ss77892 commented on PR #9947:
URL: https://github.com/apache/ozone/pull/9947#issuecomment-4193416940

   >@ss77892 In RO/Secondary mode, the SST files are opened and their metadata 
is checked. Each SST file's footer, metaindex blocks, properties block are 
read. No data related checks are performed though. So integrity and correctness 
of the SST files is partially present but not for the main contents of the SST 
file.
   It seems that this statement is not correct. I just checked the open RO with 
strace, and it doesn't touch sst files at all:
   ```
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/CURRENT",
 O_RDONLY|O_CLOEXEC) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db",
 O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/CURRENT",
 O_RDONLY|O_CLOEXEC) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/MANIFEST-001732",
 O_RDONLY|O_CLOEXEC) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db",
 O_RDONLY|O_DIRECTORY) = 15
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/IDENTITY",
 O_RDONLY|O_CLOEXEC) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db",
 O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db",
 O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/CURRENT",
 O_RDONLY|O_CLOEXEC) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/MANIFEST-001732",
 O_RDONLY|O_CLOEXEC) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db",
 O_RDONLY|O_DIRECTORY) = 15
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/IDENTITY",
 O_RDONLY|O_CLOEXEC) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db",
 O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/001731.log",
 O_RDONLY|O_CLOEXEC) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/001735.log",
 O_RDONLY|O_CLOEXEC) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/001737.log",
 O_RDONLY|O_CLOEXEC) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/001739.log",
 O_RDONLY|O_CLOEXEC) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/001742.log",
 O_RDONLY|O_CLOEXEC) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/001744.log",
 O_RDONLY|O_CLOEXEC) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/001746.log",
 O_RDONLY|O_CLOEXEC) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/001748.log",
 O_RDONLY|O_CLOEXEC) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/001751.log",
 O_RDONLY|O_CLOEXEC) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/001753.log",
 O_RDONLY|O_CLOEXEC) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/001755.log",
 O_RDONLY|O_CLOEXEC) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/001758.log",
 O_RDONLY|O_CLOEXEC) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/001760.log",
 O_RDONLY|O_CLOEXEC) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/001762.log",
 O_RDONLY|O_CLOEXEC) = 13
   [pid 1992410] openat(AT_FDCWD, 
"/home/ssa/rocks/12/hdds/rocksdb-sim-cluster/DS-187f5526-f62d-43a6-8436-f8e7e625e6ea/container.db/001764.log",
 O_RDONLY|O_CLOEXEC) = 13
   ```
   So, opening it RO looks quite useless because it reads the metadata and logs 
only, and wastes CPU reading log files into the memory. 


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