Multiple General Questions about Unraid

[plantsandbinary]

Hi, I would appreciate it if anyone could answer even some of these questions. I've scoured the wiki but it's quite dated and these are the questions I still have left.

 

Mover related stuff:

 

• Why can the 'Mover' not be stopped once it is started?
• Why is it not possible to see how long the 'Mover' takes to move files, but there is a time estimate for read check and parity check etc?
• Why is it possible to Spin Down the disks when the 'Mover' is running? Surely this would interfere with the mover?
• When I run the 'Mover' if at 100% cache usage, why does it stop running by itself at 75% usage? I want it to completely free up the cache by writing to the storage drive.
• I have 1x 4TB WD Red for Parity and 1x 4TB WD Red for storage, my average write speed from the 'Mover' is only about 40MB/s (to both parity and storage) which seems really slow. My drive write speed is rated at 160MB/s (but I realise that is max sequential write speed). Still, is 40MB/s normal?
• If I attempt a graceful shutdown of the server via the Unraid panel (Shut Down) and the 'Mover' is running, what is the process Unraid will make? Does it finish the parity and storage write that it is on?
• At times it seems the 'Mover' is not doing anything, but it still says that it is running and this prevents me from being able to shut my machine down. Is there some way to guarantee that the 'Mover' is actually working, that isn't just looking at read/write IOs on the Main page?

 

Cache:

 

• My server is constantly complaining that some Appdata files are stored outside of the cache, even though the setting is 'Cache Only'. I've invoked the 'Mover' multiple times with Docker disabled and set 'Appdata' as 'Cache Only', but I ultimately still get this error. What's causing this?
• Is it at all possible to protect only a single SSD cache drive as part of the parity? If it's possible, is this even worth doing?

 

Parity:

 

• Is dual parity any way faster than single parity for parity checking and writing, or is it literally the same as single parity, but just more secure?
• Will setting a SSD as the parity drive make a parity rebuild faster? Will it make literally anything regarding parity read/write/creation faster?

 

Unraid OS & USB:

 

• I'm using a Sandisk Extreme 64GB USB 3.0 drive for my Unraid OS, yet Unraid seems to use barely 1GB of storage on the drive, leaving the rest entirely untouched. Am I ever going to need that other 63GB for anything in the future? I realise I could store OS .iso files on it for VMs but I don't need to do that.
• Can Unraid run well (stable/normally) from a fast SD or MicroSD card?
• Is Unraid open source, or are some parts of it open source? I looked but I couldn't find any real information on this, but searches seemed to suggest it isn't.
• The Wiki says that SSD usage in the array is experimental, is this still the case or is it considered stable now to run an array entirely from SSD drives?

 

Windows based question:

 

• If I connect to a different network on my laptop e.g. at school. Then return home and connect to my home network. I cannot see my SAMBA Unraid share. I need to actually restart my laptop before the network appears. Does anyone know why this happens?

 

Big thanks to literally anyone who bothers to answer even a single question!

[Taddeusz]

I can't speak to most of this but as far as when shares are set to "Cached Only" the mover will NOT attempt to move those files to the cache even if there are files on the array. The mover completely ignores shares that are set to "Only". You must set the cache setting to "Prefer" for the mover to be able to move those files from the array to the cache.

[Taddeusz]

Conversely, if you set a share's cache mode to "No" the mover will also ignore those shares and NOT move files from the cache to the array.

[JorgeB]

2 hours ago, plantsandbinary said:

Why can the 'Mover' not be stopped once it is started?

It can be done on the console by typing:

mover stop

 

[Squid]

2 hours ago, plantsandbinary said:

Why is it possible to Spin Down the disks when the 'Mover' is running? Surely this would interfere with the mover?

The disk(s) it needs to write to will simply spin back up again.

[primeval_god]

Let me take a crack a a few of these, I welcome anyone more knowledgeable to correct me or flesh out my answers if I necessary. I continue to learn new things about unRAID all the time.

On 10/29/2018 at 4:43 PM, plantsandbinary said:

Parity:

• Is dual parity any way faster than single parity for parity checking and writing, or is it literally the same as single parity, but just more secure?

Dual parity is not faster, in fact because of the overhead of seeking to parity block on a second disk the extra calculations it is in most cases slower. Its benefit is the ability to recover from dual simultaneous drive failures.

On 10/29/2018 at 4:43 PM, plantsandbinary said:

• Will setting a SSD as the parity drive make a parity rebuild faster? Will it make literally anything regarding parity read/write/creation faster?

I dont believe that it would gain you any additional speed since parity operations depend on not just the parity drive but all disks in the array (assuming uniformly sized drives) and in the case of writes both the parity drive and at least one of the disk drives. I think this would also affect the lifespan of the SSD since the parity drive gets many more writes than other drives in the array. Not to mention the difficulty of finding an SSD as big or bigger than the largest disk in your array. That said i believe that a very few have tried or are using all ssd arrays for some special purpose.

On 10/29/2018 at 4:43 PM, plantsandbinary said:

Unraid OS & USB:

• I'm using a Sandisk Extreme 64GB USB 3.0 drive for my Unraid OS, yet Unraid seems to use barely 1GB of storage on the drive, leaving the rest entirely untouched. Am I ever going to need that other 63GB for anything in the future? I realise I could store OS .iso files on it for VMs but I don't need to do that.

No. Unraid does not need near that much space on the flash drive nor is the USB 3.0 really required. I dont remember the actual requirements but a 4-8G is plenty. The unRAID OS is kept intentionally small to allow it to run entirely from RAM. When unRAID boots the OS is loaded into RAM and then the USB drive is only used minimally for persisting configuration files.

On 10/29/2018 at 4:43 PM, plantsandbinary said:

Can Unraid run well (stable/normally) from a fast SD or MicroSD card?

This one is a little more complex. A few people do use flash cards as a boot drive for unRAID. The speed is not really an issue since, as mentioned above, the drive is primarily used during boot. The issue is finding a card reader that will work for unRAID. unRAID's licencing system is based on the GUID of the USB flash drives. Most reputable brands of USB drives have a unique GUIDs for each individual USB drive. Some lesser brands do not and these drive cant be used as a boot drive for unraid. For USB card readers it is far less common for them to have unique identifiers, making many (or maybe most) of them unsuitable for use with unRAID. 

On 10/29/2018 at 4:43 PM, plantsandbinary said:

Is Unraid open source, or are some parts of it open source? I looked but I couldn't find any real information on this, but searches seemed to suggest it isn't.

 Not entirely, but i believe that some parts are. I think a good portion, maybe all, of the Web GUI is still open source. The secret sauce of unRAID that is the array driver is not.