Originally posted by: Stephan B.
Hello everybody,
I have a performance problem which is driving me insane. Situation: 2 x RAID5 arrays connected to the local scsi adapter, 3 x RAID5 arrays on a direct attached DS3400 (2 GB/s HBAs). Each of this hdisks has a reasonable throughput (simple LV on a single hdisk). But even though it's reasonable, it's not sufficient for our purposes, so I created striped LVs and assumed this would double / triple the throughput of sequential writing (tested with dd if=/dev/zero of=/dev/rstripedlv bs=<tried several values>).
But to my surprise the performance was the same as it was when writing to a single hdisk without striping! First I thought there may be a problem with the DS3400 but then I saw the same strange behaviour with the local disks! With iometer I can see that the load is spread equally over the hdisks but the values are only a fraction of the ones I got when writing to a single hdisk (roughly 1/3 with 3 hdisk, 1/2 with 2 hdisks).
Do you have any idea what could be wrong?
Thanks in advance for every hint!
kind regards,
Stephan
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