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Forum Discussion
Why UPS for Spin-Down?
Hi! Just a quick question I couldn't find the answer for. Why is it recommended to use an UPS, when you turn on HDD spin-down? How can data get lost? I'm doing an incremental backup once or twice a d...
We agree more than we disagree. One reason I recommend a UPS is that I lost a Duo v1 some years ago w/o one. Perhaps now I could have recovered it; one benefit of being active in the forum is that you learn stuff from other posters.
However, since I put the UPS in place I have always had controlled shutdowns (or recovered power before the battery discharged). I've had no issues with file loss with any of my ReadyNAS since then (now up to 4, though the duo v1 will be retired soon). Since a UPS costs about the same as a disk drive, it seems like good insurance to me.
On RAID, I guess I'd say it is more about maintaining availability than protection. If you can afford the drives, I think you get better protection with multiple copies on different jbod volumes. Certainly recovery is simpler (unless we are talking RAID-1).
On disks failing at the same time: there are studies suggesting that this is not just a lottery - that in fact disk failures are correlated in RAID arrays. Multiple failures happen much more often than the statistics predict. There are some reasons why this seems credible. People tend to purchase identical drives in batches - particularly the large data centers that were studied in this research. Even home NAS users also frequently buy new drives when setting up their NAS. The drives are likely to be in the same manufacturing lot, and shipped together. Also, drives in the same RAID chassis are under near-identical loads, experience near-identical temperature/vibration, are fed by the same power supply, etc. Identical drives, identical handling, identical environment -> failures happen close together.
EDIT- Just wanted to add that I have two friends who lost almost all their electronics due to a power surge (nearby lightening strikes in both cases). There was clear evidence that the surge went through their data cables as well as their power.
However, since I put the UPS in place I have always had controlled shutdowns (or recovered power before the battery discharged). I've had no issues with file loss with any of my ReadyNAS since then (now up to 4, though the duo v1 will be retired soon). Since a UPS costs about the same as a disk drive, it seems like good insurance to me.
On RAID, I guess I'd say it is more about maintaining availability than protection. If you can afford the drives, I think you get better protection with multiple copies on different jbod volumes. Certainly recovery is simpler (unless we are talking RAID-1).
On disks failing at the same time: there are studies suggesting that this is not just a lottery - that in fact disk failures are correlated in RAID arrays. Multiple failures happen much more often than the statistics predict. There are some reasons why this seems credible. People tend to purchase identical drives in batches - particularly the large data centers that were studied in this research. Even home NAS users also frequently buy new drives when setting up their NAS. The drives are likely to be in the same manufacturing lot, and shipped together. Also, drives in the same RAID chassis are under near-identical loads, experience near-identical temperature/vibration, are fed by the same power supply, etc. Identical drives, identical handling, identical environment -> failures happen close together.
EDIT- Just wanted to add that I have two friends who lost almost all their electronics due to a power surge (nearby lightening strikes in both cases). There was clear evidence that the surge went through their data cables as well as their power.
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