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Running ZFS Natively On Linux Slower Than Btrfs
An anonymous reader writes "It's been known that ZFS is coming to Linux in the form of a native kernel module done by the Lawrence Livermore National Laboratory and KQ Infotech. The ZFS module is still in closed testing on KQ infotech's side (but LLNL's ZFS code is publicly available), and now Phoronix has tried out the ZFS file-system on Linux and carried out some tests. ZFS on Linux via this native module is much faster than using ZFS-FUSE, but the Solaris file-system in most areas is not nearly as fast as EXT4, Btrfs, or XFS."
Which of the ZFS features most impact its performance?
Compression enabled by default can't help (available in btrfs).
Checksum for all blocks probably doesn't help, but definitely helps detect corrupt data/corruption (available in btrfs).
Forcing any file that requires more than a single block to use a tree of block pointers probably doesn't help. The dnode only has one block pointer and the block pointer can only point to a single block (no extents). On the plus side, the block size can vary between 512 bytes and 64 KiB per object, so slack space is kept low. If more than a single block is necessary it creates a tree of block pointers. Each block pointer is 128 bytes in size, so the tree can get deep fairly quick.
Three copies of almost all file system structures (such as inodes, but called dnodes in ZFS) by default can't help (which are compressed of course).
zpool status
That's the command you are looking for. The zfs-fuse lists disks by id which means if you go into /dev/disks/by-id/ and do a ls -al you'll see which devices they are linked to.
It is done this way to make it easier in Linux, in BSD/Solaris the disks are by gpt name (well they were for me) so this keeps it sane.
Hope it helps.
Maq