dm-cache issue:unable to create cache

[Nitin Kshirsagar]

Hello Joe,

I have setup dm-cache and tried to create cache but it fails with error message "device-mapper: reload ioctl failed".

Issue:Create cache fails
--------------------------------------------------------------------------------------------------------
Steps:
1.Check list of devices
[root@localhost dm-cache]# blockdev --report
RO RA SSZ BSZ StartSec Size Device
rw 256 512 4096 0 42949672960 /dev/sda
rw 256 512 1024 2048 209715200 /dev/sda1
rw 256 512 4096 411648 2147483648 /dev/sda2
rw 256 512 4096 4605952 40591425536 /dev/sda3
rw 256 512 4096 0 17179869184 /dev/sdb
rw 256 512 4096 0 10737418240 /dev/sdc
rw 256 512 4096 0 10737418240 /dev/sdd
rw 256 512 4096 0 21474836480 /dev/sde
rw 256 512 4096 0 10737418240 /dev/sdf
rw 256 512 4096 0 16106127360 /dev/sdg

2. Try to create cache
[root@localhost dm-cache]# ./dmc-setup.pl -o /dev/sdb -c /dev/sdc -n c1
Operator or semicolon missing before &__inline at (eval 104) line 1.
Ambiguous use of & resolved as operator & at (eval 104) line 1.
echo 0 33554432 cache /dev/sdb /dev/sdc 0 8 65536 16 0 | dmsetup create c1
device-mapper: reload ioctl failed: No such file or directory
Command failed
[root@localhost dm-cache]# echo $?
1
[root@localhost dm-cache]# lsmod | grep dm
dm_cache 32666 0
dm_bio_prison 6617 1 dm_cache
dm_persistent_data 54713 1 dm_cache
dm_bufio 19555 1 dm_persistent_data
dm_mod 83573 3 dm_cache,dm_persistent_data,dm_bufio

[root@localhost dm-cache]# dmesg
device-mapper: table: 253:0: cache: Error opening origin device
device-mapper: ioctl: error adding target to table
device-mapper: table: 253:0: cache: Error opening origin device
device-mapper: ioctl: error adding target to table


--
Thanks & Regards

Nitin Kshirsagar
Software Engr, QA
Cell 997.566.3985

STEC india private Limited, Pune | The SSD Company TM
NASDAQ STEC • Web www.stec-inc.com

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[thor...@redhat.com]

Hi Nitin,

On Thu, Jan 24, 2013 at 08:46:51PM +0800, Nitin Kshirsagar wrote:
> Hello Joe,
>
> I have setup dm-cache and tried to create cache but it fails with error message "device-mapper: reload ioctl failed".
>

> 2. Try to create cache
> [root@localhost dm-cache]# ./dmc-setup.pl -o /dev/sdb -c /dev/sdc -n c1
> Operator or semicolon missing before &__inline at (eval 104) line 1.
> Ambiguous use of & resolved as operator & at (eval 104) line 1.

what are these errors?

> echo 0 33554432 cache /dev/sdb /dev/sdc 0 8 65536 16 0 | dmsetup create c1

That line is just wrong, you're giving '0' as the origin for a start.
Here's a table from one of my test scripts:

0 4194304 cache /dev/mapper/test-dev-844037 /dev/mapper/test-dev-858816 /dev/mapper/test-dev-3453 512 0 mq 0

And here's a summary of the target line:

/*
* Construct a cache device mapping.
*
* cache <metadata dev> <cache dev> <origin dev> <block size>
* <#feature_args> [<arg>]* <policy> <#policy_args> [<arg>]*
*
* metadata dev : fast device holding the persistent metadata
* cache dev : fast device holding cached data blocks
* origin dev : slow device holding original data blocks
* block size : cache unit size in sectors
* #feature args [<arg>]* : number of feature arguments followed by
* optional arguments * cache dev
* policy : the replacement policy to use
* #policy_args [<arg>]* : number of policy arguments followed by optional
* arguments; see policy plugin for instances
* (key value pairs count as 2; delimiter is space)
*
* Optional feature arguments are:
* writeback: write back cache allowing cache block contents to
* differ from origin blocks for performance reasons
* writethrough: write through caching prohibiting cache block
* content from being distinct from origin block content
*/


Hope that helps,

- Joe