I don't know the technical hurdles, but the majority of NAS products out there support hot swapping of all the drives in the array.  Currently I can only find indications about possible hot swapping of the cache drive.  In production environments, shutting down a file server to replace a failed drive is very difficult, and often unacceptable unless done after hours.  So, I would like to suggest adding hot swap support for all drives to the Roadmap.

I don't know the technical hurdles, but the majority of NAS products out there support hot swapping of all the drives in the array.  Currently I can only find indications about possible hot swapping of the cache drive.  In production environments, shutting down a file server to replace a failed drive is very difficult, and often unacceptable unless done after hours.  So, I would like to suggest adding hot swap support for all drives to the Roadmap.

 

Here's the main problem with hot swap: it is not "universal", that is, you can put together a set of components for a particular server, and get hot swap to work with those components (or substitute some components until you get it to work).  Then you can call that your "product" and now you support hot swap.  However, trying to get hot swap to work with all combinations that home server-builders come up with would be verrrry fustrating.....

I'd say it would be even more frustrating than trying to get S3 sleep to work.

I'd say it would be even more frustrating than trying to get S3 sleep to work.

 

Very similar.

So maybe not a true "hot swap", but some kind of more live way of detecting and mounting a drive without having to reboot?  Is it that much more complex than mounting an external drive via USB?  Or would it be possible to come up with a subset of hardware that unRAID would support for hot swap.  Don't support all permutations of available hardware, but maybe just a handful of the more common setups a lot of people are using?  Am I showing my ignorance?  

So maybe not a true "hot swap", but some kind of more live way of detecting and mounting a drive without having to reboot?  Is it that much more complex than mounting an external drive via USB?  Or would it be possible to come up with a subset of hardware that unRAID would support for hot swap.  Don't support all permutations of available hardware, but maybe just a handful of the more common setups a lot of people are using?  Am I showing my ignorance?  

That is almost exactly the same capability available now with the SNAP user-add-on.

 

It will auto-mount the drives.

 

Joe L.

So maybe not a true "hot swap", but some kind of more live way of detecting and mounting a drive without having to reboot?  Is it that much more complex than mounting an external drive via USB?

 

If you have AHCI, Linux already does that.

 

And if you don't, you can use the scsiadd package.

A big issue is that unRAID was written with the intent of matching the drive serial numbers to the logical array disk slots for the array assignment. Then, the array is started with the disks assigned. So, this part would likely have to be completely changed to also allow a drive to rebuild if it was suddenly changed.

 

Peter

 

 

A big issue is that unRAID was written with the intent of matching the drive serial numbers to the logical array disk slots for the array assignment. Then, the array is started with the disks assigned. So, this part would likely have to be completely changed to also allow a drive to rebuild if it was suddenly changed.

 

Depends of what kind of hot swap you are talking about.

 

Do you want the ability to remove a dead drive, add a replacement, run some commands, and stop/restart the array (not the entire server) fairly quickly.... if so, that can be done now.  The point is to not have to reboot the server.

 

If you want to take a running drive, and just pop it out and pop a new one back in and have it all magically start working w/o some user intervention, then no, that ain't gonna happen.

The OP message indicated he's interested in no down-time disk swaps.

 

Peter

The OP message indicated he's interested in no down-time disk swaps.

 

Yes, that was my preference.  To me that's what hot swapping within a protected array is all about. 

 

If you want to take a running drive, and just pop it out and pop a new one back in and have it all magically start working w/o some user intervention, then no, that ain't gonna happen.

 

Without the sarcasm, that is the general idea.  I'm not asking for something that doesn't exist in the NAS industry already.  There's nothing magical about a drive being detected by the OS and the array performing a scripted operation to institute the replacement under protection.  The difference, as Tom illustrated in the beginning, is that other vendors have 100% control over the hardware they support, and unRAID does not.  So relegating this to the "Never" shelf with Printer Support and Multiple Arrays is fine if it's unfeasible.  What would be at least useful would be a user script or protocol that automated much of the replacement procedure to help eliminate as many manual operations as possible.  The less technically complicated these tasks are, the more comfortable people will be with unRAID, and its perceived user friendliness will improve.

 

Some people are able to get S3 and WOL to work with their particular hardware.  Why isn't Hot Swap the same way?  Even if unRAID doesn't support it outright, couldn't it be configurable?

I think what I'd like to be able to do is hot plug a new drive, preclear it and then be able to add it to the array without having to reboot.  I don't care about hot-unplugging from the array, just hot-plugging a new drive.

 

I know that to hot plug requires the mobo or sata adapter ports have to support it and I have that equipment - that part is cheap and easy to get. 

