[DRBD-user] DRBD fsync() seems to return before writing to disk

Shaun Thomas sthomas at optionshouse.com
Thu Jun 21 19:08:47 CEST 2012

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


> Interesting. For 8 kB blocks, 703 kB/s means 87 IO/s, or
> 5272 IO/min. Sounds like a 7200 RPM drive, with some overhead.

Nope. 10k RPM drives in this case. The 8k reads are small enough that they created a lot more journal traffic than you'd normally like. A watched iostat showed about 165 IOPS, which is what you'd expect there.

> I'm having a hard time thinking of a way to test your RAID
> controller's behavior that isn't harder than just testing on
> a regular SATA drive, which has caching semantics that are well
> known.

Unfortunately no machine I have access to has just plain drives to confirm results like you're claiming. Every cache/writethrough/flushing combo I've thrown at it reacted as expected in our case. I tried though.  :)

Maybe someone with a regular old desktop and 7200 RPM drives will pipe in eventually, but I'm out of ideas. I'm willing to wager it's just your setup though. For one reason or another.



______________________________________________

See http://www.peak6.com/email_disclaimer/ for terms and conditions related to this email



More information about the drbd-user mailing list