On 10/19/2014 12:10 PM, Peter Grandi wrote: >>> I am using xfs on a raid 5 (~100TB) and put log on external >>> ssd device, the mount information is: /dev/sdc on >>> /data/fhgfs/fhgfs_storage type xfs >>> (rw,relatime,attr2,delaylog,logdev=/dev/sdb1,sunit=512,swidth=15872,noquota). >>> when doing only reading / only writing , the speed is very >>> fast(~1.5G), but when do both the speed is very slow (100M), >>> and high r_await(160) and w_await(200000). > >> What are your kernel version, mount options and xfs_info output ? > > Those are usually important details, but in this case the > information that matters is already present. > > There is a ratio of 31 (thirty one) between 'swidth' and 'sunit' > and assuming that this reflects the geometry of the RAID5 set > and given commonly available disk sizes it can be guessed that > with amazing "bravery" someone has configured a RAID5 out of 32 > (thirty two) high capacity/low IOPS 3TB drives, or something > similar. > > It is even "braver" than that: if the device name > "/data/fhgfs/fhgfs_storage" is dedscriptive, this "brave" > RAID5 set is supposed to hold the object storage layer of a > BeeFS highly parallel filesystem, and therefore will likely > have mostly-random accesses. > Where do you get the assumption from that FhGFS/BeeGFS is going to do random reads/writes or the application of top of it is going to do that? Bernd _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
