Information Technology Reference
In-Depth Information
Swap used. This is the size of the swap file, which is the area of virtual memory that MacBook Air is actu-
ally using. So even though the entire virtual memory cache may be 25 or 30GB, the swap file is (or should be)
vastly smaller. It should actually be 0 most of the time, but it may grow to a few megabytes. If you see that it
grows to hundreds of megabytes over a short period, MacBook Air likely doesn't have enough RAM for the
programs you're running.
On any other Mac, you could solve most memory problems simply by adding more RAM to the system. Unfortu-
nately, this isn't an option with MacBook Air because the memory chips are soldered to the motherboard, which
means they can't be replaced or upgraded.
Monitoring hard drive usage
Having enough RAM is crucial for system stability, but everything in RAM was originally stored on the hard
drive. This means that it's nearly as important to monitor your hard drive activity. The crucial thing here is how
often your system asks the hard drive to read data from, and write data to, the drive:
Reading data from the hard drive. Hard drives are extremely fast and they read data from the drive all the
time. However, a hard drive is still relatively slow compared to RAM, so if the hard drive has to read data ex-
cessively, it slows down your system. Excessive drive reading is most often a sign that your hard drive is de-
fragmented.
Writing data to the hard drive. If your hard drive is writing data back to the drive excessively, it's usually
a sign that MacBook Air doesn't have enough RAM for all the programs that you're running. Try shutting down
a few.
MacBook Air files don't easily get defragmented (that is, broken into smaller chunks and spread around the hard
drive). This is probably why MacBook Air doesn't come with a disk-optimization utility to fix defragmentation.
However, defragmenting can happen, so to fix it you need a program such as iDefrag from Coriolis Systems
( www.coriolis-systems.com ). It costs $30.95, but there's a demo version that defrags up to 110MB.
If you often get the spinning wait cursor (the rainbow-colored spinning cursor that appears when the system is
taking its sweet time to complete some task), excessive drive reads and writes could be the culprit. To check,
run Activity Monitor (in Launchpad, choose Other →Activity Monitor) and then click the Disk Activity tab,
shown in Figure 11.5.
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