I have 3x 14TB toshiba drives mdadm-ed (
/dev/md0) raid 5'd together that are setup as a bcache. I have a 256GB fast SSD as the front of the bache.
write-back is enabled on bcache.
After a few days, the device (
/dev/bcache0) becomes extremely slow. I mean like 1000th of it's normal speed.
My 2 questions are:
For /dev/md0, what tuning should I do for those toshiba drives? It's 4k chunks 64k blocks.
Is there any bcache tuning I could do?
I'm not even really sure what other info I should put here. But if you ask, I'll update this post. Thanks!
Update 1- my IOSTAT while getting 100mb/sec read, only 3mb/sec write: https://pastebin.com/wKKf4LTq
The computer is an amd 2990wx w/32gb ram. CPU isn't the issue.
My old 3770k from 2010ish would get hard better read and write speeds than this. It's got to be some sort of setting or tuning. Thanks!
Update 2- While the system is running normally, below is the hdparm output. hdparm takes to long to run when it's not running normally.
/dev/md0: Timing cached reads: 11148 MB in 2.00 seconds = 5578.33 MB/sec Timing buffered disk reads: 1372 MB in 3.00 seconds = 456.84 MB/sec /dev/bcache0: Timing cached reads: 12564 MB in 2.00 seconds = 6286.57 MB/sec Timing buffered disk reads: 1226 MB in 3.00 seconds = 408.66 MB/sec