Linked by Thom Holwerda on Sat 18th Nov 2006 18:20 UTC, submitted by bnolsen
Linux "SpadFS is a new filesystem that I design and develop as my PhD thesis. It is an attempt to bring features of advanced filesystems (crash recovery, fast directories) and good performance without increasing code complexity too much. Uses crash counts instead of journaling (because journaling is too complex and bug-prone) and uses hash instead of btrees for directory organization."
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RE[2]: Uhm...
by christian on Tue 21st Nov 2006 16:33 UTC in reply to "RE: Uhm..."
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As in journaling filesystems, some data loss is possible during a crash, but the filesystem is always recoverable. Performance should be better since metadata is only written to disk once.

Journalling generally improves the performance of especially meta-data intensive tasks. This is because the meta-data can not only be written asynchronously, but it is also written contiguously in the journal, and once in the journal, it is to all intents and purposes written to the filesystem and processing can continue.

If, like ext3, data can be journalled as well, this can further improve performance for the same reasons as meta-data.

In a simple test (10000 non-transactioned inserts into a SQLite database):

ext2: 279s
ext3: 297s
ext3 + writeback data: 236s
ext3 + journalled data: 123s
jfs: 366s
xfs: 313s

Here, default ext3 pays the price for ordered data writing, which is a pessimistic writing mode not used by XFS or JFS, which behave more like the writeback data mode of ext3.

I must say, the speed up by using journalled data in ext3 even surprised me! As did the IO overhead of JFS.

All in all, the above quick test shows ext3 in a very good light!

Disclaimer: All tests done using LVM on the same disk, but different LVs. YMMV. All tests are single runs, and not very scientifically done.

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