Hi! It all has to do with buffering, memory management, and page size (among other things). I don't know the details, but why don't you inspect either the sources or get a book on the Linux kernel (like that of Robert Love)?
Regards, Ulrich On 24 Feb 2009 at 5:25, HIMANSHU wrote: > > 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 > > 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 > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "open-iscsi" group. To post to this group, send email to open-iscsi@googlegroups.com To unsubscribe from this group, send email to open-iscsi+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/open-iscsi -~----------~----~----~----~------~----~------~--~---
