Chapter 11: Drives Flashcards
Write through writes information to the disk before what?
The OS is notified that the write was successful
SAS uses what legacy storage protocol?
SCSI
In NAS technology, what keeps track of where files are located?
The NAS device’s operating system
In the Fibre Channel model what is layer 0?
Physical
The sixth step in a disk array controller operation is?
Head reads servo track and waits for data to rotate underneath the head.
Servo track allows accurate tracking
For a 15,000rpm drive, how long is the rotational latency?
2ms
Linear movement of the head is called?
Seek
The third step in a disk array controller operation is?
Disk array controller executes I/O commands
Platter assembly mounted on a _______ that revolves around an axis
spindle
iSCSI allows SCSI access over what?
TCP/IP
SCSI is limited to how many drives?
14
What feature found in SCSI improves data integrity?
Cyclic redundancy checking
Seek time is the time to get what?
A Track
As a rule of thumb, doubling the number of drives will increase your throughput by how much?
50%
The platters in hard disk drives are coated with what?
Magnetic Material
The second step in a disk array controller operation is?
OS generates an interrupt
The tenth step in a disk array controller operation is?
Controller communicates a completion to the device driver
In NAS technology, what issues disk I/O requests?
The NAS device’s operating system
The time required for the disk to transfer requested data is called what?
Transfer Rate
SAS usually has how many lanes?
4
EIDE cables are typically what length?
18 inches
On a consumer grade disk, the seek operation usually takes how long?
7-10ms
LBA stands for what?
Logical Block Address
iSCSI uses what medium?
Gigabit Ethernet
PATA operates at what voltage?
5v
The ninth step in a disk array controller operation is?
PCI data is transferred into the server main memory
If data is stored on 10% of the disk surface then the disk has how much stroke?
10%
The first step in a disk array controller operation is?
Logical Block Address (LBA) is given for a read command by the OS
Drive failure puts system in what state?
Critical
In the Fibre Channel model what is layer 2?
Signaling and Framing
What are the two disk cache modes?
Write through and Write Back
The eighth step in a disk array controller operation is?
Controller initiates a DMA operation
The maximum distance of a fibre channel link is?
10Km
In terms of Hard Disk Drives, Latency is what?
The time for data to move under the head
In NAS technology, all I/O operations use what?
File-level protocols
How do RAID controller hold data in cache in the case of a power failure for years?
A battery
In the Fibre Channel model what is layer 4?
Mapping
Disk Fragmentation occurs when files are not?
Contiguous
SATA operates at what voltage?
250mv
In the context of SATA 3, what is the purpose of the Backplane?
Interconnects of hot-swap racks
On a high end disk, the seek operation usually takes how long?
3-5ms
The fundamental disk subsystem has two components
The Hard Disk & The Controller
The Active Data set size is measured by what?
Disk Stroke
The seventh step in a disk array controller operation is?
Read data is transferred to a buffer from the read head
The two types of disk connectivity are?
Parallel & Serial
The TRIM function is triggered when?
Emptying the Recycle Bin or Formatting the Drive
For a 10,000rpm drive, how long is the rotational latency?
3ms
Both EIDE and SCSI use what type of connectivity?
Parallel
SAS supports up to what speed per lane?
3Gbps each way
SATA 3 provides speed up to?
600Mbps
For a 7,200rpm drive, how long is the rotational latency?
4ms
The fourth step in a disk array controller operation is?
Command sent to target drive
what is layer 1?
In the Fibre Channel model
The most important advantage of SAS is?
Allows simultaneous processing of multiple I/O requests
What three devices does a NAS consist of?
A server, Operating System, and Storage
The fifth step in a disk array controller operation is?
Target drive processes command by moving head to the track where the data resides
In the Fibre Channel model what is layer 3?
Common Services
At a minimum there needs to be two wires for serial, what are they for?
One for sending and one for receiving
The main problem with increasing Parallel bus speed is?
Increase in electromagnetic radiation or noise
The OS “sees” SATA devices the same as?
PATA Remove Storage
In the Fibre Channel model what is layer 1?
Transmission
Storage Area Networks use what type of connections across the network?
Any-to-any
The maximum data payload for a Fibre Channel frame is?
2112 bytes
According to IBM, Fibre Channel has a max data rate of what?
4 GB/s
According to IBM, the Fibre Channel link to the server can be either one of three speeds?
1Gbps, 2Gbps, or 3Gbps
