[animeguru]

I didn't see it mentioned elsewhere on here, but I've done quite a bit of reading on the unRaid forums and a popular performance enhancing, risk mitigation strategy used is to have a cache drive that is the same size as your largest disk.

This leads significantly faster writes that can be scheduled for inclusion in the array during off hours with the added benefit of a ready 'hot spare' should a drive ever decide to die. You can then move the cache drive into the array and rebuild without having to wait to obtain a replacement drive.

Makes sense to me.

[edz2k9]

Hi there

I looked at caching, one thing I didn't fully understand from my reading is if the cache is used when writing to the server, e.g. is there a point at which it is not parity protected?

In my case the first solution to speed will be a motherboard update from ye olde spare box I have now which only has two onboard SATA ports and I'm adding some more via PCI. That will limit throughput and put my parity build on 3 2TB drives and a 2TB parity drive at ~ 24-36 hours I'm guessing in the first instance anyway?

[edz2k9]

For those who have unraid boxes a quick question. Has anyone cracked open an external USB drive (in this case a western digital 1TB elements drive like this one https://www.amazon.co.uk/Western-Digital...173&sr=8-1 and added it into an active array.

My initial server will be 3 2TB WD drives with a 2TB parity but once I've put all the media over from the USB NTFS WD element drives I'm thinking of then pulling them from the USB cases and adding them into the array giving me 2 more 1TB drives and keeping my other 2 1TB Seagate USB drives for onsite and offsite backup of important non-ripped material (photos etc).

Anyone tried this?

[vinistois]

I've ripped several drives out of several different usb cases. Shouldn't have any problems!

[edz2k9]

Thanks for that, vinistois, cool. That should give me a parity checked 8 TB array instead of the current 4 x 1TB USB drive / ubuntu JBOD thats presently in place. Plan is to split the current server back to being its original design goal of a mythtv server with squeezecenter running and have it and the rest of the system use the new file store for file access over NFS / SMB.

Ironically, the new server using spindown will probably use less power than the 4 wall-wart power supplies for the USB drives since they're just PSU units and dont reduce the power draw if the drives are idle (plus I've never been able to stop ubuntu spinning the drives up every 10-15 minutes no matter what I do)

[edz2k9]

Hi All

quick question on unraid / preclear / parity construction.

As I understand it preclearning the drive (A) finds any errors on the drive stopping them showing up in the live array and also stopping curruption of the parity and thus impacting the array and (B) speeds up the process of adding new drives to a running array.

Can someone who has been running an unraid box answer a couple of questions for me?

1. Can you preclear a drive from the server without taking the array down, e.g. add the drive then set it to preclear - not become part of the array - and thus let the server carry on without downtime?

2. When you add a precleared drive does the array then go completely offline until the parity is rebuilt? If so isnt this a little contra to the point of having a parity system to ensure continuity of service?


Any advice gratefully received.

[tabish121]

Hi All

quick question on unraid / preclear / parity construction.

As I understand it preclearning the drive (A) finds any errors on the drive stopping them showing up in the live array and also stopping curruption of the parity and thus impacting the array and (B) speeds up the process of adding new drives to a running array.

Can someone who has been running an unraid box answer a couple of questions for me?

1. Can you preclear a drive from the server without taking the array down, e.g. add the drive then set it to preclear - not become part of the array - and thus let the server carry on without downtime?

2. When you add a precleared drive does the array then go completely offline until the parity is rebuilt? If so isnt this a little contra to the point of having a parity system to ensure continuity of service?


Any advice gratefully received.

There are tools to preclear drives outside of the array and then once you add the precleared disk the array is immediately available again as the state of the drive is know and parity doesn't need to be rebuilt.

See the setup tutorial sections 6 and 7.
Configuration Tutorial

[smiffy1989]

The array can be online while parity is built.

[edz2k9]

Cool stuff. I will take a close look at that, thanks.

BTW
Anyone who needs to mount a USB stick inside their case be aware that maplin has usb header to 2 usb female sockets for internal use for £4.99 http://www.maplin.co.uk/internal-usb-pla...ins-346517

Probably cheaper online somewhere but I picked one up along with 12cm ultraquiet fan for £9

[edz2k9]

Right you lot have done it now, placed the order for my pro license with limetech.

Cant carry on now until the drives, psu and 4 in 3 unit turn up.

[edz2k9]

After much reading and re-reading I've entered the "in for a penny" mindset, dropped my plan to use my old motherboard with 2 sata 1 ports and ordered a new motherboard bundle with 4 high speed sata connections a 16x pcie slot, 2 pcie x1 speed slots and a legacy pci slot.

My initial build will use the motherboard sata ports and I'll stick the pci cards on ebay before buying a pcie sata card.

Still brings the build in under £500 including drives (4 x 2TB WD) and the pro unraid license not bad for a parity protected 6TB array!

[edz2k9]

Hmmm this is turning into a blog

New board turned up from Novatech and the machine's now running away preclearing drives (unmenu and other scripts installed)

the only issue is I'm still not convinced that this motherboard wont have to go back. Although its not on the HPA problem list it is a Gigabyte board GA-M68MT-S2 (something that wasnt shown in the novatech details which listed it as an nvidia chipset board - which it is) and I'm still awaiting confirmation that it wont start splurging bios backup data all over one of the array drives. If so its distance selling regs return time on the mobo unfortunately

[bnevets27]

You can turn off HPA. There may or may not be an option in the bios. I forget what it is called in bios but it is alone the lines of what you said, "backup bios data to hard drive"

If the option is not in bios, look for a bios update. Later versions of gigabyte bios added the option to turn it off HPA.

I've been using a gigabyte board for about 2yrs now without any problems. As long as you know you have to turn off HPA and have it turned off, you should be fine.

[edz2k9]

You can turn off HPA. There may or may not be an option in the bios. I forget what it is called in bios but it is alone the lines of what you said, "backup bios data to hard drive"

If the option is not in bios, look for a bios update. Later versions of gigabyte bios added the option to turn it off HPA.

I've been using a gigabyte board for about 2yrs now without any problems. As long as you know you have to turn off HPA and have it turned off, you should be fine.

Thanks for that, I did check through the advanced options, ctrl-f1 (extra) advanced options and the bios settings and theres no option for HDD on this board. This is also the only bios version available for this (newish?) board. I posted over at the gigabyte forum and got this response from one very helpful member:

Hi there,

no need to worry, the BIOS image won't automatically be written to the HDD. You would manually have to enable this option if it is available in the BIOS. If it is present, it is normally disabled by default.

Just take care if you decide to use Windows 7 as an OS as this automatically creates an HPA when installing.

I've also contacted Novatech to see what they say but for now the drives are pre-clearing on the console 1-4 screens (phase 2 about 50% in) once thats done I'll reboot then check syslog for HPA entries if there are none I'll push on with getting the array (apart from parity) up and running, get files over then enable parity.

Speaking of parity, the current thinking seems to be (as above) to assign it after data has copied over but how does formatting the parity drive come into this or is it not a format as such since its holding the parity bits from the other drives?

Thanks all

Ed

[edz2k9]

Preclear completed in 28hrs on all four drives.

Next I'll set up the drives and assign them, get some files over and reboot to check for HPA issues.

If none surface it will be time to copy the collection over before getting the parity online.