[Samba] Re: File Systems - Which one to use?

Dragan Krnic dkrnic at t-online.de
Sat Dec 21 08:21:02 GMT 2002

With reference to my earlier posting in this thread (Dec 16, 2002),
where I quoted some timings for tar and dump on ext and reiserfs,
I received a mail from Mr. Stelian Pop, the maintainer of BSD/dump,
who noted that tar is actually cheating when outputting to the bit
bucket. I've checked it up and found out that tar indeed skips a
lot if the target ("-f") is either "/dev/null" or redirected to
"/dev/null". My suspicion that there is something wrong with IPC
in Linux was unwarranted. The reason why tar is so much slower
when it writes through a dd pipe is that it then needs to output
all the data without skipping anything. To better understand the
issue look at this table of backup speeds (in MB/s) and ratios:

                         ext3     reiserfs       ratio
Backup method\From   (fastdisk)  (slowdisk)   reiserfs/ext3
------------------   ----------  ----------   -------------
      tar > null         23.5        66.7         2.84
     dump > null         19.4         --           ?

       dd > null         32.2        23.4          .73

 tar | dd > null         10.3         8.8          .85
dump | dd > null         18.7         --           ?

It shows that dump is a quite a bit more efficient backup tool
than tar when tar doesn't cheat. A tar from ext3 is some 15%
slower than a dump if we factor in the relative speeds of the
two disks. That it is 2.8 times faster on reiserfs than on ext3
when it basically skips all data and only traverses the directories
proves my point from previous postings - reiserfs is a quite a lot
more responsive file system for meta data manipulations than ext3.
Seeing how much handshake and massaging of meta data is caused
by SMB I am prone to believe that reiserfs is ideal fs for samba.

I hope to be able to fill in the blanks under dump/reiser entries
in about a month and a half and then we shall review the data.
My prediction is that a good reiserdump would be streaming at 
about 35 MB/s or better on the faster of the two IDE disks.

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