DRBD Performance (draft)

DRBD can be used as RAID 1 but still couldn’t perform as well. More than RAID1, its performance rely strongly on hardware performance.

Let’s break DRBD replication into steps:

1. Data transfer through network:

Plus having a good bandwidth, DRBD documentation suggest some parameter to fine tune the net performance such as:

– The rate of synchronization,

– Using checksum-based synchronization,

– Replication modes,

2. Read/write data on the disk:

When I deployed DRBD, I had 2*8To SSD and gigabyte ethernet card and still not statisfied. To tackle I/O latency, you should consider at least two parameter:

– The I/O scheduler as it comes between DRBD binary and the disk:

The official docs suggest using the deadline I/O scheduler, although I think DRBD replication(RAID1 like) uses extensive write operations and deadline does prefer read operations. For me, I’ve chosen no I/O scheduler because I used SSD disks and kernel I/O schedulers are here for HDD only xd.

– The read/write speed of the disk:

I used Bonnie++ in order to do a benchmark of the disks I may use, SSD, although are expensive,  are very good.

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