Some times ago I bought a STEC ZeusIOPS SSD with 18GB capacity. This disks comes out from a Sun ZFS Storage 7420 system. But it’s 3.5″ large and without a server which supports 3.5″ large SAS disk drives I couldn’t test the SSD. Today I was able to test the drive on a Fujitsu Primergy RX300 S5 server. I installed five 500 GB large SATA drives and my STEC ZeusIOPS SSD. The first disk contains an OpenIndiana installation, the rpool. The remaing four SATA drives are grouped as a ZFS RAIDZ2 pool. I exported a ZFS dataset over NFS and 1 GbE to a VMware ESX system. With a Ubuntu linux virtual machine I run several benchmarks.
The results without the SSD are 75-80 MBytes/s write (850ms latency), between 40 and 65 MBytes/s rewrite and 120 MBytes/s read performance. I did different runs with bonnie++ and iozone and achieved always similar values. During the tools did their benchmarks I watched the IO with “zfs iostat”. The write and rewrite results matched the numbers above. Reading lot’s of data from disk was not necessarry due a large enough ARC mem cache. That’s why the iostat output values was lower than 10 Mybtes/s.
Then I added the STEC SSD as log device to the ZFS pool and rerun all the tests. But I couldn’t believe the values!!! My benchmarks finished with only 45-50 MBytes/s write and 35-45 MBytes/s rewrite. Read performance didn’t changed, of course. The write latency exceeded 10000ms!!! Something went wrong but I don’t know what. I did the runs again and I watched the zfs iostat output parallel. But the output of zfs iostat throwed values always above 100 Mbytes/s. Sometimes I reached even values above 170 MBytes/s, but always more than 100 Mbytes/s. This is the maximum rate for a single 1 GbE connection! But the benchmark output was very different. They didn’t reached the results of the benchmark without the SSD. I was confused. I disabled the log device with the logbias option and set it to throughput. The benchmark result and the iostat results went back to 75-80 Mbytes/s write. I reenabled the log device with logbias=latency and I had again the benchmark result of max. 50 Mybtes/s write and big latency values but with an iostat ouput always over 100 Mbytes/s!
Something is wrong, but I don’t know what. 
Do you have an idea?
And one is very exciting ! I started to rethink and rebuild my HP blade environment. Yesterday a new toy arrived. Have a look at the backside of my HP c-Class BladeSystem. You can see a very important interconnect module for a Converged Infrastructure. 
That’s absolutely great! I love that new toy… 
) mit je 14 Stück 146 GB Fibre Channel Festplatten hat? Eigentlich klar, die Arrays konfigurieren und an das SAN klemmen. Tja, was ist aber wenn die installierten RAID Controller einfach nur grausam in der Bedienung sind, man maximal 2 Volumes pro Disk Array erstellen kann und die Geschwindigkeit mit ZFS einfach nur lausig ist?
