(I'm adding back the list) On Tue, Feb 02, 2021 at 02:38:41PM -0500, przemek klosowski wrote: > > On 2/1/21 3:34 PM, Richard W.M. Jones wrote > >RAM disks! > > > > # nbdkit memory 10G > > # nbd-client -b 512 localhost /dev/nbd0 > > > Cool! I didn't know about this... the standard way I knew was via tmpfs > > mount -t tmpfs -o size=10g myrd /tmp/ramdisk > > How does it compare to nbd? tmpfs doesn't make a RAM disk block device, instead each file is stored in memory as required. Linux has an actual RAM disk block device, but that's also different from nbdkit-memory-plugin. nbdkit-memory-plugin runs in userspace and implements a sparsely allocated RAM disk. So you can do this on a laptop from 2021 (not 2121 or whenever it will be that we have laptops with 8 exabytes of RAM): # nbdkit memory $(( 2**63 - 1 )) # nbd-client -b 512 localhost /dev/nbd0 # mkfs.btrfs -K /dev/nbd0 The longer answer to this is my talk at FOSDEM: https://archive.fosdem.org/2019/schedule/event/nbdkit/ "Better loop mounts with NBD: Take your loop mounts to the next level with nbdkit". > BTW, I kind-of like using loop devices, because they are persistent > > dd if=/dev/zero of=/tmp/disk bs=1G count=10; mount -o loop > /tmp/disk /mnt/disk1 > > Are you preferring ramdisks because of speed, or is there something else? RAM disks are temporary by their nature. I was suggesting this only as a way to test the hash algos in btrfs. nbdkit has many other plugins customized to different use cases, including many with persistent backing; or you can write your own. https://libguestfs.org/nbdkit.1.html Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-builder quickly builds VMs from scratch http://libguestfs.org/virt-builder.1.html _______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx
