Performance issue on ASM disk group.

Hi.

    Stand on the platform OEL 6.6 x86_64. GI/DB version 11.2.0.4. Installed according to the documentation. For database files using 4 WDRed drive of 3 TB. Each is divided into two partitions of 1.5 TB (1,500,000 MB). From these eight partitions created ASM disks and gathered a group DATA (external). The group works very very slowly. For example, I stopped instance of the database and copied from the asmcmd data file to /tmp (just single drive). Result: Each ASM disk spend is only 10 MB for read. Recording into /tmp goes about 127-130 MB/sec.

    I create another stand with the same characteristics, but without ASM. Datafiles placed in the file system (ext4). If I attempt to add a datafile into some tablespace, second stand spends almost three times less time. Not the first time dealing with ASM. With this case in the first meeting. The dd command indicates that the entry in the partition is at a speed of 250 MB/sec. No errors/warnings in +ASM_alert/messages/db_alert. Any advices?