Dell Precision 7680 Pengaturan dan Spesifikasi - Halaman 19
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pronounced for write operations, and it can be problematic for applications that are latency sensitive. One such example of this
is any application that performs thousands of random writes per second in small block sizes.
RAID 1 (Mirrored, Data Protection) volumes benefit from higher performance when drives are matched because the data
is mirrored across multiple drives: all I/O operations must be performed identically to both drives, thus variations in drive
performance when the models are different, results in the I/O operations completing only as fast as the slowest drive. While
this does not suffer the variable latency issue in small random I/O operations as with RAID 0 across heterogeneous drives, the
impact is nonetheless large because the higher performing drive becomes limited in all I/O types. One of the worst examples of
constrained performance here is when using unbuffered I/O. To ensure that writes are fully committed to non-volatile regions of
the RAID volume, unbuffered I/O bypasses cache (for example by using the Force Unit Access bit in the NVMe protocol) and
the I/O operation will not complete until all the drives in the RAID volume have completed the request to commit the data. This
kind of I/O operation completely negates any advantage of a higher performing drive in the volume.
RAID 5 as the most common and best "all-round" RAID level, RAID 5 stripes data blocks across all drives in an array (at least 3
to a maximum of 32), and also distributes parity data across all drives. In the event of a single drive failure, the system reads
the parity data from the working drives to rebuild the data blocks that were lost. RAID 5 read performance is comparable to
that of RAID 0, but there is a penalty for writes since the system must write both the data block and the parity data before the
operation is complete. The RAID parity requires one drive capacity per RAID set, so usable capacity will always be one drive less
than the total number of drives in the configuration. Not suited for applications requiring many small random data writes due to
poor random data write performance.
Care must be taken to match not only the drive vendor, capacity, and class, but also the specific model. Drives from the same
vendor, with the same capacity, and even within the same class, can have different performance characteristics for certain
types of I/O operations. Thus, matching by model ensures that the RAID volumes are consisted of a homogeneous array of
drives that deliver all the benefits of a RAID volume without incurring the additional penalties when one or more drives in the
volume are lower performing.
Precision 7680 supports RAID with more than one solid state drive configuration.
Media-card reader
The following table lists the media cards supported by your Precision 7680.
Table 14. Media-card reader specifications
Description
Media-card type
Media-cards supported
NOTE:
The maximum capacity supported by the media-card reader varies depending on the standard of the media card
installed in your computer.
Keyboard
The following table lists the keyboard specifications of your Precision 7680.
Table 15. Keyboard specifications
Description
Keyboard type
Keyboard layout
Number of keys
Values
SD card
● Secure Digital (SD)
● Secure Digital High Capacity (SDHC)
● Secure Digital Extended Capacity (SDXC)
Values
Backlit keyboard
QWERTY
● United States and Canada: 99 keys
● United Kingdom: 103 keys
● Japan: 106 keys
Specifications of Precision 7680
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