[CentOS] OT: Caching synchronous writes

Fri Apr 23 08:20:01 UTC 2010
Jure Pečar <pegasus at nerv.eu.org>

> > Ray Van Dolson wrote:
> > >> I think what you want is a proper storage array with mirrored write
> > >> cache.

When ext3 came into widespread use, a popular method to "cache" frequent fsyncs was to run it in a full data journaling mode, with external journal on a separate disk.
This turned all random writes to a sequential write, limited to a very small piece of disk and a periodical journal flush to the real file system.
This worked amazingly well for busy mail queues - throughput went up 10x and more. People were also reporting improvements in NFS scenarios. Don't know how this is relevant today in times of SSD, but it should be worth to test it.


Jure Pečar