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? > > 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 -- 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
