On Fri, Mar 12, 2010 at 1:33 PM, Trond Myklebust <trond.myklebust@xxxxxxxxxx> wrote: > On Fri, 2010-03-12 at 13:22 -0500, Brandon Simmons wrote: >> I am using tiobench to test performance of an NFS mounted volume, and >> notice that Sequential Reads are much slower than Random Reads. This >> isn't the behavior when I run the same test on the disk mounted >> locally. >> >> For random reads I'm getting: >> >> 50 MB/s over NFS >> >> v.s >> >> 384 MB/s when mounted locally >> >> This is in comparison to the benchmark for _Random Reads_, in which I get: >> >> 288 MB/s both over NFS _and_ when directly mounted >> >> The other benchmarks seem to be in line with what I would expect, but >> I'm fairly new to NFS. Why would sequential reads over NFS be sooo >> much slower than random reads over NFS? > > They're not usually. My guess is that this is an artifact of your test. > What is tiobench doing prior to the sequential read? > > Trond > > I'm wondering if this is caused by caching. my benchmark does Sequential Reads first, then it does Random Reads. Is it possible that the random reads could be working on cached data? That would mean my sequential reads aren't too slow, rather the random reads are extraordinarily fast because of caching. Looking at running some different benchmarks. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
