Re: raid1 round-robin scheduler

[konstantin <kkv@clodo.ru>]

10.03.2015 17:22, Heinz Mauelshagen wrote:
>
> On 03/10/2015 12:55 PM, konstantin wrote:
>>
>>
>> 19.02.2015 18:02, Heinz Mauelshagen пишет:
>>>
>>>
>>> dm-mirror (i.e. "lvcreate --type mirror" or respective "dmsetup create
>>> --table ...",
>>> which is not the recommended raid1 layout any more) provides read
>>> round-robin since long time.
>>> You'd need an ancient kernel not to have it supported.
>>>
>>> "raid1"/"raid10" (the recommended targets) , i.e. the md-raid based
>>> mappings accessible via the dm-raid target
>>> do read optimizations as well. Use "lvcreate --type raid1/raid10 ..." or
>>> a respective dm table to set
>>> those up. The former ("raid1") is the default in modern distributions
>>> and configurable via setting
>>> 'mirror_segtype_default = "raid1"' in /etc/lvm/lvm.conf.
>>>
>>> Heinz
>>>
>>>
>>>
>>>
>>> On 02/19/2015 08:23 AM, konstantin wrote:
>>>> What version of the kernel should I use to get a round-robin read
>>>> implementation on LV raid1?
>>>>
>>>
>>> --
>>> dm-devel mailing list
>>> dm-devel@redhat.com
>>> https://www.redhat.com/mailman/listinfo/dm-devel
>>
>> I'm create raid1 lv with "lvcreate --type raid1 -m1 -L5G -n r1lv r1vg"
>> on vg with two physical devices:
>>
>> lvs -a -o +devices
>>   LV              VG   Attr     LSize Pool Origin Data%  Move Log
>> Copy%  Convert Devices
>>   r1lv            r1vg rwi-a-m- 5.00g 100.00
>> r1lv_rimage_0(0),r1lv_rimage_1(0)
>>   [r1lv_rimage_0] r1vg iwi-aor- 5.00g           /dev/sda(1)
>>   [r1lv_rimage_1] r1vg iwi-aor- 5.00g           /dev/sdb(1)
>>   [r1lv_rmeta_0]  r1vg ewi-aor- 4.00m           /dev/sda(0)
>>   [r1lv_rmeta_1]  r1vg ewi-aor- 4.00m           /dev/sdb(0)
>>
>> but, reading is only one of the devices (i see nmon live disk
>> utilization). There are solutions to ensure reading from the two devices?
>>
>
> How do you test?
> Do you read from multiple threads?
>
>
>
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really .. I used dd to test in one thread,
but why when I read in one thread I can not read from two PV devices at 
the same time?

-- 
WBR
Konstantin V. Krotov

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