Scott Macdonald - Sun Microsystem wrote: > Below is my customers issue. I am stuck on this one. I would appreciate > if someone could help me out on this. Thanks in advance! > > > > ZFS Checksum feature: > > I/O checksum is one of the main ZFS features; however, there is also > block checksum done by Oracle. This is > good when utilizing UFS since it does not do checksums, but with ZFS it > can be a waste of CPU time. > Suggestions have been made to change the Oracle db_block_checksum > parameter to false which may give > Significant performance gain on ZFS. > > What are Sun's stance and/or suggestions on making this change on the > ZFS side as well as making the changes on the Oracle side. > >
I don't think it is appropriate for Sun to take a stance. Data integrity is more important than performance for many people, so let them decide to make that trade-off. It should be noted that for performance benchmarking, it is not uncommon for checksums to be disabled, since it is a competitive environment where performance is all that matters. That isn't the real world. In the ZFS case, a checksum mismatch for a redundant configuration will result in an attempt to correct the data. In other words, the checksum is an integral part of the redundancy check. Disabling the checksum will mean that only I/O errors are corrected -- a subset of the possible problems. This plays into the overall risk structure of the system implementation because not only do you have to worry about faults, but now you have to worry about propagation paths for the faults through at least 3 major pieces of software. The trade-off is not simply a data corruption, but also isolation of data corruption. This is not the typical level of analysis I see in our customer base. -- richard _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
