writer-rbd.py

#!/usr/bin/env python

'''
Simple Python script which endlessly keeps writing 100MB to a temp file.

Used to demonstrate a Ceph cluster. This script runs inside a Virtual Machine (KVM)
running on a RBD image on a Ceph cluster.

The demo is to randomly pull out machines and show that the script can still write
and read data.

Author: Wido den Hollander <wido@42on.com>
'''

import tempfile
import time
import os

# Filesize in MB to write
total_size = 1024

# Write in chunks of 4MB
chunk_size = 4

def main():
    z = open('/dev/zero', 'r')
    i = 0
    while True:
        try:
            start = time.time()
            f = tempfile.NamedTemporaryFile(dir='/tmp', delete=False)
            print "[ %d ] Starting to write %dMB to %s" % (i, total_size, f.name)
            o = 0
            while o < (total_size * 1024 * 1024):
                f.write(z.read(chunk_size * 1024 * 1024))
                f.flush()
                o += chunk_size * 1024 * 1024

            print "[ %d ] Done writing to %s, calling fsync" % (i, f.name)
            os.fsync(f)
            os.unlink(f.name)
            runtime = time.time() - start
            bandwidth = total_size / runtime
            print "[ %d ] Wrote %dMB to %s in %.2f seconds (%.2fMB/sec)" % (i, total_size, f.name, runtime, bandwidth)
            i += 1
        except (KeyboardInterrupt, SystemExit):
            break
   
    z.close()

if  __name__ =='__main__':
    main()