<div dir="ltr"> In testing how to cope with naive users generating millions of tiny files, I noticed some surprising (to me) behavior on a lustre 2.10/ZFS 0.7.0 system.<div><br></div><div> The test directory (based on actual user data) contains about 4 million files (avg size 8.6K) in three subdirectories. Making tar files of each subdirectory gives the total nominal size of 34GB, and using "zfs list", the tar files took up 33GB on disk.</div><div><br></div><div> The initially surprising part is that making copies of the tar files only adds 9GB to the disk usage. I suspect that the creation of the tar files is as a bunch of tiny appendings, and with a raidz2 on ashift=12 disks (4MB max recordsize), there is some overhead/wasted space on each mini-write. The copies of the tar files, however, could be made as a single write that avoided the overhead and probably allowed the lz4 compression to be more efficient. <br clear="all"><div><br></div><div> Are there any tricks or obscure tar options that make archiving millions of tiny files on a Lustre system avoid this? It is not a critical issue, as taking a minute to copy the tar files is simple enough.</div><div><br></div><div>-Nate</div><div><br></div>-- <br><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><pre>Dr. Nathan Crawford <a href="mailto:nathan.crawford@uci.edu" target="_blank">nathan.crawford@uci.edu</a>
Modeling Facility Director
Department of Chemistry
1102 Natural Sciences II Office: 2101 Natural Sciences II
University of California, Irvine Phone: 949-824-4508
Irvine, CA 92697-2025, USA</pre></div></div>
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