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invalid block size

Occasional Advisor

invalid block size


Has any of you encountered this error while backing up to an MSL6060:

"Tha xMA has detected an error while writing to the device..."

"...the most probable cause is the invalid block size used to configure the backup device."

is there a way to adjust the drives block size? i'm using NSR.

Amol Garge
Trusted Contributor

Re: invalid block size


I got this from a guide:

At the end of March 2005, Microsoft released Service Pack 1 (SP1) for the Windows Server 2003
platform. With SP1, Microsoft changed the driver tape.sys to allow for NTBackup tapes written on 64-bit
Windows 2003 Server to be read or cataloged on 32-bit Windows 2003 Server systems. The change in
the tape.sys driver imposes a limit on the data transfers to a block size of no greater than 64KB.
Performance issues will be more apparent on all high-performance tape drives such as the HP Ultrium 960
and SDLT 600 using the tape.sys driver.
As a result, backup applications using HP tape drivers (hplto.sys, hpdat.sys, hpdltw32.sys,
hpdltx64.sys, and hpdltw64.sys) and tape.sys driver may experience poor performance and/or
failed backup jobs. If experiencing either of these symptoms, check the backup application with the
software vendor to see if the backup application is using the Microsoft tape driver, tape.sys.
Microsoft released a hotfix that replaces the affected tape.sys file with a version that removes the 64KB
limitation on block sizes; see http://support.microsoft.com/kb/907418/en-us.
This hotfix was integrated
into Windows 2003 Service Pack 2 (SP2).
Amol Garge
Trusted Contributor

Re: invalid block size

One more possibility:

A potential tape I/O performance issue has been discovered with Windows Server 2003 32-bit systems
configured with Emulex SCSIPort mini-port HBA drivers. This issue only affects those backup applications
using tape block sizes/transfer lengths exceeding 128KB.
Emulex SCSIPort mini-port HBA drivers use a MaximumSGList entry in the Windows registry that defines the maximum data transfer length supported by
the adapter for SCSI commands. Early Emulex drivers, version and older, set this registry entry to
a value of 33 decimal (21 hexadecimal) limiting SCSI transfers to a maximum of 128KB. Beginning with
version, this registry entry was increased to 129 decimal (81 hexadecimal) increasing SCSI
transfers to 512KB. The issue surfaces when upgrading an installed Emulex HBA SCSIPort mini-port driver
from driver version and earlier to driver version or later (driver version is
Enterprise Backup Solution design guide 121
exempt from this issue). During the upgrade, the existing MaximumSGList registry entry is not modified
from 33 to 129. Since it remains at the lower value (33), the SCSI transfer length remains at 128K, thus
possibly affecting performance when large block sizes/transfer lengths are used.

To resolve this issue, modify the MaximumSGList in the registry as follows:

CAUTION: Using the Registry Editor incorrectly can cause serious, system-wide problems. Microsoft
cannot guarantee that any problems resulting from the use of Registry Editor can be solved. Use this tool at
your own risk. Back up the registry before editing.

1. Click Start > Run to open the Run dialog box.
2. Enter regedit to launch the registry editor.
3. Navigate to the following registry key:
4. Change the REG_DWORD value from 33 to 129.

Hope this helps!