[dm-devel] RHEL6.6 dm-cache and dm-era
Romu Hu
huruomu at gmail.com
Fri Sep 26 03:16:41 UTC 2014
On 2014/9/25 22:57, Heinz Mauelshagen wrote:
> Romu,
>
> "dmsetup create MyEra --table "0 20971520 /dev/mapper/mpathbp1
> /dev/mapper/mpathap1 8"
>
> should read
>
> dmsetup create MyEra --table "0 20971520 era /dev/mapper/mpathbp1
> /dev/mapper/mpathap1 8"
Sorry my bad.
I ran 'dmsetup create MyEra --table "0 20971520 era /dev/mapper/mpathbp1
/dev/mapper/mpathap1 8"' but kernel (2.6.32-494.el6.i686) oopsed:
Sep 25 18:34:11 localhost kernel: device-mapper: era: sb_check failed:
magic 0: wanted 2126579579
Sep 25 18:34:11 localhost kernel: device-mapper: block manager:
superblock validator check failed for block 0
Sep 25 18:34:11 localhost kernel: device-mapper: era: couldn't read_lock
superblock
Sep 25 18:34:11 localhost kernel: BUG: unable to handle kernel NULL
pointer dereference at 00000008
Sep 25 18:34:11 localhost kernel: IP: [<f7e2b3c7>] era_destroy+0x7/0x60
[dm_era]Sep 25 18:34:11 localhost kernel: *pdpt = 0000000032457001 *pde
= 00000003fb5fa067
Sep 25 18:34:11 localhost kernel: Oops: 0000 [#1] SMP
Sep 25 18:34:11 localhost kernel: last sysfs file:
/sys/module/dm_persistent_data/initstate
Perhaps this should be cherry-picked?
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=989f26f5ad308f40a95f280bf9cd75e558d4f18d
The log says sb_check failed, anything wrong with the dmsetup command
parameters?
Thanks
Romu
> On 09/25/2014 04:02 PM, Romu wrote:
>> 2014-09-25 18:19 GMT+08:00 Heinz Mauelshagen <heinzm at redhat.com
>> <mailto:heinzm at redhat.com>>:
>>
>> On 09/25/2014 08:10 AM, Romu Hu wrote:
>>> On 2014/9/24 12:10, Brassow Jonathan wrote:
>>>> On Sep 22, 2014, at 7:35 AM, Romu wrote:
>>>>
>>>>> I tried the following command to set up my era target but the
>>>>> command immediately panics the system and the system reboots.
>>>>>
>>>>> # dmsetup create MyEra --table "0 41941903 era
>>>>> /dev/mapper/VG-CacheDataLV_cmeta /dev/mapper/VG-OriginLV 4096"
>>>>>
>>>>> The metadata dev and the origin dev are all part of a LVM
>>>>> cache LV. VG-CacheDataLV_cmeta is the cache metadata LV on the
>>>>> smaller and faster device, VG-OriginLV is the origin LV on the
>>>>> faster and slower device, 41941903 is the total sector number
>>>>> of the device of OriginLV (the LV takes 100% space of the
>>>>> device), 4096 is the block size of OriginLV, I have run
>>>>> 'mkfs.ext4 /dev/mapper/VG-OriginLV' before running the dmsetup
>>>>> command.
>>>>>
>>>>> Below is the message in /var/log/messages after running the
>>>>> dmsetup comnmand:
>>>>>
>>>>> kernel: device-mapper: era: sb_check failed: magic 1623043:
>>>>> wanted 2126579579 <tel:2126579579>
>>>>> kernel: device-mapper: block manager: superblock validator
>>>>> check failed for block 0
>>>>> kernel: device-mapper: era: couldn't read_lock superblock
>>>>>
>>>>>
>>>>> Any idea?
>>>>>
>>>>
>>>> Sorry, I haven't used dm-era yet. However, it does appear that
>>>> you are perhaps specifying the wrong devices when creating the
>>>> era device? Looks like you might be allowing the era target
>>>> and the cache target to use the same metadata area at the same
>>>> time - causing them to corrupt each other's metadata area?
