IBM DS8884 Series User Manual

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If your workload is critical, consider isolating it from other workloads. To isolate

the workloads, place the data as follows:

v On separate RAID drive groups. Data for open systems or IBM Z hosts is

automatically placed on separate arrays, which reduce the contention for drive

use.

v On separate device adapters.

v In separate processor nodes, which isolate use of memory buses,

microprocessors, and cache resources. Before you decide, verify that the isolation

of your data to a single node provides adequate data access performance for

your application.

Count key data

In count-key-data (CKD) disk data architecture, the data field stores the user data.

Because data records can be variable in length, in CKD they all have an associated

count field that indicates the user data record size. The key field enables a

hardware search on a key. The commands used in the CKD architecture for

managing the data and the storage devices are called channel command words.

Fixed block

In fixed block (FB) architecture, the data (the logical volumes) are mapped over

fixed-size blocks or sectors.

With an FB architecture, the location of any block can be calculated to retrieve that

block. This architecture uses tracks and cylinders. A physical disk contains multiple

blocks per track, and a cylinder is the group of tracks that exists under the disk

heads at one point in time without performing a seek operation.

T10 DIF support

American National Standards Institute (ANSI) T10 Data Integrity Field (DIF)

standard is supported on IBM Z for SCSI end-to-end data protection on fixed block

(FB) LUN volumes. This support applies to the IBM DS8880 unit (98x models).

IBM Z support applies to FCP channels only.

IBM Z provides added end-to-end data protection between the operating system

and the DS8880 unit. This support adds protection information consisting of CRC

(Cyclic Redundancy Checking), LBA (Logical Block Address), and host application

tags to each sector of FB data on a logical volume.

Data protection using the T10 Data Integrity Field (DIF) on FB volumes includes

the following features:

v Ability to convert logical volume formats between standard and protected

formats supported through PPRC between standard and protected volumes

v Support for earlier versions of T10-protected volumes on the DS8880 with non

T10 DIF-capable hosts

v Allows end-to-end checking at the application level of data stored on FB disks

v Additional metadata stored by the storage facility image (SFI) allows host

adapter-level end-to-end checking data to be stored on FB disks independently

of whether the host uses the DIF format.

Notes:

Chapter 2. Hardware features 51

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IBM DS8884 Series Specifications

General

Model	IBM DS8884 Series
Drive Types	SSD, HDD
Power Supply	Redundant Power Supplies
RAID Levels Supported	RAID 5, RAID 6, RAID 10
Host Interface	Fibre Channel, iSCSI, SAS
Controllers	Dual active-active
Form Factor	Rack-mountable
Operating System Support	AIX, Linux, Windows
Data Encryption	Yes
Type	Enterprise Storage System