High Availability by Walter McCullough

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Papers & Training

Preliminary (off) white paper

on high availability disk

products for the HP3000

» Return to original page

by Walter McCullough

Version Date May 20, 1997

This (short) paper addresses the current need

to describe to customers and field personnel the

features and performance of 3 disk products. The paper will try to set

customer expectations so that

these products can be successfully integrated as high availability or data center

management

solutions. Data is being collected for a more detailed paper that will be released in the near future.

High Availability Storage System (Jamaica Enclosure)

The Jamaica enclosure is just that, a low cost cabinet that can hold 4 full height or 8 half height disk

drives that is supported on MPE/iX release 5.0. The drives

come in 2Gb, 4Gb, and 9Gb capacities.

The enclosure has a hot swap capability, but is only supported with the FastWide configuration.

(Hot

Swapping on SingleEnded devices may/will cause aberrant signals on the SCSI bus that could

cause

disk corruption and/or the destruction of the interface card.)

The enclosure does not support a RAID configuration but is ideal for implementing Mirrored Disk/iX,

software mirroring solution. To take advantage of the high

availability configuration, the mirrored

partners should be configured to ensure pathway redundancy. Disk failures are

recognized by the

Mirrored Disk/iX software and messages are then sent to the system console.

A UPS is required due to a new disk technology called "Write on Arrival". The UPS will guarantee

write atomicity in case of power failure, ensuring that the

MPE/iX Transaction Manager will

successfully recover pertinent data.

For more information on this topic please refer to

the ESP

document with keyword "DISK POWERFAIL".

Model 10 & 20 Disk Array (Nike)

The Nike Array is another high availability

disk solution costing more than the Jamaica enclosure but

with

greater functionality. It is supported on MPE/iX release 5.5

with a FastWide SCSI adapter

firmware release level of 3636 or greater and PowerPatch 1. The cabinet comes in multiple models

with the largest supported model containing twenty 4Gb disk

drives.

The Nike cabinet supports several RAID protocols and can be used to protect the LDEV 1. RAID-

1 is

the only protection mode supported for LDEV 1, which is hardware

mirroring. The cabinet supports a

dual SCSI connector that can be used for redundancy, but is currently not supported under

MPE/iX.

Automatic failover (or Auto-Trespass) to the other

connector is currently under development with

release scheduled for 1998. The automatic failover will give the Nike

pathway redundancy, increasing

its high availability feature set by reducing the likelihood that any of the five points of

failure will deny

access to user data.

The RAID configurations perform slightly

slower than generic disk drives or JBOD (Just a Bunch Of

Disks) due to the added complexity of the protection

algorithms, all done by the Nike processor.

These other protection algorithms may need to "look" at the data before it

goes to disk to create parity

or "repair" bits that are stored across or on other disk drives within the cabinet.

Page

High Availability disk products for the HP e3000

7/18/2008

http://www.hp.com/cgi

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Summary of content (4 pages)

PAGE 1
High Availability disk products for the HP e3000 Page 1 of 4 Jazz home > Papers & Training Preliminary (off) white paper on high availability disk products for the HP3000 » Return to original page by Walter McCullough Version Date May 20, 1997 This (short) paper addresses the current need to describe to customers and field personnel the features and performance of 3 disk products.
PAGE 2
High Availability disk products for the HP e3000 Page 2 of 4 The Nike Array also supports up to 64Kb of cache used to manage data internally. Use of this cache has not shown any performance improvement for MPE/iX. This device is configured through a separate terminal connected to a serial port on the back panel of the Nike cabinet. The interface allows the user to define the level of (RAID) protection for each disk drive within the cabinet. The cabinet also supports Hot Standby drives.
PAGE 3
High Availability disk products for the HP e3000 Page 3 of 4 installed at a remote data center. This feature allows the customer to design a disaster tolerant solution. Another feature not yet certified is SMMF (Symmetrix Multiple Mirror Facility). SMMF provides mirroring of data within the same cabinet but to drives connected to other machines. This is much like the SRDF feature but internal to the cabinet. The configuration of the EMC Symmetrix 3000 requires a trained EMC technician.
PAGE 4
High Availability disk products for the HP e3000 Page 4 of 4 but if there is only one pathway to the data then it will queue I/O requests for the drive mechanism and wait for each I/O completion until proceeding. The next problem with this configuration is a major reduction in throughput caused by MPE/iX's use of the Transaction Manager. This mechanism keeps track of changes to MPE/iX internal data structures and user data bases, such as KSAM and Image/SQL files.