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Will this affect performance? Why 500? And how can I minimize the size of the cache? 2 service less than 500 MB will be faster than one with more that 500MB? Thanks

  • 1
    Why do you think this is going to be a problem? I've seen Multi GB tile caches. – Devdatta Tengshe Feb 11 '14 at 12:08
  • I think that affect performance or not? – SysRq308 Feb 11 '14 at 12:19
  • I'm currently working with a cache subset that's over a terabyte (because I didn't need the other five levels for my prototype). If you review the purpose and implementation of caches, you'll understand that size doesn't matter. – Vince Feb 11 '14 at 13:31
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You name 500MB cache size because of the setting you get when running the caching process after publishing a map service. This is the default setting you get in ArcGIS Desktop which can be seen in ArcMap > Customize > ArcMap Options > Sharing tab. You can disable this warning if you know that you are going to generate multiple caches of bigger size.

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Why 500? Just a fairly big value Esri had in mind :) this setting is useful to warn a novice user that he/she is doing something potentially wrong if his cache will be that big (probably chosen to cache a map document in really large scales while having a big geographic area).

There is no direct correlation between the size of the map service cache and its drawing performance. However, it takes longer time to retrieve bigger tiles (=image files on disk) than to retrieve smaller tiles.

You can make your cache smaller by:

  • choosing a tile format that takes less space by supporting fewer colors (PNG8) or compressing losing quality (JPEG);
  • using compact cache format (multiple files within bundles) instead of exploded (4K cluster size on Windows will be occupied by a file anyway even if its size is just 1K) - particularly relevant for PNG8 files;
  • cache just some often visited areas and/or use caching on-demand (which can potentially result in caching the whole geographic anyway if your users will visit every single extent of your map in every single scale);
  • cache your map just in some scales (most of the tiles are generated in large scales)

And no, 2 services less than 500 MB will not work faster than one with more that 500MB. It is OK to have a map service with large cache size. If the performance of drawing cache is poor than one should try to troubleshoot this by evaluating various phases of cache tiles retrieval such as network capacity, ArcGIS Server machine hardware and OS performance, and number of users accessing the map service.

Please review some help pages on:

Available map cache properties

Strategies for creating map cache tiles

Tips and best practices for map caches

Cached map service in System Design Strategies (Esri)

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