[sheepdog-users] Sheepdog 0.6.0 schedule and todos

Liu Yuan namei.unix at gmail.com
Tue Nov 6 09:32:06 CET 2012

On 11/06/2012 04:10 PM, Alexandre DERUMIER wrote:
> One thing that could be great with journal, is something like slog
> device with zfs or nvram with netapp san.

Currently I am writing it. To be honest, I have no idea of zfs and
netapp san.

The idea is that we log ahead all the updates of object in another
device (be it a HHD or SSD or nvram) sequentially and use buffered
IO/direct IO for actual data updates without 'O_DSYNC' flag.

I got 80x times faster even with another HDD as journal device on my test.

See more info at

> random writes are going to a fast journal (ssd, nvram,...) then are
> flushed sequentially each X seconds to slower disks.

The log write will currently is with O_DSYNC | O_DIRECT flag to assure
data integrity. I will consider group commit to accelerate log write
later when basic function is stable.


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