[linux-lvm] Why is my LVM Mirror performance so bad?
Micky
mickylmartin at gmail.com
Sat Sep 27 20:35:24 UTC 2014
Because it is LVM! :)
On Sat, Sep 27, 2014 at 10:42 PM, Errol Neal <eneal at businessgrade.com>
wrote:
> Hi There. Hoping to get some clarity on some performance woes in a little
> testing environment that I've setup.
>
> I am experimenting with LVM mirrors on a CentOS 6.5 cluster.
>
> I have two VMs running on ESX5.5 that are sharing two RDM luns from an SRP
> target server running SCST.
>
> Performance however seems to take a huge hit compared to a vanilla volume
>
>
> [root at scst1 ~]# vgs
> VG #PV #LV #SN Attr VSize VFree
> hadata 2 5 0 wz--nc 999.99g 149.99g
> vg_scst1 1 2 0 wz--n- 39.51g 0
>
> [root at scst1 ~]# lvs -a -o +devices
> LV VG Attr LSize Pool Origin Data% Move
> Log Cpy%Sync Convert Devices
> mirror1 hadata mwi-a-m--- 100.00g
> 100.00 mirror1_mimage_0(0),mirror1_mimage_1(0)
> [mirror1_mimage_0] hadata iwi-aom--- 100.00g
> /dev/sdb1(0)
> [mirror1_mimage_1] hadata iwi-aom--- 100.00g
> /dev/sdc1(0)
> mirror2 hadata mwi-a-m--- 100.00g
> 100.00 mirror2_mimage_0(0),mirror2_mimage_1(0)
> [mirror2_mimage_0] hadata iwi-aom--- 100.00g
> /dev/sdb1(25600)
> [mirror2_mimage_1] hadata iwi-aom--- 100.00g
> /dev/sdc1(25600)
> mirror3 hadata mwi-a-m--- 100.00g
> 100.00 mirror3_mimage_0(0),mirror3_mimage_1(0)
> [mirror3_mimage_0] hadata iwi-aom--- 100.00g
> /dev/sdb1(51200)
> [mirror3_mimage_1] hadata iwi-aom--- 100.00g
> /dev/sdc1(51200)
> mirror4 hadata mwi-a-m--- 100.00g
> 100.00 mirror4_mimage_0(0),mirror4_mimage_1(0)
> [mirror4_mimage_0] hadata iwi-aom--- 100.00g
> /dev/sdb1(76800)
> [mirror4_mimage_1] hadata iwi-aom--- 100.00g
> /dev/sdc1(76800)
> test hadata -wi-a----- 50.00g
> /dev/sdb1(102400)
> lv_root vg_scst1 -wi-ao---- 31.65g
> /dev/sda2(0)
> lv_swap vg_scst1 -wi-ao---- 7.86g
> /dev/sda2(8102)
>
> [root at scst1 ~]# dd if=/dev/sdb1 of=/dev/null bs=1M count=20000
> 20000+0 records in
> 20000+0 records out
> 20971520000 bytes (21 GB) copied, 41.0031 s, 511 MB/s
>
> [root at scst1 ~]# dd if=/dev/hadata/test of=/dev/null bs=1M count=20000
> 20000+0 records in
> 20000+0 records out
> 20971520000 bytes (21 GB) copied, 44.344 s, 473 MB/s
>
> [root at scst1 ~]# dd if=/dev/hadata/mirror1 of=/dev/null bs=1M count=20000
> 20000+0 records in
> 20000+0 records out
> 20971520000 bytes (21 GB) copied, 365.685 s, 57.3 MB/s
>
>
> Is this just the life of a LVM mirror and the performance here is about as
> good as it gets?
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm at 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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