Physically rearranging drives cables, swapping position on mobo/pci card

I currently have 8 SATA II drives, 4 connected directly to the motherboard and 4 connected to a Promise PCI (not PCI-e) card.  My system is maxed out in terms of available SATA slots.  I have noticed the PCI bottleneck when performing several IO operations at once.  Therefore, I would like rearrange my cabling a bit so that my largest and most used drives (parity + 3 data drives) are connected directly to the motherboard, and my smallest and least used drives (4 data) are connected to the PCI card.  I believe the process is as simple as:

 

1) Stop and array and power down.

2) Rearrange the cables to my heart's content.

3) Power up and start the array.  unRAID will recognize the drives' new positions and everything will be normal.

 

However, I wanted to double check here before I actually did anything.  Am I good to go, or is it more complicated than this?

 

I have also read in other threads suggestions about shuffling your data around so that the most often accessed data is confined to a few drives, thereby minimizing unnecessary drive spin up.  Sounds like a good idea to me, but how would I go about doing it?  I use User Shares, not Disk Shares, so I don't really know where any particular file is physically located.

I currently have 8 SATA II drives, 4 connected directly to the motherboard and 4 connected to a Promise PCI (not PCI-e) card.  My system is maxed out in terms of available SATA slots.  I have noticed the PCI bottleneck when performing several IO operations at once.  Therefore, I would like rearrange my cabling a bit so that my largest and most used drives (parity + 3 data drives) are connected directly to the motherboard, and my smallest and least used drives (4 data) are connected to the PCI card.  I believe the process is as simple as:

 

1) Stop and array and power down.

2) Rearrange the cables to my heart's content.

3) Power up and start the array.  unRAID will recognize the drives' new positions and everything will be normal.

 

However, I wanted to double check here before I actually did anything.  Am I good to go, or is it more complicated than this?

 

I have also read in other threads suggestions about shuffling your data around so that the most often accessed data is confined to a few drives, thereby minimizing unnecessary drive spin up.  Sounds like a good idea to me, but how would I go about doing it?  I use User Shares, not Disk Shares, so I don't really know where any particular file is physically located.

Just in case....

Before you re-arrange the cabling, go to the "devices" page of the management interface and do a screen-print.  That way, you can re-assign the drives to their respective slots if the software does not "figure it out" on its own when you move the cabling.  Odds are it will do it on its own, but if you by chance use a controller connector that was previously vacant, it might think it lost a drive. (when it is actually just waiting to be re-assigned on the devices page to the correct slot in the array)

 

Joe L.

Good call, thank you for the tip.

I'm very glad I did that, because now I don't know what to do.  Here's the screencap of the devices page that I took of the working server before I messed with anything (I only took a screencap of the devices page, not the main page):

Before:

 

After physically rearranging the cables and disks into what I hope is an optimal layout (I have pictures to post later, too), I booted the server back up and now I see:

After:

I took a screencap of the main page too, if that helps:

After:

(notice the error: Disk in Parity Slot is not the Biggest)

 

My gut tells me to use the drop down menus on the devices page to make it look like it used to, before I rearranged everything.  So unassign all the drives, then assign each drive to the slot it used to occupy, then start the array.  But of course, I want to make sure that is the right thing to do before I do anything, the risk of losing data is just too great.

 

Note: I noticed this forums ability to attach documents after I already hosted the pics on imageshack.  I attempted to attach the pics to this post, but it told me the files were too big.  I hope the imageshack pics are acceptable.

I'm very glad I did that, because now I don't know what to do.  Here's the screencap of the devices page that I took of the working server before I messed with anything (I only took a screencap of the devices page, not the main page):

Before:

 

After physically rearranging the cables and disks into what I hope is an optimal layout (I have pictures to post later, too), I booted the server back up and now I see:

After:

I took a screencap of the main page too, if that helps:

After:

(notice the error: Disk in Parity Slot is not the Biggest)

 

My gut tells me to use the drop down menus on the devices page to make it look like it used to, before I rearranged everything.  So unassign all the drives, then assign each drive to the slot it used to occupy, then start the array.  But of course, I want to make sure that is the right thing to do before I do anything, the risk of losing data is just too great.

 

Note: I noticed this forums ability to attach documents after I already hosted the pics on imageshack.  I attempted to attach the pics to this post, but it told me the files were too big.  I hope the imageshack pics are acceptable.

