DragonFly BSD

Setting up swapcache

This page was created from my notes of setting up my SSD as a swapcache. I used the Intel 40 GB X25-V SATA II MLC.

  1. Setting up swapcache
  2. Formatting new drive for swap
  3. Adding Disk to fstab
  4. Setting swapcache to start on boot
  5. Activating the swapcache

Formatting new drive for swap

After you install your drive you should be able to find it from dmesg. For the Intel just grep on INTEL

# dmesg | grep  INTEL
ad6: 38166MB <INTEL SSDSA2M040G2GC 2CV102HB> at ata3-master SATA150

So our new drive is ad6. Now setup to the drive If you choose the wrong device you might/WILL destroy all your data on that disk.

# dd if=/dev/zero of=/dev/ad6 bs=1k count=1
# fdisk -BI ad6
# disklabel64 -B -w -r ad6s1 auto
# disklabel64 -e ad6s1

Now you should be in your editor with the disklabel data. Arrow down to the bottom of the screen. You should see some sample labels

# EXAMPLE
#a:          4g          0    4.2BSD
#a:          *           *    4.2BSD

After the last line you will add your SSD setup, see the WARNINGS section of swapcache(8) about leaving room on the drive for proper wear leveling. For the 40GB drive 32GB should be the max size used for the cache.

Add this line.

b:  32g 0   swap

Now save the file.

Adding Disk to fstab

Edit /etc/fstab and comment out any existing swap partitions. Just add a # in front of the line.

#/dev/serno/JPC550HN25.s1b          none            swap    sw              0       0

Add your new device to fstab

/dev/ad6s1b          none            swap    sw              0       0

Setting swapcache to start on boot

To enable swapcache on boot edit /etc/sysctl.conf and add

vm.swapcache.read_enable=1
vm.swapcache.meta_enable=1

See swapcache(8) for other sysctl options like vm.swapcache.data_enable

Activating the swapcache

The easiest way at this point is to just reboot the machine.