>>>>
>>>> brassow
>>>
>>> I think the dmsetup command to set up an era target should be
>>> something like this:
>>>
>>> # dmsetup create MyEra --table "0 sector_number era metadeta_dev
>>> origin_dev block_size"
>>>
>>> My questions:
>>>
>>> 1) How to calculate sector_number? According to
>>> https://www.kernel.org/doc/Documentation/device-mapper/era.txt,
>>> I guess it should be (4 * nr_blocks) bytes + buffers, but what
>>> is nr_blocks and what is buffers?
>>
>> No calculation: it's the size of your era target in sectors.
>> Typically "blockdev --getsz origin_dev"
>>
>>> 2) Any documentation for dmsetup tables?
>>
>> Look for examples in the kernel source trees
>> Documentaion/device.mapper.
>>
>> table line syntax is: "start_sector length_in_sectors <target>
>> <target_arguments{0,N}>"
>>
>>> 3) Both my metadata_dev and origin_dev are 10G partitions, is
>>> this all right?
>>
>> Metadata device size is plenty but that depends on how many eras
>> with how many updates you want to have.
>>
>>> 4) My origin_dev is a ext4 filesystem with a block size of 4096,
>>> so the block_size in the command line should also be 4096?
>>
>> You may use 4096 = _8_ sectors, you used 4096 sectors = 2MB below.
>> It's the granularity the era target housekeeps blocks for.
>>
>>>
>>> I tried the following command:
>>>
>>> # dmsetup create MyEra --table "0 160000 era
>>> /dev/mapper/mpathap1 /dev/mapper/mpathbp1 4096"
>>
>> May not be same physical device for data and metadata!
>> If it is, thta'd explain your oops.
>>
>> # dmsetup create MyEra --table "0 $(blockdev --getsz
>> /dev/mapper/mpathbp) era whatever_disctinct_metadata_device
>> /dev/mapper/mpathbp1 8"
>>
>> Would use 8 sector block size (which is tiny!) with disctinct
>> metadata and data devices (presumabyl your ext4 sits on
>> /dev/mapper/mpathbp1)
>>
>> Heinz
>>
>>
>> Heinz, thank you for your help!
>>
>> My origin dev is 10G so total sector number is 20971520.
>> /dev/mapper/mpathbp1 (/dev/dm-6) is the metadata dev,
>> /dev/mapper/mpathap1 (/dev/dm-7) is the origin dev, they are on
>> different LUNs.
>>
>> I tried the following commands:
>>
>> # dmsetup create MyEra --table "0 20971520 /dev/mapper/mpathbp1
>> /dev/mapper/mpathap1 8"
>> # Target type name /dev/mapper/mpathbp1 is too long.
>> # Command failed
>>
>> # dmsetup create MyEra --table "0 20971520 /dev/dm-6 /dev/dm-7 8"
>> # device-mapper: reload ioctl on MyEra failed: Invalid argument
>> # Command failed
>>
>> And when executing the second command I see the following in
>> /var/log/messages:
>>
>> Sep 25 06:37:48 localhost kernel: device-mapper: table: 253:8:
>> /dev/dm-6: unknown target type
>> Sep 25 06:37:48 localhost kernel: device-mapper: ioctl: error adding
>> target to table
>> Sep 25 06:37:48 localhost multipathd: dm-8: remove map (uevent)
>> Sep 25 06:37:48 localhost multipathd: dm-8: devmap not registered,
>> can't remove
>> Sep 25 06:37:48 localhost multipathd: dm-8: remove map (uevent)
>> Sep 25 06:37:48 localhost multipathd: dm-8: devmap not registered,
>> can't remove
>>
>> Then I run 'mkfs.ext4 /dev/dm-6' and tried the second command again
>> but got the same result.
>>
>> Any idea?
>>
>> Thanks
>> Romu
>>
>>
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>
>
>
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