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Hi Lukasz, Here's a bit higher of a level of debug: 110127 16:57:13 001 Xrd: Read: Read(offs=2664306755, len=104) 110127 16:57:13 001 Xrd: Read: Cache response: got 104@2664306859 bytes. Holes= 0 Outstanding= 0 110127 16:57:13 001 Xrd: Read: Found data in cache. len=104 offset=2664306755 110127 16:57:13 001 Xrd: Read: Read(offs=2664371953, len=1149) 110127 16:57:13 001 Xrd: Read: Cache response: got 0@2664371953 bytes. Holes= 1 Outstanding= 0 110127 16:57:13 001 Xrd: Read: Hole in the cache: offs=2664371953, len=1149 110127 16:57:13 001 Xrd: Read_Async: Requesting to read 16384 bytes of data at offset 2664366080 110127 16:57:13 001 Xrd: Read_Async: Requesting pathid 0 110127 16:57:13 001 Xrd: Read: Waiting 1outstanding blocks. 110127 16:57:13 16248 Xrd: ProcessUnsolicitedMsg: Incoming unsolicited response from streamid 3 110127 16:57:13 16248 Xrd: ProcessUnsolicitedMsg: Processing async response from streamid 3 father=2 110127 16:57:13 16248 Xrd: ProcessUnsolicitedMsg: Putting kXR_read data into cache. Offset=2664366080 len 16384 This is the URL used: root://xrootd.unl.edu//store/data/Run2010B/BTau/AOD/Dec4ReReco_v1/0007/B26C2B64-E101-E011-9C89-002481E14F38.root?readaheadsz=32768&cachesz=3276800&readaheadstrategy=1&readtrimblksz=16384 So, it seems readtrimblksz works and cachesz/readaheadsz doesn't. Brian On Jan 27, 2011, at 10:46 AM, Lukasz Janyst wrote: > Hi Brian, > > it looks like there are two possibilities: > > * if you're not using a ttreecache: you have disabled the readahead by > configuring an unknown readahead strategy in the environment > * if you're reading from a ttree through a ttreecache: the readahead is disabled > > Cheers, > Lukasz > > On Thu, Jan 27, 2011 at 4:20 PM, Brian Bockelman <[log in to unmask]> wrote: >> Hi, >> >> I'm opening a file with the following opaque data: >> >> root://xrootd.unl.edu:1094//store/data/Run2010B/BTau/AOD/Dec4ReReco_v1/0007/B26C2B64-E101-E011-9C89-002481E14F38.root?readaheadsz=32768&cachesz=327680 >> >> I.e., I would expect the minimal read size is 32KB. However, I see the following read pattern: >> >> 110127 16:11:34 001 Xrd: Read: Hole in the cache: offs=2673920000, len=55 >> 110127 16:11:34 001 Xrd: Read: Hole in the cache: offs=2673920512, len=145 >> 110127 16:11:34 001 Xrd: Read: Hole in the cache: offs=2673921024, len=70 >> 110127 16:11:34 001 Xrd: Read: Hole in the cache: offs=2673921536, len=154 >> 110127 16:11:34 001 Xrd: Read: Hole in the cache: offs=2673922048, len=24 >> 110127 16:11:35 001 Xrd: Read: Hole in the cache: offs=2673922560, len=162 >> >> I would have expected all these reads to be handled by the cache. This is with ROOT 5.27.06b. >> >> Brian >> >>