bcache performance issue

Kernels & Hardware, configuring network, installing services

bcache performance issue

Postby codemaker » 2018-04-18 19:20

Hi,

I'm trying to setup a RAID10 mdadm array with bcache. My setup looks like this:

md0 -> bcache -> LVM

I'm using a RAID1 SSDs as the caching disks. The bcache mode is set to writeback. I test the writing speed using the following:
Code: Select all
dd if=/dev/zero of=/mnt/test/file bs=256M count=1 oflag=dsync
1+0 records in
1+0 records out
268435456 bytes (268 MB, 256 MiB) copied, 1.0099 s, 266 MB/s


I get slower speed compared to another RAID10 mdadm array I have with no bcache. Here is what I get running the same command on the RAID10 array without bcache:
Code: Select all
dd if=/dev/zero of=/mnt/test/file bs=256M count=1 oflag=dsync
1+0 records in
1+0 records out
268435456 bytes (268 MB) copied, 0.689868 s, 389 MB/s


As you can see, the array with bcache is considerably slower than the one with bcache. Any thoughts about the reason?

Forgot to mention that I'm on Debian Stretch.

Thanks for any ideas or help you can provide.
codemaker
 
Posts: 1
Joined: 2018-04-18 19:07

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