Hardware Reference
In-Depth Information
Partition Alignment
Another issue with SSDs is that they are normally designed to read and write 4K pages
and to erase data in 512K blocks. Windows XP and earlier OSs normally start partitions
63sectors into adisk,which means that the OSfile system components andclusters over-
lappagesandblocks,resultinginmorepagesbeingreadorwritten,andmoreblocksbeing
erased than necessary, which can cause a noticeable performance hit.
SSDs perform at their best when the OS's partitions are created with the SSD's alignment
needs in mind. All the partition-creating tools in Windows 7/Vista place newly created
partitionswiththeappropriatealignment,withthefirstpartitionstartinganeven2048sec-
tors into the disk. Because this is evenly divisible by both 4K (8 sectors) and 512K (1024
sectors), there is no overlap between OS file system cluster and SSD page/block opera-
tions.
Even if you are using Windows 7/Vista or another OS that normally creates aligned par-
titions, you may still have misaligned partitions if the OS was installed into an existing
partition or as an upgrade. Many of the drive manufacturers have free partition align-
ment tools available that can check and even correct the alignment ofpartitions onthe fly.
When creating new partitions on an SSD, you can optionally use the
DISKPART
command
to manually set the offset to the start of the first partition such that all partitions on the
drive will be properly aligned. With manual intervention, you can ensure that even Win-
dowsXPandearlierwillcreatepartitionsthatareproperlyalignedformaximumperform-
ance.
SSD Applications
SSDs are ideal for laptops because they are more rugged (no moving parts), weigh
less, and consume less power. The weight savings is fairly minor because the difference
between an SSD and a conventional drive of the same (or even greater) capacity is gener-
ally only a few grams. The power savings is more real—SSDs only draw about a tenth of
a watt compared to about 1 watt for an HDD (average). But even that may be overstated.
Although drawing one-tenth the power sounds like a considerable savings, compared to
other components such as the CPU, GPU, and display, each of which draw 30 watts or
more, the overall power savings in going from a standard HDD to an SSD is relatively
low in comparison to the total power consumed.
SSDs are ideal as the boot drive for desktop systems because of their performance. Using
an SSD can drop boot or resume from hibernation times dramatically. SSDs are less ideal
forstoringlargeamountsofdatabecausecapacitiesarelessthanwhatisavailableforcon-
ventional HDDs.
