To help dispell some boredom tonight and satisfy some of my curiosity... I did a little impromptu benchmarking with the new ext4 filesystem as delivered in the 2.6.19 kernel.
What I did, was pop a 256meg cfdisk into my laptop and did a few file operations on it via a simple script that formatted the card, mounted it and then copied 256meg of data onto it in various fashions... I compare ext2, ext3 and ext4dev. The ext4dev was tested both with and without extents enabled, to get a basic feel for the differences. I then did a test to see just how backward compatible ext4dev is to ext3 and ext2... All three file systems were mounted with the sync flag enabled to eliminate any delay of actually writing the data to the cf card and ended with a sync before ending the timing loop for good measure. Anyways... I got some really interesting results which all boils down to this. The ext2 test run took so damn long that I manually terminated the test after 10minutes... Ext3 took about 6minutes to complete, ext4dev with extents took 4 minutes, ext4dev without extents took about 5. The same numbers came up, again and again during three complete runs of the test script. The ext2 fs was formatted with "mke2fs" and mounted with "-t ext2 -o sync" The ext3 fs was formatted with "mke2fs -j" and mounted with "-t ext3 -o sync" The ext4 fs was formatted with "mke2fs -j" and mounted with "-t ext4dev -o sync" The ext4 fs was formatted with "mke2fs -j" and mounted with "-t ext4dev -o sync,extents" Results: ext2 - never completed... I got too tired waiting for it to eor. ext3 - 6 minutes. ext4 - 5 minutes no extents ext4 - 4 minutes with extents Then... after running the ext4dev with extents test, I unmounted the cf card and tried mounting it with ext2, ext3 and ext4dev (no extents), failing all three times. Once you write to an ext4 file system using the extents option, it ext4 forever... After reformatting the card, mounted with ext4dev (no extents option) and did some simple writes to the card (no extents), I then ran my mount tests again... ext2, ext3 and ext4dev (with extents) and it succeeded all three times. >From my humble tests, I conclude the following: The ext4dev filesystem has some serious performance offerings for those of us that use ext3. Also, as long as you don't write to an ext4dev filesystem mounted with the extents option, it'll be as backwards compatible to ext3 and ext2, just as ext3 is currently to ext2. That is to say, if you don't use ext4 extents for the added performance benefits, you'll have the option open to you to back level to ext3 with out problems or even back to ext2. NOTE: When changing filesystems in such a manner on a partition with valuable data, besure to backup before making the change and running fsck on it before actually using it... Wow... Let the real testing begin. For my workhorse test box, I'm going to convert a document server to ext4dev tomorrow. The server is a little used, heavily backed up box, sporting about 600gid worth of some of the most boring stuff you have ever read. It'll be interesting to see just how it behaves in "the wild". >From the little testing I've done, I'm quite impressed with the first public exposure to a developing filesystem. I can't imagine how things will progress with ext4, but based on these early developments... it's going to be good. Cheers all... hmmm... I'm finally sleepy enough to get some sleep. :'O -- Jerry McBride -- gentoo-user@gentoo.org mailing list
