Optane and IMDT

The different operating modes of Intel's Optane drives, as high-performance block devices and as lower-cost memory

Intel's newer Optane drives are available today in block device format. When a server with Optane drives boots normally, for example into Ubuntu or CentOS, they appear as block devices. For example, looking at one of our Accelerate With Optane servers:

# lsblk 
NAME       MAJ:MIN    RM    SIZE    RO    TYPE    MOUNTPOINT 
sda              8:0  0   223.6G    0     disk   
├─sda1           8:1  0     512M    0     part    /boot/efi 
├─sda2           8:2  0     1.9G    0     part    [SWAP] 
└─sda3           8:3  0   221.2G    0     part    /
 nvme0n1       259:0  0   698.7G    0     disk 
└─nvme0n1p1    259:1  0   209.6G    0     part 
nvme3n1        259:2  0   698.7G    0     disk 
nvme2n1        259:3  0   698.7G    0     disk 
nvme1n1        259:4  0     3.7T    0     disk 
└─nvme1n1p1    259:5  0    186.3G   0     part 
# free -g              
              total        used        free      shared  buff/cache   available 
Mem:            187           0         185           0           1         185 
Swap:             1           0           1


In the above, you can see that there are 5 drives:

  • sda , the 240GB SAS boot drive
  • nvme0n1 , the 4TB NAND NVMe drive
  • nvme1-3 , the three 750GB Optane drives


The Optanes appear as 3 block devices, on which you can make filesystems and mount them.

In addition, there is 192GB of memory.

In IMDT mode, on the other hand, you will not see block devices. Instead, 1, 2 or even all 3 of the Optanes will look like regular memory. The advantage to doing so is that they function like memory, but can be as low as 1/4 of the cost.


Here is the same output from a server running 2 of the Optanes as IMDT:

# lsblk 
NAME    MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT nvme1n1 259:0    0 698.7G  0 disk /rabbitmq 
sda       8:0    0 223.6G  0 disk 
├─sda2    8:2    0   1.9G  0 part [SWAP] 
├─sda3    8:3    0 221.2G  0 part / 
└─sda1    8:1    0   512M  0 part /boot/efi 
nvme0n1 259:1    0   3.7T  0 disk
 
# free -g
              total        used        free      shared  buff/cache   available 
Mem:           1370           0        1369           0           0        1366 
Swap:             1           0           1


The output has only 1 Optane at nvme1n1 , but has 1.5TB of memory.