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CompTIA® Server+ : Difference Between Memory Types , Different Chassis Types

SATA (Serial ATA)

  • Serial ATA (SATA) transfers data in a half-duplex channel at 1.5 Gbps With SATA II, introduced in 2003, speed was increased to 3 Gbps.

  • SATA drops the master/slave shared bus of Parallel ATA, giving each device a dedicated cable and dedicated bandwidth.

  • SATA allows hot swapping, whereas Parallel ATA does not.

  • SATA cables use 7-pin, and can be up to 1 m (39 in) long, PATA ribbon cables, in comparison, carry either 40- or 80-conductor wires and are limited to .46 m (18 in) in length.

  • SATA drives may be plugged into Serial Attached SCSI (SAS) controllers and communicate on the same physical cable as native SAS disks.

  • The power connector for SATA is completely different from that of PATA. While SATA uses 15-pin connector, PATA uses 4-pin Molex connector. Note that multiple pins are used for carrying same voltage in SATA.

PATA : Parallel advanced technology attachment (originally called ATA and sometimes known as IDE or ATAPI) was the most dominant desktop computer storage interface from the late 1980s until recently, when the SATA interface took over. PATA hard drives are still being utilized today, especially in external hard drive boxes, but they're becoming rare. Some cheaper high-end server storage devices have also used PATA. Like SCSI, PATA has also gone through many revisions. The most recent version of PATA is UDMA/133 which supports a throughput of 133 MB/s.

1.2 Deploy different chassis types and the appropriate components

Cooling : The cooling methods used in PCs range from simple fan exhaust to pump out hot hair to complicated systems like Heat pipes and Peltier coolers.

  • Heat sinks: Fans may not be sufficient to cool the computer system where the computer is housed with high power processors. In such cases heat sinks are attached to the processor using conductive thermal compound to distribute the heat in the surroundings. Here, the heat is radiated using convection from hot surface to cooler surroundings.

  • Heat pipes: If the heat generated in the computer is high enough that the heat sinks are unable to cool the devices sufficiently, it may be necessary to cool the devices using fluids. Heat pipes are small tubes, built into cooling fins, that are filled with thermally conductive fluid. On heat absorption, the fluid vaporises. The vaporised fluid gets transferred to a different part of the system, and condensed.
    Peltier coolers: A Peltier device is an electronic component that gets colder whn an voltage is applied. The method is more suitable if the ambient temperatures inside the computer are high, and other methods of cooling are inefficient.

  • A shroud is a plastic or metal conduit that directs air to (or from) a CPU or any other heat producing device for cooling the device.

  • HVAC stands for Heating, Ventilation, and Air Conditioning. HAVAC is used for environmental conditioning of large computer rooms.

  • The chassis intrusion switch is used to ensure that the computer remain shut down when the case is open. Sometimes, it will also prevent booting of the computer (even after the case is closed) to warn that there was an intrusion.

  • A 19-inch rack is a standardized frame or enclosure for mounting multiple equipment modules. Each module has a front panel that is 19 inches (482.6 mm) wide, including edges or ears that protrude on each side which allow the module to be fastened to the rack frame with screws. Note that 1U equals a height of 1.75 inches.

1.3 Differentiate between memory features / types and given a scenario select appropriate memory

ECC (Error Checking and Correcting) memory means that data that is being read or transmitted will be checked for errors and, if necessary, corrected immediately. It includes a fault detection/ correction circuit that can fix memory errors at run time. To determine if a memory stick is ECC, add up the number of chips on the stick. If it is evenly divisible by 3 then it is ECC.

Some forms of ECC can only recognize single bit errors but cannot correct them, but extended ECC can both recognizes and correct single-bit errors. It requires more bits so it ios more expensive then non-ECC and slightly slower too.

Non ECC: It is found in client workstations where data integrity is not a major concern. It requires fixing memory errors to improve performance.

RAM is classified according to its buffering status

  • 1. UnBuffered: It is RAM designed for consumer purpose like in PCs. Un buffered memory communicated directly with processing chip.

  • 2. Buffered: It is designed to protect the memory from electrical load by providing a temporary data storage called buffer. It is used in systems which require larger RAM.

  • 3. Registered: It is same as buffered but is current technology. Buffering the address and control inputs reduce the load and allow connection up to 8 DIMMs to a controller.

Important Disk RAID levels:

  1. a. RAID 0: Disk Striping without parity. Minimum 2 disks are required. RAID 0 doesn't provide any fault tolerance, but read/ write to the disk will improve

  2. b. RAID 1: Disk Mirroring and Disk Duplexing. Disk Mirroring requires at least two partitions of same size. Each partition should be on a different physical drive. In other words, minimum 2 disks are required. For disk duplexing minimum 2 disks and 2 controllers are required. RAID 1 provides good fault tolerance, though disk access is slower compared to disk striping

  3. c. RAID 2: Disk Striping with Error correction.

  4. d. RAID 3: Disk striping with error correction code stored as parity

  5. This takes a striped array as in RAID 0, then adds a parity hard disk drive to the array. This parity information is vital if one drive fails. If a drive should fail in this situation, the parity drive can be used to restore blocks that have been broken due to data corruption.

  6. e. RAID 4: Disk striping with large blocks allocation.

  7. f. RAID 5: Disk Striping with Parity. Disk Striping with Parity requires at least three partitions of same size, and each partition should be on a different physical drive. In other words, minimum 3 disks are required for disk striping with parity. Fault tolerant, less expensive than disk mirroring. If more than one disk fails, data can't be recovered. You still need to depend on tape back up for multiple disk failures.

  8. RAID 5 is similar to RAID 3, except the parity information is spread across all drives, this allows all drives to be able to rebuild the array if a drive fails. In RAID 3 parity is written to only one drive.

  9. Note: compared to disk striping or disk striping with parity; Disk mirroring has more overhead, as the entire disk get copied to another disk.

  10. RAID 10 describes Mirrored Striping. It is a mode 0 array, plus a mode 1 array, striped. For example, if you have striped data into two drives, each drive is mirrored in RAID 10. That is a total of 4 drives.

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