-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 08/19/2015 05:56 PM, Paolo Bolzoni wrote: > I left running the pragma quick check during the night and finished > in 2 hours and 46 minutes, so it is about 8 times slower than in > ext4. Zfs is an advanced filesystem plenty of features, but this > speed difference is too much I think.
I use btrfs which like zfs is also a copy on write filesystem. It is possible for the files to get very fragmented which can result in dismal performance, even on an SSD even for reads. Random small writes especially aggravate this. btrfs has an autodefrag option that addresses this in the background, and SQLite is specifically mentioned as all the browsers use it behind the scenes as do many email clients. https://btrfs.wiki.kernel.org/index.php/Gotchas (2nd last section) The filefrag command may be helpful if implemented for zfs and will tell you if fragmentation is a problem. Virtual machine images are another problematic file type with similar read/write patterns to SQLite. Copy on write filesystems don't modify existing (meta)data, but rather write new versions that point to the existing data for bits that aren't changed. Repeat this many times and the chains of pointers get very long, which is the fragmentation. Roger -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAlXadDsACgkQmOOfHg372QRdpACfRUmHD4hXfAx6+il0q/7lINxd 9lwAoNAyYV1oa5cYcn1O00JxW4nsI/Sp =VrTq -----END PGP SIGNATURE-----
