Problems trying to use LTO block size above 64K on Windows 10

[David C Partridge]

I'm trying to use a blocksize of 256kB with an LTO-2 (Ultrium 460) drive on Windows 10 x64

The SCSI adapter MaxSGList is set to 65 which should be good for block sizes up to 512kB.

However the device is still reporting a maximum blocksize of 64kB. at least according to Starwind:

12/20 17:47:40.091 2ab8 SPTI: '\\?\scsi#sequential&ven_hp&prod_ultrium_2-scsi#6&3b67cb81&1&000300#{53f5630b-b6bf-11d0-94f2-00a0c91efb8b}': 'HP Ultrium 2-SCSI F63D': adapter 4, bus 0, target 3, LUN 0; maxTransferLength 65536, alignmentMask 0x0

The driver I'm using is hplto.sys, and the Device Manager "Tape Drive Parameters" tab for the device shows Maximum Block Size of 16MB.

So something is limiting it to 64kB :( 

Is there some Windows registry setting I need to "tweak" to raise the SPTI MaxTransferLength?

Or? ???

Thank you

Dave

[David C Partridge]

Bump ...

Someone in HP must know this stuff?  The code is using IOCTL_STORAGE_QUERY_PROPERTY with PropertyId = StorageAdapterProperty to query the MaxTransferLength of the tape drive and that's what's returning 64kB.

Thanks, Dave

[Curtis_Ballard]

LTO tape drives support a larger transfer size than just about any controller and that parameter is MIN(device support, controller support) so it ends up being driven by the controller and the controller driver, not by the tape drive.  There are some controllers that have a 64KB maximum.  The HPE P212 without expansion memory is an example of one such controller.

[David C Partridge]

Yes, that does appear to be the problem with the Adaptec driver.  Are there any brands of Ultra 320 SCSIs card that you know will support larger buffers?

Thank you, Dave

[Curtis_Ballard]

While I haven't used one with Windows 10 the Atto parallel SCSI controllers and LSI parallel SCSI controller both supported pretty good transfer sizes the last time I used them.