Hello all. For my application, which is written in Java, I need a file system, on top of Linux software raid-0 (md), that guarantees contiguous allocation of blocks for a large number of small files, in order to increase write throughput. For this reason, in the last days I have been experimenting with nilfs2, which seems the best solution for my application needs. I am running Red Hat Enterprise Linux 5 (rhel5), kernel-version 2.6.18-prep, nilfs-2.0.16 and nilfs-utils-2.0.14. Software Raid-0 consists of two Maxtor 500 GB with chuck size 64K. System's Memory is 2GB. For testing reasons I wrote a simple disk benchmark in java, where 8 threads append 256KB dummy blocks from memory to a log-file. Total IO is 8 GB. With ext3 mounted with data=writeback mode, each drive alone gives 63MB/sec and as a raid-0 array a total of 90 MB/sec.
Nilfs has worst performance for the same scenario. 1 Disk alone gives 34MB/sec and two disks on raid-0 setup 39 MB/sec. Using iostat I can see that disks are 50% utilized with nilfs, whereas with ext3 are 100% utilized. Why is this happening? Is my configuration wrong? -- Thanks, G.S.
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