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Sequential write and read tests are meaningful when writing or reading large amounts of data on a relatively empty disk. Once the disk fills up, or if the application involves reading from different parts of a database, then random read and write tests become more important.
Results are much slower for random read and write tests. That's not surprising considering that disk heads move around a lot more in a random test than they would with sequential operations. Here, the larger 64-kbyte records help, since there's more time spent writing or reading relative to disk seek time. Still, both 4- and 64-kbyte read and write times are just a fraction of the sequential times.
In the worst case, writes of 4-kbyte records are just 3MBps, compared with 276MBps with sequential writes. In fairness, though, any storage systems would do far worse in random tests than in sequential ones. These results aren't a reflection on FreeNAS or ZFS.
Overall, FreeNAS offers a very positive story, with flexibility, ease of management, good performance - and a price that can't be beat.
Thanks to Arista Networks for supplying a 7124S 10G top-of-rack switch that tied together all systems on the test bed.
Newman is a member of the Network World Lab Alliance and president of Network Test, an independent test lab and engineering services consultancy. He can be reached at email@example.com.
How We Did It
We assessed FreeNAS in terms of usability, features, and NFS I/O performance. In performance tests, the device under test was an iX-2212 server supplied by iXsystems; as part of usability testing, we also installed the FreeNAS software on an older SuperMicro server and as a virtual machine running under VMware vSphere 5. We used FreeNAS version 8.3.0-RELEASE-x64 (r12701M) in testing.
Usability and features testing consisted of setting up the device to function as an NFS server, and then again as an iSCSI network-attached storage (NAS) device. In the NAS case, we created FreeBSD virtual machines using VMware vSphere 5 on VMware ESX 5.0 hosts, and used FreeNAS as the datastore.
We also assessed FreeNAS's ability to conduct other common management tasks, such as configuration of administrator rights; software upgrades; and setup of link aggregation groups using two 10G Ethernet interfaces.
For NFS I/O performance testing, we used iozone, an open-source file system benchmarking tool. The goal of these I/O tests was to compare client performance under six common scenarios: initial sequential writes; sequential rewrites; initial sequential reads; sequential rereads; and random reads and writes. Each of two NFS client machines ran FreeBSD 8.3 and ran iozone with file sizes of 32GB and eight threads apiece, for a total of 64GB and 16 threads per test. We repeated the iozone tests with 4- and 64-kbyte record sizes.
To get a sense of combined disk I/O and caching performance, we deliberately constrained both the FreeNAS server and the client machines to use 6GB of RAM, much less than the hardware RAM installed in server or clients. This forced a larger number of disk I/O operations in testing, as might be the case with larger numbers of users and/or files in enterprise settings.