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Readynas Duo V2 - Raid1 and xRaid2

talkingduck
Aspirant

Readynas Duo V2 - Raid1 and xRaid2

I've been reading through a few posts here and the documentation(RAIDiator 5.3 SW Manual_3Jul12.pdf) and have a few questions about how to setup my RAID.

I have a Duo V2 which means I have a maximum of two bays. I will insert two 2TB drives in each bay which means I will have a maximum capacity of 2TBs if I used RAID1 or xRAID2.

Data protection is very important to me so I would like to make sure that my configuration gives me the best protection if I have a disk failure/unit failure.

Please correct me if I am wrong:

RAID1 will mean DISK1 and DISK2 will be exact clones of each other.

    Which in theory means I should be able to unplug the unit and switch the disks around in the bay and everything will still be the same.
    I can insert either DISK1 or DISK2 into a Desktop PC and read all the data.


xRAID2 will mean DISK1 and DISK2 are not exact clones but DISK2 can be used to recreate DISK1

    I cannot swap the disks in the bays around and expect everything to work
    I can not insert either DISK1 or DISK2 into a Desktop PC and read the data because it's a proprietary format


Same question for both RAID1 and xRAID2

If a drive were to fail I switch off the unit and then replace it with a drive of equal size. On start up the working drive will be copied to the replacement drive. How would the unit know which drive is primary, if DISK1 failed would I have to move DISK2 into bay1 first?

For me RAID1 sounds like the better option if my assumptions are all correct, the key point for me is that I could if I wanted to pull out either drive and insert into a Desktop PC.

If this is the case I can then have a 3rd drive DISK3 which I can interchange with DISK2 and use it to have a backup stored elsewhere.

Thank you for reading, sorry for the long winded question I just want to make sure I setup everything correctly.
Message 1 of 9
mdgm-ntgr
NETGEAR Employee Retired

Re: Readynas Duo V2 - Raid1 and xRaid2

talkingduck wrote:

RAID1 will mean DISK1 and DISK2 will be exact clones of each other.

    Which in theory means I should be able to unplug the unit and switch the disks around in the bay and everything will still be the same.
    I can insert either DISK1 or DISK2 into a Desktop PC and read all the data.


Correct. Though I don't recommend switching around the disk order. Also to read the data in a PC you'd need to use 3rd party software or use Linux, start the RAID, scan for the volume, mount it etc.
talkingduck wrote:

xRAID2 will mean DISK1 and DISK2 are not exact clones but DISK2 can be used to recreate DISK1

    I cannot swap the disks in the bays around and expect everything to work
    I can not insert either DISK1 or DISK2 into a Desktop PC and read the data because it's a proprietary format


Incorrect on all counts:
It is X-RAID (used by v1 units) that uses a parity disk. Disk 1 and Disk 2 both have the partition table on them just like RAID-1 (in fact X-RAID2 with two disks uses RAID-1).
You could power down and then rearrange the order of the disks, but it isn't recommended.
Neither X-RAID (used by v1 units) nor X-RAID2 (used by v2 units) uses a proprietary RAID format. No ReadyNAS has ever used a proprietary RAID format. The X-RAID expansion scripts are the things that are proprietary. The process for mounting disks from a X-RAID2 array in Linux is a bit simpler than that for X-RAID disks.
talkingduck wrote:

If a drive were to fail I switch off the unit and then replace it with a drive of equal size. On start up the working drive will be copied to the replacement drive. How would the unit know which drive is primary, if DISK1 failed would I have to move DISK2 into bay1 first?

You can use hotswap (replace failed disk while NAS is on). The NAS should remember which disk was already in the NAS even if you do a cold swap. However just to be safe if doing a cold swap you should insert a blank unformatted disk.
talkingduck wrote:

For me RAID1 sounds like the better option if my assumptions are all correct, the key point for me is that I could if I wanted to pull out either drive and insert into a Desktop PC.

