Re: [linux-lvm] what is the IOPS behavior when partitions of single disk(raid5 backend) are used in an LVM?

[Sherpa Sherpa <norbuurgen@gmail.com>]

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Thank you for reply i dont mind if fstab sees partitions.  I read this "To
avoid striping performance
 problems LVM can't tell that two PVs are on the same physical disk, so if
you create a striped LV then the stripes could be on different partitions  on
the same disk resulting in a *decrease* in performance rather than an
increase."
in the tldp.org but does this apply to disks made from RAID backend ?

Warm Regards
Urgen Sherpa


On Fri, Oct 12, 2018 at 9:09 PM Heinz Mauelshagen <heinzm@redhat.com> wrote:

> On 10/11/18 4:31 PM, Emmanuel Gelati wrote:
>
> If you use sdb only for data, you don't have need to use partition on the
> disk.
>
> Though that's true, keeping 1 partition per disk for each LVM PV adds
> additional
> 'visibility' by tools like fdisk/[cs]fdisk, parted etc. showing the
> partition type to be 'Liinux LVM'.
>
> Using the whole disk, blkid or lsblk will provide that information still,
> e.g. 'blkid --match-token TYPE=LVM2_member'.
>
> Heinz
>
>
> Il giorno gio 11 ott 2018 alle ore 16:26 David Teigland <
> teigland@redhat.com> ha scritto:
>
>> On Thu, Oct 11, 2018 at 08:53:07AM +0545, Sherpa Sherpa wrote:
>> > I have LVM(backed by hardware RAID5) with logical volume and a volume
>> group
>> > named "dbstore-lv" and "dbstore-vg" which have sdb1 sdb2 sdb3 created
>> from
>> > same sdb disk.
>>
>> > sdb                                8:16   0  19.7T  0 disk
>> > ├─sdb1                             8:17   0   7.7T  0 part
>> > │ └─dbstore-lv (dm-1)              252:1    0   9.4T  0 lvm
>> /var/db/st01
>> > ├─sdb2                             8:18   0   1.7T  0 part
>> > │ └─dbstore-lv (dm-1)              252:1    0   9.4T  0 lvm
>> /var/db/st01
>> > └─sdb3                             8:19   0  10.3T  0 part
>> >   └─archive--archivedbstore--lv (dm-0)     252:0    0  10.3T  0 lvm
>>
>> > I am assuming this is due to disk seek problem as the same disk
>> partitions
>> > are used for same LVM or may be its due to saturation of the disks
>>
>> You shouldn't add different partitions as different PVs.  If it's too late
>> to fix, it might help to create new LV that uses only one of the
>> partitions, e.g. lvcreate -n lv -L size vg /dev/sdb2, and then copy your
>> current LV to the new one.
>>
>> _______________________________________________
>> 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/
>
>
>
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