Using dd is not a got way to evaluate performances. dd does sequential serialized I/Os, and this is the worst case scenario for vdisk. With real applications, most your disk I/Os will be multiple parallel random I/Os (done by the filesystem) so this is definitively not what dd is testing.
A better way to test I/Os is to use vdbench, with which you can simulate different type of workload. But the best test is to run your applications, and see how it behaves and if you have unexpected response time. alex. On 06/10/10 03:01, Tom Kuther wrote:
We have seen the same problem on a T5220, LDOMs 1.3, 8 internal 10k SAS drives and ZFS all around. Even on the ZFS RAID1 ldompool inside the control domain, I couldn't get over 46MB/s with dd testing. Same for the 6-disk RAIDz inside the guest LDOM (exported slice 2 of EFI labeled disk, formed into RAIDZ) I deleted all LDOM configs and rebooted factory-default, same tests reveal around 100MB/s on the same ldompool now, and about 90MB/s for the RAIDZ, So now we end up using zones instead. (Originally posted on sun forums: http://forums.sun.com/thread.jspa?threadID=5441479)
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