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Forum Discussion
XRAID-2 Hot Spare or Expansion with FlexRaid
I've seen a few messages a year old regarding hot spare support on X-RAID. I would really like to see hot spare support on the ReadyNAS pro with XRAID2. I know there is auto expansion to consider but perhaps you could leave the drive out during setup and designate a bay as the hot spare bay, which then wouldn't be autoexpanded.
I realize that FlexRaid has hot spare capability, but FlexRaid (at least to my knowledge) requires deleting the volume and recreating it if you want to perform an expansion.
Either allowing drive additions in FlexRaid without volume recreation or allow hot spare designation in XRAID-2 would be helpful.
I realize that FlexRaid has hot spare capability, but FlexRaid (at least to my knowledge) requires deleting the volume and recreating it if you want to perform an expansion.
Either allowing drive additions in FlexRaid without volume recreation or allow hot spare designation in XRAID-2 would be helpful.
15 Replies
- You can use the dual redundancy feature with X-RAID2 to protect against dual-drive failures. This would be more redundant than having a hot spare as standby as you're leaving a window for an additional failure during the rebuild onto the spare.
- Thanks yoh-dah...
I realize that I could use the dual redudancy feature but I don't like the storage overhead cost. What I'd like to do is put 5 drives in it with raid 5 (which also doesn't have the write overhead) and then have the sixth standing by for the failure. I realize this leaves my vulnerable during the failure but I think its a good compromise at least until a 10 bay readynas appears in that case I'd probably go with the dual redundancy... - Umm, raid 5 with a hot spare would provide the same storage capacity and using the same amount of drives as a dual redundant raid 6 volume.
Plus, while the hot spare was resyncing, a 2nd failure would kill the volume. This wouldn't happen with raid 6 or an otherwise dual redundant volume.
Same overhead, same capacity, raid 5 with a hot spare is riskier. - Also keep in mind that even with write penalty for RAID 6, performance is still above what a normal PC can push -- see http://www.readynas.com/?page_id=450#Performance .
- What is the dual redundancy feature with xraid 2 and how do I enable it?
yoh-dah wrote: You can use the dual redundancy feature with X-RAID2 to protect against dual-drive failures. This would be more redundant than having a hot spare as standby as you're leaving a window for an additional failure during the rebuild onto the spare. chirpa wrote: Enhanced X-RAID2 to support dual-redundancy, allowing for protection from 2 disk failure while maintaining the flexibility of X-RAID2 auto-expansion. To use X-RAID2 in dual-redundancy mode, you will need to backup your data and restore after performing a factory default to set the ReadyNAS in dual-redundancy mode. When you request a factory default and reboot, there’s a 10-minute window where RAIDar will allow you to select the RAID mode. At this time, select X-RAID2 with dual-redundancy option, and you’re good to go. You will need a minimum of 4 disks to see this option, and you will need the RAIDar 4.1.5 release supporting this. - It would be nice to be able to switch to dual redundancy without setting to factory defaults. I can see a lot of people who start off with 3 drives and move to 4 and 5 drives that would want to switch from single to dual redundancy.
- Another data point on the RAID5+spare vs RAID6. With a hot spare, there is generally no regular I/O happening to this drive, even though it is spun up -- I don't believe RAIDiator supports regular background scrubbing. That means that the spare has the possibility of gathering faults just by being present over time, and a rebuild at a crucial moment could render your volume unprotected. With the double parity, you do have some degree of overhead from an extra write, sure, but if you're already going to render that drive as unused space, I suspect the benefit of having it as part of an actively used parity stripe is of more value than just letting it randomly spin and /maybe/ be useful as a spare someday.
- I just build a new Pro Biz with 5 2TB Hitchachi drives. I wouldn't have picked it, but was NEVER given a choice to use dual redundancy. I was only given the choice to X-RAID2 or Flex-RAID with auto, 1, or 2.
I was told I might not have been given the dual redundancy option due to the version of RAIDar? I would think whatever came on the disk that came with the pro should have had the right versions of things (even if not latest) to perform dual redundancy, but I wasn't given that choice.
I don't know that I would have chosen dual redundancy for the reasons given above.
I have supported hundreds of servers over many years and never saw a two drive failure.
Lew - Coming to ReadyNAS with a 3200 replacing a Netapp S550, so I was hoping to configure with dual parity *and* a hot spare. Would really like to see this option made available, seems a shame to lose the expandability.
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