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X-RAID Volume Calculator - Site Edition - v2.11
By: infotinks, Updated: 2022-03-19

* NOTE: RN is for ReadyNAS, RD is for ReadyDATA
* NOTE: Here is a btrfs calculator by carfax that has similar mechanics to xraid. It helps visualize how the different sized drives get split into regions (partitions on the NAS) and how btrfs can intellegintly raid it. The ReadyNAS does this as well using XRAID RAID5 and XRAID RAID6 technology, which is accomplished thru a combo or partitions + mdadm + ext4 or btrfs. ext on ReadyNAS 4.x and 5.x and btrfs on ReadyNAS 6.x. This online tool helps visualize these regions and partitions as they are seperated by different colors. It gives you the raw size in GB or TB. However my calculator converts to GiB and TiB and also takes into account filesystem and other overhead, so it comes out closer to the expected value (with respect to ReadyNAS).

     ReadyNAS: Intel, X86 (RN Firmware 4.2.x / RAIDiator 4, and OS 6)
     ReadyNAS: ARM (ReadyNAS RAIDiator 5.x, and OS 6)
     ReadyNAS: SPARC (ReadyNAS Firmware 4.1.x)
     ReadyDATA (RD Firmware 1.x.x)

    For ReadyNAS 6.x use Intel or ARM depending on unit.

    For ReadyNAS OS 6 & ReadyDATA use 0 GB snapshot (So just skip this step for ReadyNAS OS 6 and ReadyDATA). This is meant for units which you have to initialize the snapshot size when you setup the unit at Factory default (so the 4.1.x, 4.2.x, and 5.x - the units which use EXT and LVM). We use 0 for the ReadyDATA and ReadyNAS 6.x, because those units use ZFS and BTRFS, respectively. ZFS or BTRFS are used for volume management and as filesystem together ZFS and BTRFS do not require pre-allocating space for snapshots during initialization of the device (during Factory default).


Please fill out this field Accordingly


    - If you dont know what this does just leave this as 1 (the default value). Also this number should always be an INTEGER and not have a DECIMAL (although the calculation will still work if its a decimal number is given).
    - This is a multiplier field. It will just multiply all of the answers by this number. This is useful if you have multiple vdevs. For ReadyNAS 4.1.x & 4.2.x & 5.x use 1 (1 is the default). For ReadyNAS 6.x use 1 (unless you have done vdev horizontal expansions). For ReadyDATA this is the number of vdevs you have. Running "zpool status" from SSH (SSH is not supported under warranty) can show you the number of vdevs in your volumes, and the number of drives in each vdev.
    - NOTE: If you have multiple VDEVs & thus a multiplier bigger than 1, please make sure each vdev is the same size (same number of storage drives - performance enhancing drives such as ZIL or ARC do not count), also when you do the calculation make sure you fill out STEP 3, the drives, as you have a single vdev (not the whole unit).
    - EXAMPLE: if you have a 24 drive array (each drive 4 TB) that is made of 3 vdevs. Then fill out STEP 3 with 8 drives (24 divided 3) of size 4000 each (4 TB), and here put 3 for the multiplier.
    - KEY EXAMPLE: When you expand a ReadyDATA volume from a volume that is 5 drives in a RAID 5, you have 1 VDEV/RAID group, then you add 5 more drives to your ReadyDATA, and you expand the initial volume, creating a 2nd VDEV. So now you have 10 drives of 2 VDEVS each housing 5 drives - we call this RAID 50x2. Now take another 5 drives and expand that same initial volume, now you have RAID 50x3, which has 15 drives (3 vdevs, each with 5 drives). Each of those vdevs gives you 1 drive for parity, and 4 drives for storage capacity. So in total after the 2 expansions, aka RAID 50x3, you have 4*3=12 storage drives, and 1*4 parity drives. You can lose up to 4 drives, considering they only fail in different vdevs. A better way to see it, is you can only lose up 1 drive in each of the 3 VDEVS and still have your volume running. As soon as you lose 2 drives in any VDEV that will go up to. Of course in RAID 60x3 you can lose up to 2 drives and no more per VDEV, for a total of 2*3=6 parity drives that you can lose. (dont think that any individual drive holds the parity, each drive holds parity, the parity stripes with ZFS are dynamic and variable and spread across each drive, this variability fixes alot of issues of traditional RAID 5.). If you lose more than 1 drive in a vdev in RAID 5, or 2 drives in a vdev in RAID 6, your volume goes offline and you can use data recovery services to see if Netgear can recover your data.

NETGEAR KB - Chirpas Article

Why Your Hard Drive Shows Less Space Than Advertised