[dm-devel] info on enabling only one path with rdac and DS4700

[Gianluca Cecchi]

On Mon, Nov 28, 2011 at 3:46 PM, Moger, Babu wrote:
>> 3) Based on messages during failover, is it true that I can avoid
>> explicitly put scsi_dh in initrd?
>> If I create initrd this way:
>> mkinitrd /boot/initrd-$(uname -r)-scsi_dh.img $(uname -r) --
>> preload=scsi_dh_rdac
>> I get this difference:
>> [root at testserver ~]# diff /tmp/new/init /tmp/current/init
>> 44,51d43
>> < echo "Loading scsi_mod.ko module"
>> < insmod /lib/scsi_mod.ko
>> < echo "Loading sd_mod.ko module"
>> < insmod /lib/sd_mod.ko
>> < echo "Loading scsi_dh.ko module"
>> < insmod /lib/scsi_dh.ko
>> < echo "Loading scsi_dh_rdac.ko module"
>> < insmod /lib/scsi_dh_rdac.ko
>> 62a55,58
>> > echo "Loading scsi_mod.ko module"
>> > insmod /lib/scsi_mod.ko
>> > echo "Loading sd_mod.ko module"
>> > insmod /lib/sd_mod.ko
>>
>> or will it help in any way?
>
> Having scsi_dh_rdac in initrd will help to get rid of the initial I/O errors you are seeing.
>

Actually not.... see screen shots of console start at
https://docs.google.com/open?id=0BwoPbcrMv8mvMWRlYmVhM2MtY2JkYi00ZDMzLWIxMWMtMDM0YzZjMWU0NGE1
and
https://docs.google.com/open?id=0BwoPbcrMv8mvM2RjMDg1MWUtYzVmZC00OTA1LTljNjAtZGZmMjM5NDlhYTI4
and also dmesg giving for example for sdb and sdc:

scsi 3:0:0:1: rdac: LUN 1 (unowned)
sdb : very big device. try to use READ CAPACITY(16).
SCSI device sdb: 7320494080 512-byte hdwr sectors (3748093 MB)
sdb: Write Protect is off
sdb: Mode Sense: 77 00 10 08
SCSI device sdb: drive cache: write back w/ FUA
sdb : very big device. try to use READ CAPACITY(16).
SCSI device sdb: 7320494080 512-byte hdwr sectors (3748093 MB)
sdb: Write Protect is off
sdb: Mode Sense: 77 00 10 08
SCSI device sdb: drive cache: write back w/ FUA
 sdb:<3>Buffer I/O error on device sdb, logical block 0
Buffer I/O error on device sdb, logical block 0
Buffer I/O error on device sdb, logical block 0
Buffer I/O error on device sdb, logical block 0
Buffer I/O error on device sdb, logical block 0
Buffer I/O error on device sdb, logical block 0
Buffer I/O error on device sdb, logical block 0
Dev sdb: unable to read RDB block 0
Buffer I/O error on device sdb, logical block 0
Buffer I/O error on device sdb, logical block 0
 unable to read partition table
sd 3:0:0:1: Attached scsi disk sdb
  Vendor: IBM       Model: 1814      FAStT   Rev: 0916
  Type:   Direct-Access                      ANSI SCSI revision: 05
scsi 3:0:1:1: rdac: LUN 1 (owned)
scsi 3:0:1:1: rdac: LUN 1 (owned)
sdc : very big device. try to use READ CAPACITY(16).
SCSI device sdc: 7320494080 512-byte hdwr sectors (3748093 MB)
sdc: Write Protect is off
sdc: Mode Sense: 77 00 10 08
SCSI device sdc: drive cache: write back w/ FUA
sdc : very big device. try to use READ CAPACITY(16).
SCSI device sdc: 7320494080 512-byte hdwr sectors (3748093 MB)
sdc: Write Protect is off
sdc: Mode Sense: 77 00 10 08
SCSI device sdc: drive cache: write back w/ FUA
 sdc: unknown partition table
sd 3:0:1:1: Attached scsi disk sdc
...
GSI 23 sharing vector 0x72 and IRQ 23
ACPI: PCI Interrupt 0000:04:00.0[A] -> GSI 17 (level, low) -> IRQ 114
eth0: Broadcom NetXtreme II BCM5708 1000Base-SX (B2) PCI-X 64-bit
133MHz found at mem da000000, IRQ 114, node addr 00215e2fd0e2
ACPI: PCI Interrupt 0000:06:00.0[A] -> GSI 19 (level, low) -> IRQ 90
eth1: Broadcom NetXtreme II BCM5708 1000Base-SX (B2) PCI-X 64-bit
133MHz found at mem d8000000, IRQ 90, node addr 00215e2fd0e4
printk: 69 messages suppressed.
Buffer I/O error on device sdb, logical block 0
...
md: Autodetecting RAID arrays.
md: autorun ...
md: ... autorun DONE.
device-mapper: multipath: version 1.0.6 loaded
device-mapper: multipath: Using scsi_dh module scsi_dh_rdac for
failover/failback and device management.
device-mapper: multipath round-robin: version 1.0.0 loaded
printk: 4 messages suppressed.
Buffer I/O error on device sdb, logical block 915061759
...

So if I have to get yet the I/O errors, having no advantage, I'd
prefer to stay stick with the default initrd...