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Service Hints & Tips

Document ID: MCGN-3SXNRM

Servers - Tape backups of compressed files may fail

Applicable to: World-Wide

SYMPTOM:
1- Customer expects data compression during tape backups but sees very little.
2- Tape backups/restores fail to complete, or systems take excessive time to backup/restore files.

Typical Error messages may include:

- E56 errors when using Sytos Premium
- Intermittent backup and / or restores
- Reoccurrence of failures may be as long as several weeks

Note:
Exact symptoms on all operating system platforms with any of the supported backup applications is not known.

PROBLEM ISOLATION AIDS:

All of the following must be true for this tip to apply:

- The system is any IBM PC Server / Netfinity server properly configured* with any supported tape drive.
- The system is properly configured* with any of the following supported Operating Systems:

Banyan Vines, all System supported versions
Citrix, all System supported versions
Windows NT versions 3.51, and 4.0
OS/2, all System supported versions
SCO Open Server, all System supported versions
SunSoft, all System supported versions
Novell NetWare Versions 3.12, 4.0, and 4.11

- The system is properly configured with any of the following supported tape backup applications:

Cheyenne Arcserve, all System/NOS supported versions
Sytos, all System / NOS supported versions
Novaback Backup Exec, all System /NOS supported versions
Any other System / Nos supported backup application

- Use of a supported cleaning cartridge to clean the tape drive does not fix the problem.
- Compression is enabled on the tape drive via jumper or DIP Switch, or compression is enabled in the backup application.
- The data being backed up has been compressed by the Operating System / or Application.
- The correct supported media is being used in the tape drive.
- The tape drive has been cleaned on a regular basis.

* The term "properly configured" implies the following:

- Hardware is properly configured, i.e., cables, Adapter/Controller SCSI Bus settings.
- Correct drivers are used.
- Correct firmware levels are used at the SCSI Adapter/Controller, and the tape drive.

FIX:
Make sure the data being backed up is compressed only once, either within the Operating System/Application software or via the tape backup (through hardware or backup software).

WORKAROUND:
Disable compression in one of the mediums. Refer to the software application or tape backup application manuals for instructions on disabling data compression.

DETAIL:
Double compressing data by engaging compression in the operating system and in the tape backup results in problems that can be very difficult to diagnose. Most tape backup devices today incorporate some type of built-in hardware data compression. Problems occur when both the operating system AND the tape drive are compressing data.

SAS KEYWORDS:
PSY2, PSY2TAPE, D/T8650, UNCLASSIFIED, COMPRESSION, DATA, TAPE, D/T8642, D/T8641, D/T8640, D/T8639, D/T8638, BACKUP

	Search Keywords	PSY2, PSY2TAPE, D/T8650, UNCLASSIFIED, COMPRESSION, DATA, TAPE, D/T8642, D/T8641, D/T8640, D/T8639, D/T8638, BACKUP
	Hint Category	Retain
	Date Created	26-03-98
	Last Updated	04-02-99
	Revision Date	04-02-2000
	Brand	IBM PC Server
	Product Family	Netfinity 3000, Netfinity 3500, Netfinity 5000, Netfinity 5500, Netfinity 5500 M10, Netfinity 7000, Netfinity 7000 M10, PC Server 300, PC Server 310, PC Server 315, PC Server 320, PC Server 325, PC Server 330, PC Server 500, PC Server 520, PC Server 704, PC Server 720
	Machine Type	8638, 8639, 8640, 8641, 8642
	Model	Various
	TypeModel
	Retain Tip (if applicable)	H162989
	Reverse Doclinks and Admin Purposes	USA=A, EMA=A, AFE=A, Date last altered: A98/03/11, Owning B.U.: USA