On Thu, 18 Oct 2007, Andreas Dilger wrote: >> We are doing some testing, >> >> For a OST with a xserve raid connected to linux, is it better to not >> have a partition table >> or to have a partition?
> 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. I found http://insights.oetiker.ch/linux/raidoptimization.html a while ago that discusses the alignment issue. I don't agree with the "Linux Kernel Config Parameters" section, but the rest of the article regarding alignment is OK. The quick summary is: When using raid5/6, use LVM or no partitioning at all. Stay away from PC partition tables. When using hardware raid, use the correct mkfs-parameters to communicate stripe-size info to the FS. /Nikke -- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Niklas Edmundsson, Admin @ {acc,hpc2n}.umu.se | [EMAIL PROTECTED] --------------------------------------------------------------------------- I used to read books. Now I read .qwk files. =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= _______________________________________________ Lustre-discuss mailing list [email protected] https://mail.clusterfs.com/mailman/listinfo/lustre-discuss
