Factors affecting direct attached storage device performance in the application layer

3
Table 1: Characteristics of HP HDDs and SSDs enterprise-class drives
Enterprise Drives
(HDD)
Midline Drives
(HDD)
Enterprise
Value/Boot
(SSD)
Enterprise
Mainstream
(SSD)
Enterprise
Performance
(SSD)
Interface type
SAS
SATA or SAS
SATA
SATA or SAS
SAS
Interconnect
bandwidth
6 Gb/s
3 Gb/s or
6 Gb/s
3 Gb/s
3 Gb/s or
6 Gb/s
6 Gb/s
General
description
SFF and LFF Hot
Plug
SFF and LFF
Hot Plug
SFF and LFF
Hot Plug
SFF and LFF
Hot Plug
SFF Hot Plug
Capacity range
(GB)
300 – 900
500 – 3000
60 – 480
100 – 800
200 – 400
Drive Type
10K and 15K
rpm rotating
media
7.2K rpm
rotating media
NAND Flash
MLC
NAND Flash
SLC and MLC
NAND Flash
SLC
Warranty
3 year
1 year
3 year
3 year
3 year
Data retention
without power
Infinite
Infinite
3 months
minimum
< 3 months
< 3 months
Usage
environment
Mission critical -
24x7x365 up
to100% write
applications
Non-mission
critical - Low
read/write
applications
Value
Endurance -
High read/low
write
applications
Mainstream
Endurance -
Mixed
read/write
applications
High
Endurance -
Unrestricted
read/write
applications
Small form factor and large form factor drives
New HP SmartDrive hot plug drives are available in SFF (2.5-inch) and LFF (3.5-inch) HDDs and SSDs on
HP ProLiant Gen8 servers. These new SmartDrives provide the following improvements:
 Enhanced display
 Drive activity spinner
 Do Not Remove indicator
 Drive status indicator
 Smart carrier authentication
 Drive error log NVRAM
For example, if someone removes the wrong drive in a RAID array set while the drives are in rebuild mode,
that manual error will cause data loss. As a precaution against such an error, we added the Do Not
Remove LED indicator. It lights up only when the RAID array is no longer providing redundancy.
Hard disk drive I/O performance
Two factors primarily characterize drive performance: sequential data transfer rate of the media and
random I/O operations per second. Sequential data transfer rate is typically specified when reading or
writing relatively large blocks (≥64 kilobytes) of data to sequential disk sectors on the outer most tracks of
the disk, called the outer diameter (OD). This maximum sequential data rate is valid only for the OD tracks
on the drive. The rate can be 40 to 50 percent lower on the inner diameter (ID) tracks because they have a
smaller diameter with fewer sectors per track. Random I/O operations occur when reading or writing
relatively small blocks (≤8 kilobytes) of data to sectors that are scattered across the whole capacity of the
disk. The speed of the actuator seeks and the disk rotation speed determine random performance.