I think what I'd like to be able to do is hot plug a new drive, preclear it and then be able to add it to the array without having to reboot.  I don't care about hot-unplugging from the array, just hot-plugging a new drive.

 

I know that to hot plug requires the mobo or sata adapter ports have to support it and I have that equipment - that part is cheap and easy to get. 

You can do that now.  There is nothing that will prevent it that I am aware of.

I think what I'd like to be able to do is hot plug a new drive, preclear it and then be able to add it to the array without having to reboot.  I don't care about hot-unplugging from the array, just hot-plugging a new drive.

 

I know that to hot plug requires the mobo or sata adapter ports have to support it and I have that equipment - that part is cheap and easy to get. 

You can do that now.  There is nothing that will prevent it that I am aware of.

 

If you pull a hot drive out of unRAID won't it be detected as failed? Then if you hot plug in a new drive what happens?

I think what I'd like to be able to do is hot plug a new drive, preclear it and then be able to add it to the array without having to reboot.  I don't care about hot-unplugging from the array, just hot-plugging a new drive.

 

I know that to hot plug requires the mobo or sata adapter ports have to support it and I have that equipment - that part is cheap and easy to get. 

You can do that now.  There is nothing that will prevent it that I am aware of.

 

If you pull a hot drive out of unRAID won't it be detected as failed? Then if you hot plug in a new drive what happens?

 

emhttp does nto auto refresh and I am not sure if or how often it might check the system for changes.  If a drive is pulled from the array it would be detected as failed, just like a drive going offline.  Replacing that drive would probably require a stop of the array, adding the drive, refreshing emhttp, then adding the drive to the array in place of the one that failed.

 

NOTE: I have not tried ANY of the ABOVE and DO NOT suggest anyone try it unless they feel like possibly screwing something up!!!

I think what I'd like to be able to do is hot plug a new drive, preclear it and then be able to add it to the array without having to reboot.  I don't care about hot-unplugging from the array, just hot-plugging a new drive.

 

I know that to hot plug requires the mobo or sata adapter ports have to support it and I have that equipment - that part is cheap and easy to get. 

You can do that now.  There is nothing that will prevent it that I am aware of.

 

I think you are right that with the right hardware you can hot plug a drive, manually determine its device ID, then Preclear it, but I don't think that unRAID knows about drives that are not in its original Drive Inventory, determined at boot.  Probably easy enough to test:  with an appropriate machine, boot and start the array, then hot plug a drive, then stop the array, go to the Devices page, and see if the new drive appears in a drive dropdown list.  If it is not there, then a reboot is required.  (for the test, it may or may not be needed to start and stop the array.)

What's the syntax to manually determine a drive ID?  I would be happy to test this theory one one of my many test servers.

I think what I'd like to be able to do is hot plug a new drive, preclear it and then be able to add it to the array without having to reboot.  I don't care about hot-unplugging from the array, just hot-plugging a new drive.

 

I know that to hot plug requires the mobo or sata adapter ports have to support it and I have that equipment - that part is cheap and easy to get. 

You can do that now.  There is nothing that will prevent it that I am aware of.

 

If you pull a hot drive out of unRAID won't it be detected as failed? Then if you hot plug in a new drive what happens?

I DID NOT say you could do it with a drive assigned to the array.

unRAID cannot deal with a hot-plug on  drive assigned to the array.

 

The previous post asked about a drive NOT in the array.  I'm pretty sure it will be detected when it is plugged in, and it could be cleared, and the array could then be stopped, the disk assigned, and the array re-started without rebooting the entire server.

 

Joe L.

What's the syntax to manually determine a drive ID?  I would be happy to test this theory one one of my many test servers.

 

ls -l /dev/disk/by-id

 

that should get you all the disks that are installed in the system

I think you are right that with the right hardware you can hot plug a drive, manually determine its device ID, then Preclear it, but I don't think that unRAID knows about drives that are not in its original Drive Inventory, determined at boot.  Probably easy enough to test:  with an appropriate machine, boot and start the array, then hot plug a drive, then stop the array, go to the Devices page, and see if the new drive appears in a drive dropdown list.  If it is not there, then a reboot is required.  (for the test, it may or may not be needed to start and stop the array.)

Ok, you might need to restart emhttp

 

killall emhttp

nohup emhttp &

 

and then assign the drive to the array.  No need to reboot just to re-start emhttp.

So, with v5b5 being release with the following feature:

- webGui: support hot plug of hard drives when array is Stopped (limited h/w testing).

 

... this addresses my issue of having to do a full server shutdown to add / replace a drive in the array.  Hopefully this feature won't prove to be problematic.  One step closer to live swaps, which I know is on the "Never" shelf right now.  Thanks Tom!