Step 2: Creating a ZFS storage pool

In this step we will take the virtual hard drives that we created in Step 1 and convert them into a ZFS Storage Pool.

Reconnect to the VM:
From terminal

BASH
```
./run xnat-21 ssh
```
Become root:
BASH
```
sudo -i
```

List disks:

BASH

root@xnat-21:~# fdisk -l
Disk /dev/sda: 68.7 GB, 68719476736 bytes
255 heads, 63 sectors/track, 8354 cylinders, total 134217728 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0004f458
   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048      499711      248832   83  Linux
/dev/sda2          501758   134215679    66856961    5  Extended
/dev/sda5          501760   134215679    66856960   8e  Linux LVM
Disk /dev/sdb: 25.8 GB, 25769803776 bytes
255 heads, 63 sectors/track, 3133 cylinders, total 50331648 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Disk /dev/sdb doesn't contain a valid partition table
Disk /dev/sdc: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 cylinders, total 16777216 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Disk /dev/sdc doesn't contain a valid partition table
Disk /dev/sdd: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 cylinders, total 16777216 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Disk /dev/sdd doesn't contain a valid partition table
Disk /dev/sde: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 cylinders, total 16777216 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Disk /dev/sde doesn't contain a valid partition table
Disk /dev/mapper/vagrant--vg-root: 67.9 GB, 67922558976 bytes
255 heads, 63 sectors/track, 8257 cylinders, total 132661248 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Disk /dev/mapper/vagrant--vg-root doesn't contain a valid partition table
Disk /dev/mapper/vagrant--vg-swap_1: 536 MB, 536870912 bytes
255 heads, 63 sectors/track, 65 cylinders, total 1048576 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Disk /dev/mapper/vagrant--vg-swap_1 doesn't contain a valid partition table

Our new disks are at /dev/sdb, /dev/sdc, /dev/sdd, and /dev/sde

/dev/sdb: 25.8 GB

Disk sdb is larger than the other 3. This is to accommodate non-SSD users. Explanation in the next step.

Create a ZFS pool:
SSD Users

BASH
```
zpool create -f tank raidz1 sdb sdc sdd sde
```
Spinning Disk Users

BASH
```
zpool create -f tank sdb
```
Spinning Disk Users

If your workstation/laptop does not have an SSD, do not use raidz1, this pool will become painfully slow. Your pool will be the same size as the raidz1 setup. In the raidz1 setup only 8GB of the first disk will be used by ZFS.
If you do not know the disk type of your workstation used the spinning disk command.
Confirm the pool is created:
BASH
```
root@xnat-21:~# zpool list
NAME   SIZE  ALLOC   FREE  EXPANDSZ   FRAG    CAP  DEDUP  HEALTH  ALTROOT
tank  31.8G   112K  31.7G         -     0%     0%  1.00x  ONLINE  -
```
The size of the pool may not be exactly the same.

ZFS Redundancy

We have created a virtual pool with raidz1 redundancy. However, this redundancy is virtual and still on a single disk. So why bother? We have actually protected our data from bit rot on a single disk. Should a sector become bad ZFS will detect it and repair it with the redundant virtual disks. Raidz1 is similar to RAID5, there is one parity sector for each stripe. However, raidz is not laid out like typical raid5, it does not always write to all the disks in a stripe. If there is only one sector it will write one data sector and one parity sector. A more detailed explanation is on Wikipedia: https://en.wikipedia.org/wiki/ZFS#RAID
Set some pool defaults:
BASH
```
zfs set compression=lz4 tank
zfs set sync=disabled tank                # Typically, we would not do this for a production pool.  It risks about 5 seconds of data loss.
zfs set primarycache=metadata tank        # This VM doesn't have much memory, let's cache what's most important.
```
ZFS Compression

We are using lz4 compression on all of our data. LZ4 is a light weight compression that is typically about 80-90% as effective at compressing data as gzip. However, it is very easy on the CPU and in almost all cases our pool will actually perform faster with LZ4 compression than no compression at all. XNAT data typically will get compressed about 20% with LZ4 compression.
Limit ZFS memory usage.
This is only necessary on a system with limited RAM such as our xnatdev VM. Typically ZFS will be run a dedicated server and be allowed to use all available RAM. In this case we are allocating 1/4 of our total RAM to ZFS. If you've given your VM more RAM adjust as you like.
Production ZFS servers typically start at 16gb RAM and in some cases over 1TB RAM. With only small fraction of that RAM, ZFS will not perform anywhere near its potential on this VM.
BASH
```
echo "options zfs zfs_arc_max=536870912" >> /etc/modprobe.d/zfs.conf
echo "536870912" > /sys/module/zfs/parameters/zfs_arc_max
```

Step 2 Complete

Continue to Step 3: Setting Up ZFS Folders