On Oct 18, 2007 13:02 -0400, Brock Palen wrote: > On Oct 18, 2007, at 4:42 AM, Andreas Dilger wrote: > >For RAID 5/6 devices we recommend NOT having a partition table. > >The reason > >is that the partition table offsets the data partitions by a small > >amount > >(512 bytes usually) and this causes writes to span multiple RAID > >chunks and > >unnecessary read-modify-write activity. > > > >For best performance, pick a RAID chunk size that divides evenly into > >1MB (e.g. 4 or 8 data disks + parity). The ldiskfs mballoc code works > >to align the allocation with the RAID chunk size for best performance. > > Thanks I will keep this in mind. > > I did some basics test, 1MDS 1OST 1raid5 (half a xserve raid) Using > tiobench on 1 client, using no partition table netted about 5MB/s > faster for streaming read/write. I will scale up my tests though and > try some other raid configurations. Thanks for the help.
The other important note - don't use RAID5 for the MDS if at all possible. It generates largely small, random 4kB IO and is much better served by RAID1 or RAID1+0. Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc. _______________________________________________ Lustre-discuss mailing list [email protected] https://mail.clusterfs.com/mailman/listinfo/lustre-discuss
