On 14 Jan 2009 at 4:25, HIMANSHU wrote: > > IET target is connected by MS initiator.Data transfer is going on on > the connected disk on initiator. > > TCP connection failed(because of any reason,service failure,problems > in kernel modules) at say 't1' second.Initiator kept trying for > reconnect. > > Initiator actually recognizes that target is down at say 't2' seconds. > > Then for the time between 't1' and 't2',data is written on the cache > on initiator side giving illusion of data transfer.After some time,it > gave delayed write error.
It's not an illusion of data transfer, but a shift in responsibility: Having buffered the data to write, the kernel is responsible to finally write the data. In HP-UX (without iSCSI) messages may look like these: vmunix: LVM: WARNING: VG 64 0x1f0000: LV 1: Some I/O requests to this LV are waiting indefinitely for an unavailable PV. These requests will be queued until the PV becomes available (or a timeout is specified for the LV). [...] vmunix: LVM: NOTICE: VG 64 0x1f0000: LV 1: All I/O requests to this LV that were waiting indefinitely for an unavailable PV have now completed. Naturally if the user panics in between, data is lost. The sysadmin has the responsibility to restore the network connection in the iSCSI case. If you application relies that the data is written upon return of a write(), it should use the O_SYNC (in Linux) open() flag. > > So data is not actually stored on the target. > > What can we do here?Using high capacity network can be the solution in > case of dedicated framework so that initiator will recognize the > failure as early as possible. I'd consider this type of failure the same as if you unplug the IDE or SCSI cable while the system is running. If your system is very stable, it can recover from the situation if the cable is reconnected. However it's usually best to avoid such situations. Just my opinion.... Regards, Ulrich --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "open-iscsi" group. To post to this group, send email to firstname.lastname@example.org 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 -~----------~----~----~----~------~----~------~--~---