Re: raid1 round-robin scheduler

[konstantin <kkv@clodo.ru>]

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?
>>
>
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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?

-- 
WBR
Konstantin V. Krotov

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