Your gut instinct is correct.  Use the drop-down boxes to assign the drives to their original slots in the array.

Just be certain that the parity drive is assigned to the parity slot in the array.

 

You should be able to just use the "Start" button once you get the drives assigned back where they were.

 

Do not use the "Restore" button, and do not use the "Format" button (if it appears) and you should not have any chance of losing data.

 

Joe L.

Yet again your words warrant a huge sigh of relief, thank you very much.  I've tested various files, and everything is hunky-dory.

As long as you have a screen capture of original device assignment. in the situation like this you can do as following, that is also what i had done last time when i re-arrange cables.

 

(a) make sure unRaid is stopped, most likely it would since there are "so many" missing disks from unraid perspective.

(b) go to Device page, un-assigned all disks, even those unraid had figured out but they might be at "wrong" slot.

© Now start from parity disk, re-assign each one of them base on your original device assignment. Each disk has its own unique ID, for example your original parity disk

    is "WCAU45951367".

(d) Once you finish this manual re-assignment, go back to Main and start unRaid. at this time unraid should be able to recognize those disks and report back a healthy

    system status.

 

Keep in mind, whenever you make change in your unRaid device arrangement, take a screen capture or print out Device page from Unraid's web page for your own record.

 

That's exactly what I did, and it worked perfectly.  Good walkthrough. (maybe wiki-worthy?)

Yes, it should be in the wiki, but where?  That is a question I often have trouble with, and this is a good example.  I'd be glad to hear opinions on it, and better yet, see someone add it.

 

I'm sure some of the wiki placement and wording decisions I have made could be greatly improved, often just too arbitrary and subjective.  I just added a wiki link to some good advice about installing cables to the Hardware Compatibility page, where it did not belong, but I couldn't think of a better place for it.  Not every thing fits well into the FAQ, because a FAQ is for questions of more general interest, not TOO specific or not very closely related to the subject of the FAQ.

 

The walk through is good, but I'm not sure about step (b), about the necessity of unassigning ALL disks.  Perhaps someone can explain why they think that is necessary.  Until now, I had not felt that unassigning any but the disks that are wrong was necessary.

The walk through is good, but I'm not sure about step (b), about the necessity of unassigning ALL disks.  Perhaps someone can explain why they think that is necessary.  Until now, I had not felt that unassigning any but the disks that are wrong was necessary.

I do not think it is necessary to unassign all the drives.  However, it might make the task of assigning them easier, since you cannot assign a drive assigned elsewhere.

 

Joe L.

 

The walk through is good, but I'm not sure about step (b), about the necessity of unassigning ALL disks.  Perhaps someone can explain why they think that is necessary.  Until now, I had not felt that unassigning any but the disks that are wrong was necessary.

 

 

Well, There are two reasons unassigned ALL drives first is better

 

(a) In some situations, even those not-missing disks that unRaid had figured out actually had been assigned by unRaid to WRONG slot. For example in my case, a previous data disk after cable re-arrangement was assigned as parity disk by unRAID. eventually I have to unassign those disks at wrong slots first by comparing them with my previous configuration one at a time which is very troublesome.

 

(b) Had un-assigned all disks actually would give user all disk to choose from in drop-down menu when re-assign. As long as user has a copy of previous configuration, s/he can just need to re-assign them from drop down menu one by one. A very straightforward process.

 

 

So if I understood, you changed the cabling but didn't renumber the drives. Is there a way to renumber drives as well as change the cabling without losing data?

 

I want to switch out four 750 GB drives and replace them with 1 TB and 1.5 TB drives. I thought I'd do this by moving the 750 GB drives (disks 1-4) to my eSATA breakout box, and putting in the bigger drives in their place. I want to then call the 750 GB drives, disks 13-16. Instead of replacing the drives one by one and go through the data rebuliding etc. I simply want to copy the data from disks 13-16 to disks 1-4 using Midnight Commander... and then delete the data on disks 13-16. Is this feasible?

 

Thanks for any help in advance.

So if I understood, you changed the cabling but didn't renumber the drives. Is there a way to renumber drives as well as change the cabling without losing data?

