Emoly_Liu_Qian_Yingjin_Xfast_Extreme_File_Attribute_Stat_Acceleration_for_Lustre.pdf

1、Xfast:Extreme File Attribute Stat Acceleration for LustreQian Yingjin,Liu Y,Nov.3rd,OutlineBackground and motivationXfast design and implementation Scalable statahead Batch RPC engine Subtree aggregate statahead(SAS)Size on MDT(SoM)Scale-out stathead Thrashing avoidancePerformance evaluationConclusi

2、on and future Background and MotivationData is growing at an extreme pace 10,000,000+files in a singe directoryMany HPC applications suffer most from slow directory scans Directory tree walks cost much time(minutes to hours)How to improve directory tree walks performanceFile Attribute StatAttribute

3、fetching and cachingin LustrePrefetchAggregatePFile Attribute StatSerialized POSIX interface Retrieval only operate on a single directory entry at a time;The traversal of a directory with millions of entries can take tens of minutes to complete due to repetitive stat()calls.Use predictable access pa

4、tterns to prefetch metadata.POSIX semantics Need to return the most recent file information when listing directories;New statx()system call allows applications to request specific attributes to minimize unnecessary overhead.Reduce the number of RPC calls per statx()operation and allowed us to implem

5、ent lazy and strict Size on MDT-feature(SoM)for Lustre.Parallel prefetching of attributes mpiFileUtils+dfind,drm,dcp,Convert the serial stat()access from user process into parallel asynchronous Attribute Fetching and Caching in Lustrestat()path in Lustre1.An RPC is sent to the MDT to acquire a lock;

6、2.MDT returns a protected read(PR)lock,along with metadata attributes and layout extended attribute(EA);3.Send a glimpse PR lock request with the extent range 0,EOF to OSTs to obtain the current file size and blocks attributes.Distributed lock manager(DLM)Protect data and metadata consistency;If a c