Staggered spin up

[SNDS]

Hey folks,

 

So after much trepidation, I am going to swap out my Rocket 750 with 3 LSI 9207-16i cards. However, one of the things I liked about the Rocket was that it would do staggered drive spin up. I cannot find any information about whether the LSI 9207-16i cards support this. I'm using a single PSU (Seasonic Prime Titanium 1000) using Molex connectors and the case I have does not accommodate a second PSU. The problem I am concerned about is too much power draw upon boot (especially if a shutdown has to be affected for some reason (brown out with graceful shutdown with connected PSU). Does anyone know if these cards would support staggered spin up? If not, does anyone have an alternate card suggestion that has 4 8087 ports and supports staggered spin up?

Note: I have a storinator-like device and don't have nor will I have 45 drives in use for a long while, though that is the long term goal. Near term I am probably fine as I am only spinning up 10 drives, but long term I want to have a solution already implemented.

Edited October 4, 2019 by SNDS

[JonathanM]

Because of how unraid implements parity, staggered spinup is not able to be implemented without major design changes which are unlikely to be made.

 

When you first power up your system, the controller is in charge of spinup, and can manage it. However... after unraid is in charge, the drive controller no longer has any say in when drives are spun up or spun down. If you implement spin down for drives that have not been accessed, which is one of the major selling points of unraid, then when unraid gets a disk access request it will spin up the drive asap.

 

This is all fine and dandy when your power supply is properly sized for the number of drives that need to be spun up at once, which is ALL of them.

 

Picture this. Your array is idling, only one disk is spun up and reading, and a read error occurs. The first thing unraid does is recreate the data that should be in the spot that errored out from parity. That means ALL the parity array drives are immediately asked to spin up. If your power supply is not able to handle that, you will get multiple read errors, and possibly multiple disabled drives.

 

So.. here is the TLDR;

You either need to size your power supply to be able to spin up all your drives at once without any stress or issues, OR disable spindown so the only startup surge is on initial power up and can be managed by your controllers. Since most people that use unraid want to spin down unused drives, the normal advice given is size your power supply appropriately.

[SnickySnacks]

I was contemplating the same thing a while back.
A lot of it will depend on what kind of drives you are running

WD Red NAS drives pull less than 2A peak:

https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/western-digital/product/internal-drives/wd-red-hdd/data-sheet-western-digital-wd-red-hdd-2879-800002.pdf

While older WD Blue drives could use up to 3A, modern ones are also sub 2A:
https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/western-digital/product/internal-drives/wd-blue-hdd/data-sheet-wd-blue-pc-hard-drives-2879-771436.pdf

It would seem to me that even accounting for motherboard/cpu/etc you should easily be able to handle 30+ something drives before you need to think about expanding your PSU (Seasonic Titan Prime 1000 should have 83A on the 12V rail). If you're running 7200 RPM drives or something this may be closer to 20, but 10 drives should be no problem at all.

I am running 16 drives, I think, on a Seasonic 860 (71A) with no issues that I've seen. 

And, unless you are trying to absolutely max out your storage capacity, at some point you'll likely be replacing smaller drives with larger ones as you expand. Doesn't make as much sense to add four 3TB drives when two 6TB or one 12TB will do and likely be the same price or cheaper (parity, etc, I know....)

Edited October 4, 2019 by SnickySnacks