Scratch Disk

Scratch Disks are helpful for keeping temporary or persistant data outside of the FMADIO host capture system. Many times the OS disks is unable to be used due to capacity or location.

Scratch Disks can be run as a RAID0 or RAIDx group of drives, allow you the system flexible allocation of the total storage capacity of the system between Capture vs Analytics.

ScratchDisk Configuration

Step 1) Assign physical disks

Start by editing the disk configuration file

/opt/fmadio/etc/disk.lua

Then moving serial numbers from the CacheDisk section to the ScratchDisk section.

For example moving a single disk (serial number "22443E9DC54E") from ssd8 -> scr0

Before:

  CacheDisk =
    {
        ["22443E9D204F"]        = "ssd0",
        ["22223AD5BFC3"]        = "ssd1",
        ["22443E9D3AFF"]        = "ssd2",
        ["22443E9DC543"]        = "ssd3",
        ["22443E9D2076"]        = "ssd4",
        ["22443E9D3B41"]        = "ssd5",
        ["22443E9D3B65"]        = "ssd6",
        ["22443E9D20A4"]        = "ssd7",
        ["22443E9DC54E"]        = "ssd8",
    }
    ,
    ParDisk =
    {
        ["22443E9D2087"]        = "par0",
    }
    ,
    RaidDisk =
    {
    }
    ,
    ScratchDisk =
    {
    }
    ,
    OSDisk =
    {
    ["50026B7685513F33"] = "os0",
    }
    ,

renameing ssd8 to scr0

After:

    CacheDisk =
    {
        ["22443E9D204F"]        = "ssd0",
        ["22223AD5BFC3"]        = "ssd1",
        ["22443E9D3AFF"]        = "ssd2",
        ["22443E9DC543"]        = "ssd3",
        ["22443E9D2076"]        = "ssd4",
        ["22443E9D3B41"]        = "ssd5",
        ["22443E9D3B65"]        = "ssd6",
        ["22443E9D20A4"]        = "ssd7",
    }
    ,
    ParDisk =
    {
        ["22443E9D2087"]        = "par0",
    }
    ,
    RaidDisk =
    {
    }
    ,
    ScratchDisk =
    {
        ["22443E9DC54E"]        = "scr0",
    }
    ,
    OSDisk =
    {
    ["50026B7685513F33"] = "os0",
    }

Save the file.

This can be repeated for as many disks as you require, please keep the numbering sequential e.g. scr0, scr1, scr2, scr3 etc so the system can map it correctly.

Step 2) Reboot the system

Rebooting is required as the system needs to rename the mount points in /opt/fmadio/disk

Step 3) Create RAID partition

Create the RAID0 partition using mdmadm as follows. Change the appropriate fields to create a RAID0 2 disk partition or more.

sudo mdadm --create /dev/md1 --force --verbose --level=raid0 --raid-devices=1 /opt/fmadio/disk/scr0

Or for a 2 disk Scratch Partition

sudo mdadm --create /dev/md1 --force --verbose --level=raid0 --raid-devices=2 /opt/fmadio/disk/scr0  /opt/fmadio/disk/scr1

The output will look something like below

Step 3) Create Filesystem

The partition now exists on /dev/md1 we need to create a filesystem next so it can be used in a general purpose way. Run the following command to create an EXT4 based Scratch Disk partition

sudo mkfs.ext4 /dev/md1

Example output looks like below

Step 4) Confirm the filesystem mounts correct

Next confirm th file system mounts correctly, by creating a test file on the partition

sudo mount /dev/md1 /mnt/store1

Then creating a file and confirming, such as below

Step 5) Confirm automatic mounting

Reboot the system and confirm the ScratchDisk gets mounted automatically on boot to

/mnt/store1

The test file created above should exit, example below

Capture Metadata on ScratchDisk

In some cases its best to locate the Capture Filesystems Metadata onto the scratch disk. A few extra steps in addition to the above steps are required.

Step 1) Create stream directory

Create a stream directory on the ScratchDisk such as below

sudo mkdir stream

Example output looks like the following

fmadio@fmadio100p3-539:/mnt/store1$ sudo mkdir stream
fmadio@fmadio100p3-539:/mnt/store1$ ls -al stream
total 8
drwxr-xr-x    2 root     root          4096 Sep  7 20:26 ./
drwxr-xr-x    4 root     root          4096 Sep  7 20:26 ../
fmadio@fmadio100p3-539:/mnt/store1$