[DRBD-user] IO vs Safety

Miloš Kozák milos.kozak at lejmr.com
Mon Oct 7 21:07:31 CEST 2013

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

I am wondering about an optimal DRBD configuration. Currently I have got 
two identical servers containing two HDDs each for data. Two HDDs are in 
RAID 1 (md127). These two md127 are mirrored using drbd. it works 
perfectly but I am wondering about its performance. Since RAID 1 
decreseses write performence having two RAID1 (mdadm and drbd) must 
decrese write performance even more. Say It makes around aprox 20 IOPS 
from 4x 75IOPS SATA 7200rpm HDDs? Am I right? If that is true is there a 
way out of there?

I was wondering if it is viable to use only one RAID1. I would use DRBD 
for RAID 1 between two servers, hence from these 4 HDDs I would make 
RAID 10 where RAID 1 is created using DRBD and RAID 0 using mdadm..

However there is a thing I am not sure about. What happens I one disk 
failes? Is it same for drbd as for mdadm? I just replace HDD and 
everything runs smoothly forward? What if I need to reboot system meanwhile?

Thanks for answers,

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