HIMANSHU wrote:
> I changed sector size from 512 to 8192 on target(XYZ) side but when I
> connected this device from Open-iSCSI version 868,it gave the
> following error.
> 
> Feb 24 15:36:03 localhost kernel: scsi17 : iSCSI Initiator over TCP/IP
> Feb 24 15:36:04 localhost kernel:   Vendor:XYZ    Model: iSCSI
> Volume      Rev: 0.1
> Feb 24 15:36:04 localhost kernel:   Type:   Direct-
> Access                      ANSI SCSI revision: 04
> Feb 24 15:36:04 localhost kernel: sdb : unsupported sector size 8192.
> Feb 24 15:36:04 localhost kernel: SCSI device sdb: 0 512-byte hdwr
> sectors (0 MB)
> Feb 24 15:36:04 localhost kernel: sdb: test WP failed, assume Write
> Enabled
> Feb 24 15:36:04 localhost kernel: sdb: asking for cache data failed
> Feb 24 15:36:04 localhost kernel: sdb: assuming drive cache: write
> through
> 
> How open-iscsi will handle different block size than >4k?  Is there
> any setting on initiator side or it should automatically detect
> different block size >4k.
> 
> Please help me.
> 

You are confusing two different things

block size - Is the basic allocation unit in a filesystem, and is set when first
mkfs of the filesystem for these filesystems that support it.

sector size - Is a disk's addressing unit. So when an initiator asks to
write byte 30017 on disk he is asking to write 30017/sector_size sector
at 30017%sector_size offset. In other words, disk addresses are in sectors
and not in bytes. Any sector size other then 512 is not supported in kernel.
This is nothing to do with iSCSI which is just a SCSI transport, this is to
do with the Kernel block layer itself.
(OK there is some support for sector_size != 512 but is very limited in scope)

Boaz

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