[linux-lvm] lvm mirror read performance, no load balance with PV ?

[linux-lvm] lvm mirror read performance, no load balance with PV ?

[Sascha Thomas Spreitzer]

Hello mailing list,

I currently sensed that LVM2 is not load balancing reads of mirrored
LV's form their corresponding PV.

PV1     PV2
LV        LV'
IO=0    IO=90MB/s

[~]# lvm version
  LVM version:     2.02.39 (2008-06-27)
  Library version: 1.02.27 (2008-06-25)
  Driver version:  4.14.0

Distribution is Fedora 10, updated.

Is this normal behaviour, or did a make a big mistake in my configuration?

FYI:

[~]# pvs -o+lv_name,lv_size,lv_attr
  PV         VG         Fmt  Attr PSize   PFree LV                LSize   Attr
  /dev/sda2  VolGroup00 lvm2 a-   145,22G 4,97G [lvroot_mlog]      32,00M lwi-ao
  /dev/sda2  VolGroup00 lvm2 a-   145,22G 4,97G [lvhome_mlog]      32,00M lwi-ao
  /dev/sda2  VolGroup00 lvm2 a-   145,22G 4,97G lvdata            285,50G -wi-ao
  /dev/sda2  VolGroup00 lvm2 a-   145,22G 4,97G [lvswap_mlog]      32,00M lwi-ao
  /dev/sda2  VolGroup00 lvm2 a-   145,22G 4,97G                        0
  /dev/sda3  VolGroup00 lvm2 a-   553,28G    0  [lvswap_mimage_1]   5,03G iwi-ao
  /dev/sda3  VolGroup00 lvm2 a-   553,28G    0  [lvroot_mimage_1]  15,00G iwi-ao
  /dev/sda3  VolGroup00 lvm2 a-   553,28G    0  [lvhome_mimage_1] 533,25G iwi-ao
  /dev/sdb1  VolGroup00 lvm2 a-   698,62G    0  [lvswap_mimage_0]   5,03G iwi-ao
  /dev/sdb1  VolGroup00 lvm2 a-   698,62G    0  [lvroot_mimage_0]  15,00G iwi-ao
  /dev/sdb1  VolGroup00 lvm2 a-   698,62G    0  [lvhome_mimage_0] 533,25G iwi-ao
  /dev/sdb1  VolGroup00 lvm2 a-   698,62G    0  lvdata            285,50G -wi-ao

-- 
Mit freundlichen Gr��en, / with kind regards,
Sascha Thomas Spreitzer
http://spreitzer.name/

Re: [linux-lvm] lvm mirror read performance, no load balance with PV ?

[malahal]

Sascha Thomas Spreitzer [sascha@spreitzer.name] wrote:
> Hello mailing list,
> 
> I currently sensed that LVM2 is not load balancing reads of mirrored
> LV's form their corresponding PV.

Yes, it just reads from the default_mirror (i.e. primary mirror leg).
There is a read-balancing patch. It is not upstream yet and most likely
not there in your kernel either.

Thanks, Malahal.

Re: [linux-lvm] lvm mirror read performance, no load balance with PV ?

[Sascha Thomas Spreitzer]

Hello Malahal,

I'm impressed, are there any reasons this patch has not been committed yet?

regards,
Sascha

2009/3/24  <malahal@us.ibm.com>:
> Sascha Thomas Spreitzer [sascha@spreitzer.name] wrote:
>> Hello mailing list,
>>
>> I currently sensed that LVM2 is not load balancing reads of mirrored
>> LV's form their corresponding PV.
>
> Yes, it just reads from the default_mirror (i.e. primary mirror leg).
> There is a read-balancing patch. It is not upstream yet and most likely
> not there in your kernel either.
>
> Thanks, Malahal.
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>



-- 
Mit freundlichen Gr��en, / with kind regards,
Sascha Thomas Spreitzer
http://spreitzer.name/

Re: [linux-lvm] lvm mirror read performance, no load balance with PV ?

[malahal]

Sascha Thomas Spreitzer [sascha@spreitzer.name] wrote:
> Hello Malahal,
> 
> I'm impressed, are there any reasons this patch has not been committed yet?
> 
> regards, Sascha

No one really needed up until now, I guess! Ask dm-devel mailing for
actual reason(s).


Thanks, Malahal.

Re: [linux-lvm] lvm mirror read performance, no load balance with PV ?

[Sascha Thomas Spreitzer]

Can you give me a reference to this patch first? URL?

2009/3/24  <malahal@us.ibm.com>:
> Sascha Thomas Spreitzer [sascha@spreitzer.name] wrote:
>> Hello Malahal,
>>
>> I'm impressed, are there any reasons this patch has not been committed yet?
>>
>> regards, Sascha
>
> No one really needed up until now, I guess! Ask dm-devel mailing for
> actual reason(s).
>
>
> Thanks, Malahal.
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>



-- 
Mit freundlichen Gr��en, / with kind regards,
Sascha Thomas Spreitzer
http://spreitzer.name/

Re: [linux-lvm] lvm mirror read performance, no load balance with PV ?

[malahal]

Sascha Thomas Spreitzer [sascha@spreitzer.name] wrote:
> Can you give me a reference to this patch first? URL?

See the following link. If you read the responses, then you know why it
is not in upstream yet. 

http://permalink.gmane.org/gmane.linux.kernel.device-mapper.devel/2415

Thanks, Malahal.

Re: [linux-lvm] lvm mirror read performance, no load balance with PV ?

[Sascha Thomas Spreitzer]

Hello Malahal,

thank you very much, I will try to get this upstream, imho. such a
feature should not be missing.

regards,
Sascha

2009/3/26  <malahal@us.ibm.com>:
> Sascha Thomas Spreitzer [sascha@spreitzer.name] wrote:
>> Can you give me a reference to this patch first? URL?
>
> See the following link. If you read the responses, then you know why it
> is not in upstream yet.
>
> http://permalink.gmane.org/gmane.linux.kernel.device-mapper.devel/2415
>
> Thanks, Malahal.
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>



-- 
Mit freundlichen Gr��en, / with kind regards,
Sascha Thomas Spreitzer
http://spreitzer.name/