Segment size should be 128. 128 KB * 8 data drives = 1 MB.
On 10/19/10 3:42 PM, "Edward Walter" <ewal...@cs.cmu.edu> wrote: > Hello All, > > We're doing a fresh Lustre 1.8.4 install using Sun StorageTek 2540 > arrays for our OST targets. We've configured these as RAID6 with no > spares which means we have the equivalent of 10 data disks and 2 parity > disks in play on each OST. > > We configured the "Segment Size" on these arrays at 512 KB. I believe > this is equivalent to the "chunk size" in the Lustre operations manual > (section 10.1.1). Based on the formulae in the manual: in order to have > my stripe width fall below 1MB; I need to reconfigure my "Segment Size" > like this: > > Segment Size <= 1024KB/(12-2) = 102.4 KB > so 16KB, 32KB or 64KB are optimal values > Does this seem right? > > Do I really need to do this (reinitialize the arrays/volumes) to get my > Segment Size below 1MB? What impact will/won't this have on performance? > > When I format the OST filesystem; I need to provide options for both > stripe and stride. The manual indicates that the units for these values > are 4096-byte (4KB) blocks. Given that, I should use something like: > > -E stride= (one of) > 16KB/4KB = 4 > 32KB/4KB = 8 > 64KB/4KB = 16 > > stripe= (one of) > 16KB*10/4KB = 40 > 32KB*10/4KB = 80 > 64KB*10/4KB = 160 > > so for example I would issue the following: > mkfs.lustre --mountfsoptions="stripe=160" --mkfsoptions="-E stride=16 -m > 1" ... > > Is it better for to opt for the higher values or lower values here? > > Also, does anyone have recommendations for "aligning" the filesystem so > that the fs blocks align with the RAID chunks? We've done things like > this for SSD drives. We'd normally give Lustre the entire RAID device > (without partitions) so this hasn't been an issue in the past. For this > installation though; we're creating multiple volumes (for size/space > reasons) so partitioning is a necessary evil now. > > Thanks for any feedback! > > -Ed Walter > Carnegie Mellon University > _______________________________________________ > Lustre-discuss mailing list > Lustre-discuss@lists.lustre.org > http://lists.lustre.org/mailman/listinfo/lustre-discuss _______________________________________________ Lustre-discuss mailing list Lustre-discuss@lists.lustre.org http://lists.lustre.org/mailman/listinfo/lustre-discuss