately have to expect that Time Machine also won’t work correctly. Because the Finder is an indirect part of some copy operations performed by Time Machine, backing up or restoring data can also lead to corruption of copied files.

Inspecting Optical Disks

If your computer contains one or more optical disk drives with writing capabilities, you can use TinkerTool System to retrieve detail information about inserted disk media, like CDs, DVDs, or Blu-Ray Discs. This feature is helpful to find out the actual manufacturer of a storage medium, or to get information about the recording format of a disk. Depending on the type of medium and its storage format, the amount of data you can retrieve will be very different. With appropriate media, TinkerTool System may include the following detail information in the results:

Not only the type of storage media, but also the question if data has already been recorded on the disk will determine which information items can be retrieved and which won’t.

Inspect optical disks
Inspect optical disks

To inspect optical disk media, perform the following steps:

  1. Open the tab item Inspect Optical Disks on the pane Diagnostics.
  2. If multiple optical drives are connected with your computer, select the desired drive with the pop-up button Disk Drive.
  3. Ensure that the media to be inspected has been inserted into this optical disk drive. You can use the button with the eject symbol to eject a disk, or, in case of a drive with disk tray, use it to open and close the tray. Wait until drive and OS X have recognized the inserted disk.
  4. Press the button Inspect Disk.

The analysis will be shown in the box Results after a few seconds.

Note the difference between the items Media Type and Media Behavior: If you have recorded digital video on a disk of type DVD+R and have correctly finalized this recording session, the physical type of medium will be DVD+R, but the disk will finally behave like a DVD-ROM.

In case you are not using the typical “Superdrives” by Apple, the application will only support optical drives which can both read and write disks.

Check Time Machine

Time Machine is the name of Apple’s technology to automatically create backup copies of your computer’s hard drives. Backups are created silently in the background each hour, and outdated file sets are automatically removed, keeping hourly backups for the last day, daily backups for the last week, and monthly backups until the destination device is full. Each backup set contains a nearly complete snapshot of the contents of all disks for which Time Machine has been activated. “Nearly” means that Time Machine automatically omits files which are considered unimportant or which can be recreated, like log files, the Trash, caches, the Spotlight search index, etc. Although the entire system can be restored for each point in time for which a backup is available, Time Machine technically stores the differences between two subsequent backup operations only (incremental backup). Differences are handled at the file level, i.e. if a single byte in a file X has changed, the entire file X will be copied during the next Time Machine backup run.

Check Time Machine
Check Time Machine

Time Machine usually does not need any maintenance. You just define which disk volumes should be included, what destination drive should be used, and switch Time Machine on. However, there can be certain cases where Time Machine may not run as expected, for example if there is a file system problem on one of the source volumes, or if there was a power failure during a Time Machine run. TinkerTool System can help you to detect possible problems with backups by controlling one of the diagnostic features of Time Machine with a few simple clicks: You can select two different backup sets and compare all their files, hereby showing the “true”, incremental contents of a Time Machine backup, not the simulated view in the Finder or the Time Machine user interface, which always shows the entire effective backup set at a selected point in time. If some part of Time Machine is failing, this will mean that although specific files have been modified, they have not been included in the next incremental backup copy corresponding to the Time Machine snapshot taken immediately after the modification time. For typical Time Machine problems, the updates for an entire folder would be missing, which can be detected easily when comparing the two backups preceding and following the modification of files in that folder.

As a side effect, you can also use this feature to determine which files have changed on your computer at at a particular point in time, or to assess how many files with what storage size are typically part of your backups every hour.

In an alternative mode of operation, it is also possible to compare the current data on your computer (more exact, all files which are selected to be handled by Time Machine) with a specific backup session. This feature is helpful to detect implementation errors in Time Machine. You can immediately see whether the data that should be copied has actually been copied. Note that this type of compare operation takes a significant amount of time, because all files on your computer have to be checked.

To start the comparison of two Time Machine backups, perform the following steps:

  1. Open the tab item Check Time Machine on the pane Diagnostics.
  2. Ensure that the correct backup destination disk is shown at Time Machine Disk. This is the disk currently considered active by Time Machine. You cannot influence this automatic selection via TinkerTool System. In case Time Machine has been configured to use a network file server instead of a local disk drive (this includes the Apple Time Capsule), press the button Connect to network disk. TinkerTool System will then establish the connection to the server and scan the remote data. For a slow WLAN network, this scan may take several minutes.
  3. At Times, select the two points in time for which the backup sets should be compared. The times must be different, but their order does not play a role. To choose the “live” data on your computer for comparison, select the last item —All backup items—.
  4. If Time Machine is configured to create backup copies of multiple disk volumes, select the desired disk to compare, using the pop-up menu Volume. (This won’t be necessary if you had selected —All backup items—).
  5. Press the button Start.

Depending on the size of your backup and the amount of data differing between the two selected backup sets, the compare operation may need a few seconds or several minutes to complete. The results will be shown in the table.

If you move the mouse cursor over an entry in the column Changes, TinkerTool System will display a short textual explanation, so you don’t need to learn the abbreviations.

TinkerTool System can rescan the Time Machine disks connected to your computer when you changed the configuration or replaced the destination disk. To do so, press the button Rescan.

TinkerTool System automatically tries to determine if a backup operation is currently in progress. In this case, the warning message A backup or other Time Machine operation is currently running. is shown at the bottom of the window. Although it is usually safe to use other Time Machine features during this phase, we don’t recommend to do this, because the two simultaneously running operations could slow down each other, causing significant performance problems.

In case Time Machine is using a network volume for its backups, the connection to the remote drive will still be held open after the compare operation has completed and even when you quit TinkerTool System. This gives you the chance to quickly start a new scan operation later, but it might not be intended, for example when you have a mobile computer and like to leave the network. To avoid the permanent connection, press the button Eject network disk after you completed your work with Time Machine diagnostics.