Sorry for spam... I meant D_SYNC. On Mon, Jan 9, 2017 at 2:56 PM, Brian Andrus <[email protected]> wrote:
> Hi Willem, the SSDs are probably fine for backing OSDs, it's the O_DSYNC > writes they tend to lie about. > > They may have a failure rate higher than enterprise-grade SSDs, but are > otherwise suitable for use as OSDs if journals are placed elsewhere. > > On Mon, Jan 9, 2017 at 2:39 PM, Willem Jan Withagen <[email protected]> > wrote: > >> On 9-1-2017 18:46, Oliver Humpage wrote: >> > >> >> Why would you still be using journals when running fully OSDs on >> >> SSDs? >> > >> > In our case, we use cheaper large SSDs for the data (Samsung 850 Pro >> > 2TB), whose performance is excellent in the cluster, but as has been >> > pointed out in this thread can lose data if power is suddenly >> > removed. >> > >> > We therefore put journals onto SM863 SSDs (1 journal SSD per 3 OSD >> > SSDs), which are enterprise quality and have power outage protection. >> > This seems to balance speed, capacity, reliability and budget fairly >> > well. >> >> This would make me feel very uncomfortable..... >> >> So you have a reliable journal, so upto there thing do work: >> Once in the journal you data is safe. >> >> But then you async transfer the data to disk. And that is an SSD that >> lies to you? It will tell you that the data is written. But if you pull >> the power, then it turns out that the data is not really stored. >> >> And then the only way to get the data consistent again, is to (deep)scrub. >> >> Not a very appealing lookout?? >> >> --WjW >> >> >> _______________________________________________ >> ceph-users mailing list >> [email protected] >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >> > > > > -- > Brian Andrus > Cloud Systems Engineer > DreamHost, LLC > -- Brian Andrus Cloud Systems Engineer DreamHost, LLC
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