So, I have a NAS running TrueNAS Core with 16x HDD in RAID-2 (8 disks per VDEV) and i’m thinking to backup the pool and then create a new pool along with the metadata VDEV. But i’m not sure how many drives should i use for metadata VDEV. Will 2 drives in mirror work fine? Or do i need more?
Also, i wanted to mention that the data vdevs are 16x 16TB Seagate EXOS. Will these impact any performance or pool reliability as these are different as some are X16, X18 and X24. Secondly, with this many drives, would it really make sense to add a metadata vdev for faster traversing? I don’t think adding metadata vdev is going to increase the throughput but probably the responsiveness. Am i thinking correctly?
On a side note, i’m using Antec Signature 1300W to connect the drives using the original cables. Will be the drive safe? Any risk of catching fire or overload on the 5V rails?
Your PSU can provide 125W of 3.3v/5v (I guess combined). Your HDDs use at MAX 6.3w of 5v (this is the first time I’ve ever seen the manufacturer be kind enough to break down to wattage per voltage rail):
As for the sata power cables… uh thats what? 4.5amps per connector for 5v max (so thats 22.5w; but your drives will only ever use a bit more than 1amp per connector) - so with that in mind, lets round up to 1.5amps & assume you have 16awg wire for your sata power cables; you’d likely be good for around ~8 sata power plugs per wire (I’m certain your psu is even more conservative & has like… 5 plugs per wire). *Note that this is conservative math for likely very conservative specs
Anyway, all of that to say that you’re perfectly fine in terms of PSU & the original sata plugs/wires for what you’re doing currently doing - those max wattage draws are worst case brief scenario & your psu & wiring is likely also being conservative & could (likely) reliably pull more than they’re doing. Unless you’re doing something that is hitting the 3.3v line very hard (I doubt it).
…As far as special vdevs - I don’t mess with that because I don’t have any kind of SSDs with enough redundancy that I’d trust for that purpose. Lose your special vdev, lose the pool. I’d go triple mirror with enterprise grade sdds if I really had to.
Edit: do you really need a special vdev? Whats the use case? Is data backed-up anywhere else?
The redundancy should be equivalent for all vdevs. RaidZ2 (did you mean that with “RAID-2”?) = two drives may fail –> build a three way mirror for the Special Device.
Regarding the use case, it’s more of a archival but system remains operational on week or month basis. I’m not sure if it would benefit from adding special vdev but long time ago i tried on a test machine and the results were pretty good.
Maybe my math is off, but 150w/6.3 is around 23. That being said these are conservative values all around from the psu, awg, sata connectors, and hdds - likely you can pull more without issue.
Oh, wow. Makes sense. Didn’t know. Thanks for letting me know. So, would 3x mirrored drives for sVDEV would be fair enough? It’s a 16 bay disk (HDD) and i’m not sure if i would need sVDEV.
A Raid-Z2 pool would have a three way mirror sVDEV. You want the same redundancy for both sections. The Raid-Z2 could lose 2 drives and still function. You need that ability when you add the sVDEV so a three way Mirror can lose 2 drives and still function. 3 drives lost in either set and you lose the pool and all data.
