What is difference of creating mirror with
1 ) mdadm ( mdadm --create --verbose /dev/md0 --level=mirror --raid-devices=2 /dev/sdb1 /dev/sdc1 --spare-devices=1 /dev/sdd1 )
and
2) dmsetup ( dmsetp create mirror )
Which one is better ?. and Pros and cons ?. Google is not helping much
/Suresh
-----Original Message-----
From: Marian Csontos [mailto:mcsontos@xxxxxxxxxx]
Sent: Tuesday, January 27, 2015 12:32 AM
To: dm-devel@xxxxxxxxxx
Subject: Re: dm_mirror/dm_raid1 limitations ?.
On 01/26/2015 04:34 PM, suresh.babu.kandukuru@xxxxxxxxxx wrote:
> Heinzm,thanks for the quick reply.. We are using dmestup create mirror
> ..as we want to do that on physical San lun (block devices) ... Not
> the one ( lv create ) you mentioned below.. Is there any advantage
> going with logical volume approach lvcreate -type
One of LVM features is monitoring of mirror/raid LVs and removing/replacing any missing legs.
Using dmsetup directly, you have to do this manually.
>
> /Suresh
>
> Sent from my iPhone
>
>> On Jan 26, 2015, at 7:46 PM, Heinz Mauelshagen <heinzm@xxxxxxxxxx>
>> wrote:
>>
>>
>>> On 01/26/2015 02:51 PM, Suresh Babu Kandukuru wrote: Use case is
>>> : Two luns are mapped from storage array to linux host which are in
>>> same SAN fabric . we want to create a mirror on the linux host with
>>> these two luns and let host use that mirror lun . basic tests
>>> suggest that dm_mirror working fine . when we have any intermittent
>>> path issues with between host and san array , host i/o just freeze ,
>>> never returns back even after the path is online.
>>
>> Hard to tell what's happening without any kernel log.
>>
>>>
>>> Is dm_mirror viable solution here ?. Can you point me any link
>>> which gives the limitations of dm_mirror ? . another alternate
>>> solutions you propose here ?. Thanks in advance .
>>
>> We've switched the default away from "mirror" to "raid1" in order to
>> take advantage of th MD runtime. Have you tested "lvcreate --type
>> raid1 ..." yet? Please do.
>>
>> Regards, Heinz
>>
>>>
>>> Thanks /Suresh
>>>
>>>
>>> -- dm-devel mailing list dm-devel@xxxxxxxxxx
>>> https://www.redhat.com/mailman/listinfo/dm-devel
>>
>> <Untitled.txt>
>
>
>
> -- dm-devel mailing list dm-devel@xxxxxxxxxx
> https://www.redhat.com/mailman/listinfo/dm-devel
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