ZFS Correctly move /tmp from zpool to UFS on SSD

[korund]

Currently I have the following:

# mount

space/ROOT/default on / (zfs, local, noatime, nfsv4acls)
devfs on /dev (devfs, local, multilabel)
/dev/da0p1 on /ssd (ufs, local, noatime, noexec, soft-updates)
space on /space (zfs, local, noatime, nfsv4acls)
space/tmp on /tmp (zfs, local, noatime, nosuid, nfsv4acls)
space/usr/home on /usr/home (zfs, local, noatime, nfsv4acls)
space/usr/ports on /usr/ports (zfs, local, noatime, nosuid, nfsv4acls)
space/usr/src on /usr/src (zfs, local, noatime, nfsv4acls)
space/var/audit on /var/audit (zfs, local, noatime, noexec, nosuid, nfsv4acls)
space/var/crash on /var/crash (zfs, local, noatime, noexec, nosuid, nfsv4acls)
space/var/log on /var/log (zfs, local, noatime, noexec, nosuid, nfsv4acls)
space/var/mail on /var/mail (zfs, local, nfsv4acls)
space/var/tmp on /var/tmp (zfs, local, noatime, nosuid, nfsv4acls)

# cat /etc/fstab

# Device                Mountpoint      FStype  Options                         Dump    Pass#
/dev/da0p1              /ssd            ufs     rw,noexec,noatime               0       0
md99                    none            swap    sw,file=/ssd/swapfile,late      0       0

What would be the correct way to move /tmp from the pool? I guess just symlinking /tmp to /ssd won't work.

 

[obsigna]

How about creating another partition on the ssd (let's say /dev/da0p2) and mount that one onto the moint point /tmp instead of space/tmp?

 

[usdmatt]

If you have no free space on the SSD you could try a nullfs mount.

Create a /ssd/tmp directory and then:

/ssd/tmp      /tmp       nullfs     rw      0       0

You might need nullfs_load="YES" in /boot/loader.conf.

You could also do exactly the same as you're doing for swap - That seems to be using a memory disk, backed by the file /ssd/swapfile. Create a file of a reasonable size ( truncate -s 500M /ssd/tmpfile) then add to fstab, same as swap)

 

[SirDice]

I would suggest using tmpfs(5) for /tmp.

 

[korund]

How about creating another partition on the ssd (let's say /dev/da0p2) and mount that one onto the moint point /tmp instead of space/tmp?

Just add water record to /etc/fstab and it will move automatically after the reboot?

If you have no free space on the SSD you could try a nullfs mount.
...
You could also do exactly the same as you're doing for swap - That seems to be using a memory disk, backed by the file /ssd/swapfile. Create a file of a reasonable size ( truncate -s 500M /ssd/tmpfile) then add to fstab, same as swap)

I have plenty of space, just want to move /tmp out of HDD raidZ to the fast SSD.

 

[obsigna]

How about creating another partition on the ssd (let's say /dev/da0p2) and mount that one onto the moint point /tmp instead of space/tmp?

Just add water record to /etc/fstab and it will move automatically after the reboot?

Yes, like so:

# Device        Mountpoint      FStype  Options                 Dump    Pass#
/dev/da0p1      /ssd            ufs     rw,noexec,noatime       0       0
/dev/da0p2      /tmp            ufs     rw,noatime              0       1
...
...

 

[wblock@]

tmpfs(5) is faster than a UFS filesystem.

 

[obsigna]

tmpfs(5) is faster than a UFS filesystem.

May be. However, does this really count, given that read/writes are usually cached, and given that /tmp on a server usually holds only small amounts of data. How many nanoseconds can we expect to save per hour with tmpfs compared to ufs2?

 

[ANOKNUSA]

May be. However, does this really count, given that read/writes are usually cached, and given that /tmp on a server usually holds only small amounts of data. How many nanoseconds can we expect to save per hour with tmpfs compared to ufs2?

There isn't really a point in giving /tmp an entire disk. Just give it a gigabyte or two of RAM.

 

[wblock@]

For some applications, avoiding the round-trip overhead of a filesystem could be a real advantage. But it's nice to have an auto-clearing /tmp too.