Your assumptions about X-RAID2 are wrong. I'd go with X-RAID2 as it's not any worse than RAID-1 in this regard.
talkingduck wrote:

If this is the case I can then have a 3rd drive DISK3 which I can interchange with DISK2 and use it to have a backup stored elsewhere.

No, this kind of so-called "backup" strategy inevitably leads to data loss. Please read Preventing Catastrophic Data Loss. There's a reason why NetGear puts so much time and effort into backup options like ReadyNAS Replicate (makes backing up to another ReadyNAS over the internet securely easy) and Dashboard backup, and one of the reasons USB ports are included is for backups.
Message 2 of 9
StephenB
Guru

Re: Readynas Duo V2 - Raid1 and xRaid2

mdgm wrote:
...I'd go with X-RAID2 as it's not any worse than RAID-1 in this regard.
I would too. Another benefit of X-RAID2 is that the array can be expanded in the future by upgrading to larger drives.
Message 3 of 9
talkingduck
Aspirant

Re: Readynas Duo V2 - Raid1 and xRaid2

Thank you for the replies, the biggest worry for me is if the unit fails and I can't find a replacement system for xRaid2 drives.

Since the Duo V2 does not support xRaid1, I assume those people with xRaid1 formatted drives are stuck (well if you couldn't buy the old Duo V1 second hand). If the Duo V3 comes out and doesn't support xRaid2 I will have to use a Linux system to copy my data to the new system. If I was using Raid1 presumably I could just plug these drives into any supporting Raid1 unit and carry on?

Is the only real advantage of xRaid2 over Raid1 the ability to swap 1 of the drives for a larger size? For example if I wanted to upgrade my data on to larger disks I would replace DISK1 with a large drive wait for the unit to resync the data and the replace DISK2 with an equally large drive and wait for the sync?
Message 4 of 9
mdgm-ntgr
NETGEAR Employee Retired

Re: Readynas Duo V2 - Raid1 and xRaid2

X-RAID2 with two disks is RAID-1. It's no less likely to be migrateable to a new ReadyNAS system than a RAID-1 volume
Message 5 of 9
talkingduck
Aspirant

Re: Readynas Duo V2 - Raid1 and xRaid2

Ok thanks for all your help, I think I will go with the xRaid2 then 🙂
Message 6 of 9
CJM1
Aspirant

Re: Readynas Duo V2 - Raid1 and xRaid2

Hi all.

Sorry to re-open this post, but I have the same question as talkingduck started out with reg. RAID1 vs. X-RAID2, and I am confused by the "RAIDiator 5.3 SW Manual_5Sep12.pdf"-manual. On page 20, last paragraph in said manual, it is disclosed that

"X-RAID2 uses the first disk to store data, and the second disk to store parity information that allows it to re-create data if a disk fails in this two-disk system, the usable storage space is one disk. In a three-disk system, the usable storage space is two disks, and in a four-disk volume, the usable storage space is three disks."

Therefore, to a non-skilled person as myself, RAID1 seems to give better protection than X-RAID2 in case of a failing disk because as described by talkingduck, using RAID1 I would have two identical disks. In X-RAID2 I would have a data disk and a parity disk; and if the data disk fails I only have the parity disk?!?

Thus, could someone please explain whether X-RAID2 with two disks provides RAID1 protection or not? And please elaborate:-) Because said paragraph, in my view, indicates X-RAID2 provides a lower level of protection than RAID1.

Best regards
CJ
Message 7 of 9
mdgm-ntgr
NETGEAR Employee Retired

Re: Readynas Duo V2 - Raid1 and xRaid2

I don't think that manual is written well. Only X-RAID on the Sparc units (run RAIDiator 4.1.x or earlier) uses a dedicated parity disk. If either disk failed you could replace it and the array would rebuild.

X-RAID2 distributes the parity amongst the disks. It does not have a dedicated parity disk. X-RAID2 with two disks is making use of RAID-1.
Message 8 of 9
CJM1
Aspirant

Re: Readynas Duo V2 - Raid1 and xRaid2

Thanks for clearing that out.
BR
CJ
Message 9 of 9
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