HIMANSHU wrote:
> On Feb 24, 4:23 pm, Boaz Harrosh <bharr...@panasas.com> wrote:
>> 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
> Hi Boaz,
> 
> Thanks for your reply.
> 
> You are right about block size & sector. But I have some doubt. On
> target I
> am exposing the LUN with block size of 8192. Then on initiator size
> what
> could be the sector size? I am getting 8192 as sector size (As you can
> see
> in the following (main) message).
> 
> I tried exposing the LUN with 4096 as block size. On initiator (after
> connection) I am getting the following message.
> 
> Feb 23 15:12:08 localhost kernel: scsi7 : iSCSI Initiator over TCP/IP
> Feb 23 15:12:08 localhost kernel:   Vendor: XYZ    Model: iSCSI Volume
> Rev: 0.1
> Feb 23 15:12:08 localhost kernel:   Type:   Direct-Access
> ANSI SCSI revision: 04
> 
> Feb 23 15:12:08 localhost kernel: SCSI device sdb: 498688 4096-byte
> hdwr
> sectors (2043 MB)
> 
> Feb 23 15:12:08 localhost kernel: sdb: test WP failed, assume Write
> Enabled
> Feb 23 15:12:08 localhost kernel: sdb: asking for cache data failed
> Feb 23 15:12:08 localhost kernel: sdb: assuming drive cache: write
> through
> Feb 23 15:12:08 localhost kernel: SCSI device sdb: 498688 4096-byte
> hdwr
> sectors (2043 MB)
> Feb 23 15:12:08 localhost kernel: sdb: test WP failed, assume Write
> Enabled
> Feb 23 15:12:08 localhost kernel: sdb: asking for cache data failed
> Feb 23 15:12:08 localhost kernel: sdb: assuming drive cache: write
> through
> Feb 23 15:12:08 localhost kernel:  sdb: sdb1
> 
> 
>>From above message you can see that, I can able to access the device
> with
> sector size as 4096.
> 
> So my question is that why I am not able to access the LUN having
> sector
> size of 8192.
> 
> Please help me.
> 
> Thanks
> 

I'm afraid you will have to inspect the source code to know the exact details
(Search for the: "unsupported sector size" message as a start)

But even with 4k or 1k sector sizes you will see that not everything works
as expected, it is something that very few people tried and that is unsupported
in many areas of the Kernel. So you're on your own here.

You have the code and the scratch maybe you can fix things. BTW why do you need
sector_size != 512?

(Please don't top post)
Boaz





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