On Oct 14 2010, 1:45 pm, "Ulrich Windl" <[email protected]
regensburg.de> wrote:
> I was investigating the status of building a RAID1 over iSCSI-connected 
> devices managed by multipathd (SLES10 SP3 Release Notes said it won't work). 
> Here are some of my findings:
>
> 1) The multipath-devices cannot be opened exclusively my mdadm:
> # mdadm --verbose --create /dev/md0 --raid-devices=2 --level=raid1 
> --bitmap=internal /dev/disk/by-id/scsi-3600508b4001085dd0001100002260000 
> /dev/disk/by-id/scsi-3600508b4001085dd0001100002290000
> mdadm: Cannot open /dev/disk/by-id/scsi-3600508b4001085dd0001100002260000: 
> Device or resource busy
> mdadm: Cannot open /dev/disk/by-id/scsi-3600508b4001085dd0001100002290000: 
> Device or resource busy
> mdadm: create aborted
>
> open("/dev/disk/by-id/scsi-3600508b4001085dd0001100002260000", 
> O_RDONLY|O_EXCL) = -1 EBUSY (Device or resource busy)
>
> 2) The device-mapper files seem to be no SCSI Devices:
> # mdadm --verbose --create /dev/md0 --raid-devices=2 --level=raid1 
> --bitmap=internal /dev/dm-18 /dev/dm-19
> mdadm: /dev/dm-18 is too small: 0K
> mdadm: create aborted
> rkdvmso1:~ # sdparm -a /dev/dm-18
> unable to access /dev/dm-18, ATA disk?
>
> 3) The iSCSI devices are SCSI-devices, but are busy:
> # sdparm -a /dev/sdax
>     /dev/sdax: HP        HSV200            5000
> Read write error recovery mode page:
>   AWRE        1  [cha: n, def:  1]
>   ARRE        1  [cha: n, def:  1]
>   TB          1  [cha: n, def:  1]
>   RC          0  [cha: n, def:  0]
> [...]
> # mdadm --verbose --create /dev/md0 --raid-devices=2 --level=raid1 
> --bitmap=internal /dev/sdax /dev/sdbo
> mdadm: Cannot open /dev/sdax: Device or resource busy
> mdadm: Cannot open /dev/sdbo: Device or resource busy
> mdadm: create aborted
>
> I'm not a specialist on mdadm, so please if I did something wrong, please 
> tell me.

Hi,

I have been looking at related but not identical question: to
replicate local disk to another server via iSCSI and md mirroring
(RAID1, no multipath). While making that setup I noticed that open-
iscsi times out SCSI commands if the network falls away long enough.
Why does open-iscsi initiator make SCSI commands fail instead of
reporting disk removal ?

$ sg_inq /dev/disk/by-path/ip-192.168.3.114\:3260-iscsi-...:tgt-lun-0
| grep RMB
  PQual=0  Device_type=0  RMB=0  version=0x05  [SPC-3]

Fubo.

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