Curious instance here, but perhaps this is the expected behaviour: mount | grep btrfs /dev/sdb3 on / type btrfs (rw,ssd,subvol=@) /dev/sdb3 on /home type btrfs (rw,ssd,subvol=@home) /dev/sde1 on /media/gwb09/btrfs-32G-MicroSDc type btrfs (rw,nosuid,nodev,uhelper=udisks2)
This is on an Ubuntu 14 client. /dev/sdb is indeed an ssd, a Samsung 850 EVO 500Gig, where Ubuntu runs on btrfs root. It appears btrfs did indeed auto detected an ssd drive. However: /dev/sde is a micro SD card (32Gig Samsung) sitting in a USB 3 card reader, inserted into a USB 3 card slot. But ssh is not detected. So is that the expected behavior? If not, does it make a difference? Would it be best to mount an sd card with ssd_spread? The wiki suggests this, but I thought I would check: https://btrfs.wiki.kernel.org/index.php/Manpage/btrfs(5)#MOUNT_OPTIONS I think this is an older btrfs userland tools bundle: btrfs --version Btrfs v3.12 It's whatever is still in the Ubuntu 14 standard (universal?) repository. Here's the tl/dr. This is incidental info, and probably does not affect the question above, or answer. I use btrfs on Ubuntu root, and then zfs for home (lots of data, just shy of 2 TB on this laptop). I snapshot and send the zfs filesystems onto a btrfs formatted sd card, and then use zfs receive for the backup zpools: sudo zfs send -D -v -i 20180830042620u zpb9/home2@20180904005531u > zfs-send-zpb9-home2-20180904005531u (on the sd card, copy to the back up zpools, and then:) zfs receive -v zpf3/BackUpPoolHome < zfs-send-zpb9-home2-20180904005531u No complaints at all about btrfs for the root file system, and apt-btrfs-snapshot works great for rolling back from failed upgrades. My servers are Solaris and Ubuntu, both of which support zfs, as long as I don't upgrade beyond the "dreaded" point of no return for "open source", zpool version 28 and zfs version 5. When one server is upgraded to Ubuntu 18, I will try again to use btrfs on the larger Toshiba Hard Drives (6TB and 8TB, either the x300 NAS or Desktop models). I don't want to try that with Ubuntu 14 given the older userland tools. Many thanks. Please point me to the correct mail list if this is not the right one. Yet another side note: both btrfs and zfs are now "housed" at Oracle (and most of java, correct?). Any chance of Solaris 11 getting btrfs in the kernel? I'm guessing not for Sparc, but it might help x86 Solaris users migrate to Oracle Linux. At this point, I think Ubuntu is the only distribution with a version of both btrfs and zfs in the kernel. But not Oracle. Gordon Bynum
