Table 4.5 Drive Characteristics - Fujitsu ETERNUS DX80 S2 Overview

Chapter 4 System Configuration
4.4 Drives
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SSDs
SSDs are reliable drives with high performance. SSDs are used to store high performance databases and
other frequently accessed data.
SSDs use flash memory as their storage media and provide better random access performance than SAS
and Nearline SAS disks. Containing no motors or other moving parts, SSDs are highly resistant to impact
and have low power consumption requirements.
SSDs support Single Level Cells (SLC) and Multi Level Cells (MLC).
- 100GB, 200GB, and 400GB SLC type SSDs are available.
- 400GB and 800GB MLC type SSDs are available. Because MLC type SSDs are cheap, cost can be reduced.
When SLC type SSDs (which can only record two states in a cell) are compared to MLC type SSDs (which can
record four states in a cell), a higher capacity can be achieved with MLC type SSDs.
Even though SSDs with flash memory have limits on the number of rewrite operations, both SLC and MLC
type SSDs, which are supported by the ETERNUS DX Disk storage system, have the high level wear leveling
function and sufficient extra areas to prevent the number of rewrite operations from exceeding the limit
within the product warranty period.
Note that the number of rewrite operations may exceed the limit within the product warranty period if
400GB MLC type SSDs are used in a RAID1 configuration that has a high I/O access load. Using a RAID1+0,
RAID5, RAID5+0, or RAID6 configuration is recommended when 400GB MLC type SSDs are used.
The table below shows the drive characteristics of SAS disks, Nearline SAS disks, and SSDs.
Table 4.5 Drive characteristics
Type
SAS disks
Nearline SAS disks
SSDs
Some functions cannot be used with some types of drives.
• Eco-mode cannot be set for SSDs.
• Do not use different types of drives in a RAID group. Use the same type of drives when adding capacity to
a RAID group (RAID Migration, Logical Device Expansion).
For details on each function, refer to
Reliability
Good
Reasonable
Very good
"Chapter 5 Basic Functions" (page
41
ETERNUS DX80 S2/DX90 S2 Disk storage system Overview
Copyright 2013 FUJITSU LIMITED
Performance Price per bit
Good Reasonable
Reasonable
Very good
48).
Low
High
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