Yannis Klonatos wrote: > Hi all! > > I have come across the following peculiar behavior in XFS and i > would appreciate any information anyone > could provide. > In our lab we have a system that has twelve 500GByte hard disks > (total capacity 6TByte), connected to an > Areca (ARC-1680D-IX-12) SAS storage controller. The disks are configured > as a RAID-0 device. Then I create > a clean XFS filesystem on top of the raid volume, using the whole > capacity. We use this test-setup to measure > performance improvement for a TPC-H experiment. We copy the database > over the clean XFS filesystem using the > cp utility. The database used in our experiments is 56GBytes in size > (data + indices). > The problem is that i have noticed that XFS may - not all times > - split a table over a large disk distance. For > example in one run i have noticed that a file of 13GByte is split over a > 4,7TByte distance (I calculate this distance > by subtracting the final block used for the file with the first one. The > two disk blocks values are acquired using the > FIBMAP ioctl). xfs_bmap output would be a lot nicer. Maybe you can paste that here to show exactly what the layout is. -Eric > Is there some reasoning behind this (peculiar) behavior? I would > expect that since the underlying storage is so > large, and the dataset is so small, XFS would try to minimize disk seeks > and thus place the file sequentially in disk. > Furthermore, I understand that there may be some blocks left unused by > XFS between subsequent file blocks used > in order to handle any write appends that may come afterward. But i > wouldn't expect such a large splitting of a single > file. > Any help? > > Thanks in advance, > Yannis Klonatos _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
