On 04/04/2014 04:16 AM, Alessio wrote: > Hi. > I'm not here to reiterate a discussion. Just for curiosity. > I have a server (Fujitsu Primergy RX300 S8) with a RAID card (LSI > D2607). And 6 SATA disks, 3TB each one. > I cannot configure disks as JBOD, but as usual in this case, I've > created 6 RAID0 volumes. > > I have no way to put zil in an SSD. > I've then tried to configure the zpool in two ways: > - 3 two-way mirrors > - raidz2 > > > If I use a command like this: > dd if=/dev/zero of=prova bs=128k count=10000 > > I get these results (average). > > - mirror > > in the GZ 1734 MB/s > in a zone 382 MB/s > in a KVM 149 MB/s > > - raidz2 > > in the GZ 1597 MB/s > in a zone 302 MB/s > in a KVM 30.8 MB/s > > > 30.8 MB/s is poor! > And why so much difference between zones and GZ?
Well, first off. KVM guests always perform synchronous writes. Therefore, that'll be much more expensive than anything else. For the other differences, I'd seriously go through and do active benchmarking (http://brendangregg.com/activebenchmarking.html). There are many factors that could happen here, but from your numbers, it's almost certain that you're testing asynchronous writes in the case of the GZ and the normal zone as opposed to a KVM instance which is issuing synchronous writes. You could easily be hitting other things such as the I/O throttle, CPU throttling, etc. You'll need to dig into your configuration. Robert ------------------------------------------- smartos-discuss Archives: https://www.listbox.com/member/archive/184463/=now RSS Feed: https://www.listbox.com/member/archive/rss/184463/25769125-55cfbc00 Modify Your Subscription: https://www.listbox.com/member/?member_id=25769125&id_secret=25769125-7688e9fb Powered by Listbox: http://www.listbox.com
