6.6 Write Cache. Fujitsu MPE3XXXAT

Add to My manuals
191 Pages

advertisement

6.6 Write Cache. Fujitsu MPE3XXXAT | Manualzz

6.6

Write Cache

The write cache function of the drive makes a high speed processing in the case that data to be written by a write command is logically sequent the data of previous command and random write operation is performed.

When the drive receives a write command, the drive starts transferring data of sectors requested by the host system and writing on the disk medium. After transferring data of sectors requested by the host system, the drive generates the interrupt of command complete.

Also, the drive sets the normal end status in the Status register. The drive continues writing data on the disk medium. When all data requested by the host are written on the disk medium, actual write operation is completed.

The drive receives the next command continuously. If the received command is a "sequential write" (data to be written by a command is logically sequent to data of previous command), the drive starts data transfer and receives data of sectors requested by the host system. At this time, if the write operation of the previous command is still been executed, the drive continuously executes the write operation of the next command from the sector next to the last sector of the previous write operation. Thus, the latency time for detecting a target sector of the next command is eliminated. This shortens the access time. The drive generates an interrupt of command complete after completion of data transfer requested by the host system as same as at previous command. When the write operation of the previous command had been completed, the latency time occurs to search the target sector.

If the received command is not a "sequential write", the drive receives data of sectors requested by the host system as same as "sequential write". The drive generates the interrupt of command complete after completion of data transfer requested by the host system.

Received data is processed after completion of the write operation to the disk medium of the previous command.

Even if a hard reset or soft reset is received or the write cache function is disabled by the SET

FEATURES command during unwritten data is kept, the instruction is not executed until remaining unwritten data is written onto the disk medium.

The drive uses a write data as a read cache data. When a read command is issued to the same address after the write command, the read operation to the disk medium is not performed.

When an error occurs during the write operation, the drive makes retry as much as possible. If the error cannot be recovered by retry, the drive stops the write operation to the erred sector, and continues the write operation from the next sector if the write data is remained. (If the drive stacks a write command, for that the drive posts the command completion, next to the command that write operation is stopped by error occurrence.) After an error occurs at above write operation, the drive posts the error status to the host system at next command. (The drive does not execute this command, sets the error status that occurred at the write operation, and generates the interrupt for abnormal end. However, when the drive receives a write command after the completion of error processing, the drive posts the error after writing the write data of the write command.)

6 - 20 C141-E077-01EN

At the time that the drive has stopped the command execution after the error recovery has failed, the write cache function is disabled automatically. The releasing the disable state can be done by the SET FEATURES command. When the power of the drive is turned on after the power is turned off once, the status of the write cache function returns to the default state.

The default state is “write cache enable”, and can be disable by the SET FEATURES command.

The write cache function is operated with the following command.

WRITE SECTOR(S)

WRITE MULTIPLE

WRITE DMA

IMPORTANT

When the write cache function is enabled, the transferred data from the host by the WRITE SECTOR(S) is not completely written on the disk medium at the time that the interrupt of command complete is generated. When the unrecoverable error occurs during the write operation, the command execution is stopped. Then, when the drive receives the next command, it generates an interrupt of abnormal end. However an interrupt of abnormal end is not generated when a write automatic assignment succeeds. However, since the host may issue several write commands before the drive generates an interrupt of abnormal end, the host cannot recognize that the occurred error is for which command generally. Therefore, it is very hard to retry the unrecoverable write error for the host in the write cache operation generally. So, take care to use the write cache function.

C141-E077-01EN 6 - 21

Comments concerning this manual can be directed to one of the following addresses:

FUJITSU LIMITED

Business Planning

Solid Square East Tower

580 Horikawa-cho,Saiwai-ku, Kawasaki,

210-0913, Japan

TEL:

FAX:

81-44-540-4056

81-44-540-4123

FUJITSU COMPUTER PRODUCTS OF AMERICA, INC.

2904 Orchard Parkway, San Jose,

California 95134-2009, U.S.A.

