On Sun, Oct 18, 2009 at 8:37 PM, Jon Burgess <jburgess777@xxxxxxxxxxxxxx> wrote: > On Sun, 2009-10-18 at 18:44 +0530, Viji V Nair wrote: >> On Sun, Oct 18, 2009 at 5:11 PM, Matija Nalis <mnalis-ml@xxxxxxxxxx> wrote: >> > On Sun, Oct 18, 2009 at 03:01:46PM +0530, Viji V Nair wrote: >> >> The application which we are using are modified versions of mapnik and >> >> tilecache, these are single threaded so we are running 4 process at a >> > >> > How does it scale if you reduce the number or processes - especially if you >> > run just one of those ? As this is just a single disk, 4 simultaneous >> > readers/writers would probably *totally* kill it with seeks. >> > >> > I suspect it might even run faster with just 1 process then with 4 of >> > them... >> >> with one process it is giving me 6 seconds > > That seems a little slow. Have you looked in optimising your mapnik > setup? The mapnik-users list or IRC channel is a good place to ask[1]. > > For comparison, the OpenStreetMap tile server typically renders a 8x8 > block of 64 tiles in about 1 second, although the time varies greatly > depending on the amount of data within the tiles. > >> > >> >> time. We can say only four images are created at a single point of >> >> time. Some times a single image is taking around 20 sec to create. I >> > >> > is that 20 secs just the write time for an precomputed file of 10k ? >> > Or does it also include reading and processing and writing ? >> >> this include processing and writing >> >> > >> >> can see lots of system resources are free, memory, processors etc >> >> (these are 4G, 2 x 5420 XEON) > > 4GB may be a little small. Have you checked whether the IO reading your > data sources is the bottleneck? I will be upgrading the RAM, but I didn't see any swap usage while running this applications... the data source is on a different machine, postgres+postgis. I have checked the IO, looks fine. It is a 50G DB running on 16GB dual xeon box > >> > If you can modify hardware setup, RAID10 (better with many smaller disks >> > than with fewer bigger ones) should help *very* much. Flash-disk-thingies of >> > appropriate size are even better option (as the seek issues are few orders >> > of magnitude smaller problem). Also probably more RAM (unless you full >> > dataset is much smaller than 2 GB, which I doubt). >> > >> > On the other hand, have you tried testing some other filesystems ? >> > I've had much better performance with lots of small files of XFS (but that >> > was on big RAID5, so YMMV), for example. >> > >> > -- >> > Opinions above are GNU-copylefted. >> > >> >> I have not tried XFS, but tried reiserfs. I could not see a large >> difference when compared with mkfs.ext4 -T small. I could see that >> reiser is giving better performance on overwrite, not on new writes. >> some times we overwrite existing image with new ones. >> >> Now the total files are 50Million, soon (with in an year) it will grow >> to 1 Billion. I know that we should move ahead with the hardware >> upgrades, also files system access is a large concern for us. There >> images are accessed over the internet and expecting a 100 million >> visits every month. For each user we need to transfer at least 3Mb of >> data. > > Serving 3MB is about 1000 tiles. This is a total of 100M * 1000 = 1e11 > tiles/month or about 40,000 requests per second. If every request needed > an IO from a hard disk managing 100 IOPs then you would need about 400 > disks. Having a decent amount of RAM should dramatically cut the number > of request reaching the disks. Alternatively you might be able to do > this all with just a few SSDs. The Intel X25-E is rated at >35,000 IOPs > for random 4kB reads[2]. > > I can give you some performance numbers about the OSM server for > comparision: At last count the OSM tile server had 568M tiles cached > using about 500GB of disk space[3]. The hardware is described on the > wiki[4]. It regularly serves 500+ tiles per second @ 50Mbps[5]. This is > about 40 million HTTP requests per day and several TB of traffic per > month. > > Jon > > > 1: http://trac.mapnik.org/ > 2: http://download.intel.com/design/flash/nand/extreme/extreme-sata-ssd-product-brief.pdf > 3: http://wiki.openstreetmap.org/wiki/Tile_Disk_Usage > 4: http://wiki.openstreetmap.org/wiki/Servers/yevaud > 5: http://munin.openstreetmap.org/openstreetmap/yevaud.openstreetmap.html > > > I have to give a try on mod_tile. Do you have any suggestion on using nginx/varnish as a cahce layer? -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
