Comments on: TIER OPTIMIZATION EFFECTS

By: Andrew Thrift

Andrew Thrift — Thu, 09 Aug 2012 00:37:29 +0000

Dimi, Kent, why dont you take the best parts of both your projects and work on this together. Surely 2 minds are better than 1

Great work from both of you, Tire and bcache are awesome projects and sorely needed.

By: Kent Overstreet

Kent Overstreet — Thu, 26 Jul 2012 00:43:58 +0000

Oh yeah, looked at your code a bit and you’re using a rb tree for lookups. That’s gonna limit you hard on random read iops.

Impresive what you’ve done in under 3k lines of code, though.

By: Kent Overstreet

Kent Overstreet — Thu, 26 Jul 2012 00:41:16 +0000

Hey, bcache author here.

Curious how you had bcache configured. Those numbers look low compared to what it’s capable of.

Probably either the default settings should be changed, or I need to go looking for performance bugs. Or likely both.

The iodepth you’re running fio with is also way lower than what I normally test with. Would like to see how bcache and tier compare as it’s cranked up.

Also, probably the area I’ve put the most effort into optimizing is random reads from cache – as long as you’re showing off random reads on a warm cache with tier, you should show bcache too

If you shoot me an email I’d like to compare notes – I couldn’t find yours.

By: dimitri

dimitri — Mon, 09 Jul 2012 14:53:17 +0000

Hi Mark
Thanks i think is very useful before other solution to the problem

By: maru

maru — Mon, 09 Jul 2012 14:03:24 +0000

Hi Dimi,

I had the same idea. I’ll allow starting and stopping data migration via sysfs.
echo 1 >/sys/block/tiera/enable_optimization or something like it.

By: dimi

dimi — Mon, 09 Jul 2012 12:20:22 +0000

Hi Mark
to partial solve the concurrent High Load and Data Tier migration is to have a command to force “Migrate Data” and “Stop Migration”.
Do you think is possible?
Thanks so much