IBM E850C, Technical Overview And Introduction

Page: 72 / 160

58
IBM Power System E850C: Technical Overview and Introduction
2.10.4 Easy Tier
The Power E850C server supports both HDDs and SSDs in the SFF bays, which are
connected to the storage backplane and accessible from the front of the server. The 1.8-inch
bays support only SSDs. It is possible to create multiple arrays using any of the storage
controller options. However, you cannot mix HDDs and SSDs in a standard (non-Easy Tier)
array. Instead, you would need to create separate arrays for HDDs and SSDs.
All of the storage controller options also support Easy Tier functionality, which allows them to
support mixed arrays of HDDs and SSDs. When the SSDs and HDDs are under the same
array, the adapter can automatically move the most accessed data to faster storage (SSDs)
and less accessed data to slower storage (HDDs).
No coding or software intervention is needed after the RAID is configured correctly. Statistics
on block accesses are gathered every minute. When the adapter detects that some portion of
the data is being frequently requested, it moves this data to faster devices. The data is moved
in chunks of 1 MB or 2 MB called
bands
.
By moving hot data onto faster SSDs, Easy Tier can dramatically improve the performance of
applications that are limited by disk I/O operations. Cold data blocks are moved onto more
cost effective HDDs, reducing the overall cost. Combining this process with the dual controller
storage backplane with write cache can provide even higher levels of overall storage
performance.
From the operating system point-of-view, there is just a regular array disk. From the SAS
controller point-of-view, there are two arrays with parts of the data being serviced by one tier
of disks and parts by another tier of disks.
Figure 2-14 shows a representation of an Easy Tier array.
Figure 2-14 An Easy Tier array