What are the different form factor of HDD?
Ans:
Well, the HDD form factor means different sizes of disks. Most widely used form factor disk areas:
3.5 inch, Hight: 1 inch, width: 4 inch, depth: 5.75 inch
2.5 inch, Hight: ,6 inch, width: 2.75 inch, depth: 3.94 inch
What is Access Time in disk?
Access time = Seek Time + Rotational delay + transfer time
Larger the access time lower the performance of disk.
What is micro second and neno second?
Ans:
micro second (ms): millionth of second
nano second (ns): billionth of second
What is RAID ? and what is different RAID level?
Ans:
RAID stands for Redundant Array of Inexpesive Disk
There are different RAID levels, going to explain in one line for each.
- RAID 0: support high write but not support HA
- RAID 1: support HA but not high performance
- RAID 0 + 1: support both HA and High performance
- RAID 10: support both HA and High performance
- RAID 2: bit level not used in the
- RAID 3: block level parity bit used
- RAID 4: dedicated disk for parity bit
- RAID 5: distributed block level parity bit
- RAID 6: distributed block level multiple parity bit
- RAID DP ( Diagonal Parity): there are two parity bit one is straight forward parity bit and another based on diagonal parity bit. in this RAID level any 2 of the disk gets fails data still be available it means it support HA (High Availability) mode.
What is goal of RAID ?
There two main goal of RAID which are as:
- increase performance by striping (distribute data on several disk to distribute load)
- increase fault tolerance by redundancy (mirroring)
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Different form Factor of HDD
Both disk SSD and HDD designed with same size and shape. There are different form factor of HDD are as:
| Form Factor | Hight | Width | Depth |
| 3.5 inch | 1 inch | 4 inch | 5.75 inch |
| 2.5 inch | 0.6 inch | 2.75 inch | 3.94 inch |
What are the different Drive Speed of HDD?
Both disk SSD and HDD designed with same size and shape. There are different form factor of HDD are as:
- 5400 RPM
- 7200 RPM
- 10000 RPM
- 15000 RPM
What is relations between RPM, capacity, cost and Performance
Thumb rules are:
- Higher the RPM better the performance.
- Higher the RPM lower the capacity.
Key points about Capacity, cost, Performance, and Speed
- usually 10k and 15k RPM drives usually implements SCSI command set and SAS or FC interface.
- 5.4K and 7.2 K RPM drives usually implements ATA command set and have SATA interface.
- RPM and capacity are inversely proportional to each other. means if you increase one you have decrease another.
- Speed and capacity and inversely proportional to each other, meaning that if you have to increase the speed you have to decrease capacity.
- RPM and Performance are directly proportional to each other , meaning that one increase another will also increases.