TEL: 1-408-432-6333

FAX: 1-408-432-3908

FUJITSU CANADA INC.

2800 Matheson Blvd. East, Mississauga, Toronto,

Ontario L4W 4X5, CANADA

TEL:

FAX:

1-905-602-5454

1-905-602-5457

FUJITSU EUROPE LIMITED

2, Longwalk Road, Stockley Park, Uxbridge,

Middlesex UB11 1AB, ENGLAND

TEL:

FAX:

44-81-573-4444

44-81-573-2643

FUJITSU DEUTSCHLAND GmbH

Frankfurter Ring 211, 80807 München, GERMANY

TEL:

FAX:

49-89-323780

49-89-32378100

FUJITSU NORDIC AB

Kung Hans Väg 12, S-192 68 Sollentura, SWEDEN

TEL:

FAX:

46-8-626-4500

46-8-626-4588

FUJITSU ITALIA S.p.A.

Via Nazario Sauro, 38 20099 Sesto S. Giovanni (MI), ITALY

TEL:

FAX:

39-2-26294-1

39-2-26294-201

FUJITSU FRANCE S.A.

I, Place des Etas-Unis, SILIC 310,

94588 Rungis Cedex, FRANCE

TEL: 33-1-41-80-38-80

FAX: 33-1-41-80-38-66

FUJITSU ICL ESPAÑA S.A.

Almagro 40, 28010 Madrid, SPAIN

TEL:

FAX:

34-91-681-8100

34-91-681-8125

FUJITSU AUSTRALIA LIMITED

2 Julius Avenue (Cnr Delhi Road) North Ryde N.S.W. 2113,

AUSTRALIA

TEL:

FAX:

61-2-9776-4555

61-2-9776-4556

FUJITSU HONG KONG LTD.

10/F., Lincoln House, 979 King's Road, Taikoo Place, Island East,

Hong Kong

TEL: 852-2827-5780

FAX: 852-2827-4724

FUJITSU KOREA LTD.

Coryo Finance Center Bldg, 23-6, YoulDo-Dong,

Young DungPo-Gu, Seoul, Republic of KOREA

TEL:

FAX:

82-2-3787-6000

82-2-3787-6070

FUJITSU COMPUTERS (SINGAPORE) PTE. LTD

20 Science Park Road #03-01,

TELETECH PARK SINGAPORE SCIENCE PARK II,

Singapore 117674

TEL:

FAX:

65-777-6577

65-771-5499

FUJITSU TAIWAN LTD.

8F, Hun Tai Center, 168-170, Tun Hwa North Road,

1st Sec., Taipei, TAIWAN

TEL:

FAX:

886-2-545-7700

886-2-717-4644

FUJITSU SYSTEMS BUSINESS (MALAYSIA) SDN. BHD.

Fujitsu Plaza, 1A, Jalan Tandang 204, P.O. Box 636 Pejabat Pos

Jalan Sultan

46770 Petaling Jaya, Selangor Darul Ehsan, Malaysia

TEL:

FAX:

60-3-793-3888

60-3-793-0888

FUJITSU SYSTEMS BUSINESS (THAILAND) LTD.

12th F1., Olympia Thai Tower, 444 Rachadapisek Road,

Samsennok, Huay Kwang, Bangkok 10320, Thailand

TEL: 66-2-512-6066

FAX: 66-2-512-6068

11

Reader Comment Form

We would appreciate your comments and suggestions for improving this publication.

Publication No.

Rev. Letter Title

FUJITSU LIMITED

Current Date

How did you use this publication?

Learning

Reference

Installing

Maintaining

Sales

Operating

Is the material presented effectively?

Fully covered

What is your overall rating of this publication?

Very Good

Good

Fair

Poor

Very Poor

What is your occupation?

Your other comments may be entered here. Please be specific and give page, paragraph and line number references where applicable.

Well

Illustrated

Well

Organized

Clean

Your Name & Return Address

Thank you for your interest. Please send this sheet to one of the addresses in a left page.

advertisement

Related manuals

advertisement

Table of contents