 

I want to switch out four 750 GB drives and replace them with 1 TB and 1.5 TB drives. I thought I'd do this by moving the 750 GB drives (disks 1-4) to my eSATA breakout box, and putting in the bigger drives in their place. I want to then call the 750 GB drives, disks 13-16. Instead of replacing the drives one by one and go through the data rebuliding etc. I simply want to copy the data from disks 13-16 to disks 1-4 using Midnight Commander... and then delete the data on disks 13-16. Is this feasible?

 

Should be possible, by using the Trust My Array procedure.  Unassign them and reassign them as 13-16, then do the procedure, and abort the ensuing parity check, if you have very recently run it.  Then you can begin adding and formatting the new drives, then moving data.  I would be careful to do everything just one step at a time, and verify it worked correctly.  Don't try to move drives and assignments and connections at the same time.

If you are eventually going to install a new drive and let unRAID preclear it and add it then you might as well just replace the old one and rebuild onto the new one. Both procedures will take about the same amount of time. I'm pretty sure the drive rebuild will allow you to access the array. It will be busy and slow but you can access data. On the other hand, the array stays offline while adding a new drive until the drive is cleared and added so you will have a period of array downtime.

 

If you plan on using Joe's pre-clear script to prepare the new drive then moving the existing ones might be a good idea.

 

I would let a parity check finish before doing any of this major work though.

 

Peter

 

 

The walk through is good, but I'm not sure about step (b), about the necessity of unassigning ALL disks.  Perhaps someone can explain why they think that is necessary.  Until now, I had not felt that unassigning any but the disks that are wrong was necessary.

 

 

Well, There are two reasons unassigned ALL drives first is better

 

(a) In some situations, even those not-missing disks that unRaid had figured out actually had been assigned by unRaid to WRONG slot. For example in my case, a previous data disk after cable re-arrangement was assigned as parity disk by unRAID. eventually I have to unassign those disks at wrong slots first by comparing them with my previous configuration one at a time which is very troublesome.

 

(b) Had un-assigned all disks actually would give user all disk to choose from in drop-down menu when re-assign. As long as user has a copy of previous configuration, s/he can just need to re-assign them from drop down menu one by one. A very straightforward process.

 

 

 

I agree.  While the 'unassign all' step isn't strictly necessary, it makes the process easier and a bit more foolproof.  We could make a note that this step is optional, if you all prefer.

 

Edit: I have added this to the wiki, please review it here:

http://lime-technology.com/wiki/index.php/Improving_unRAID_Performance#Hardware_Tips

 

It is pretty ugly, it would be nicer if it could be itemized into a bulleted or numbered list.  Its a bit verbose as well, I somehow managed to stretch this procedure into 12 steps, but it is very thorough.

Edit: I have added this to the wiki, please review it here:

http://lime-technology.com/wiki/index.php/Improving_unRAID_Performance#Hardware_Tips

 

Very nice!  I was really hoping someone would find a way to add it, and then I got an impulse this afternoon myself (jumped the gun), entered a FAQ entry for it, and when I saved it, discovered you had just created the Move Largest and Fastest Data Drives Off PCI Bus section with it.  So I edited the new FAQ entry to include a link to your work.  The FAQ entry is here:  "What is the safe way to rearrange disk numbers, assignments, slots, etc?"  I think there are comments and tips in each that complement the other.

 

would be nicer if it could be itemized into a bulleted or numbered list.  Its a bit verbose as well, I somehow managed to stretch this procedure into 12 steps, but it is very thorough.

 

I find they often 'stretch', as you generalize it for the widest number of situations, and add more helpful tips.  Nice bullets are made with leading asterisks, numbered lists are made with the pound symbol.  Just replace the '(1)' with '#', and let each one start the line.  There is very good MediaWiki help readily available, with a link on the left of every wiki page.

Thanks everyone for your answers.

 

If you are eventually going to install a new drive and let unRAID preclear it and add it then you might as well just replace the old one and rebuild onto the new one. Both procedures will take about the same amount of time. I'm pretty sure the drive rebuild will allow you to access the array. It will be busy and slow but you can access data. On the other hand, the array stays offline while adding a new drive until the drive is cleared and added so you will have a period of array downtime.

 

If you plan on using Joe's pre-clear script to prepare the new drive then moving the existing ones might be a good idea.

 

I would let a parity check finish before doing any of this major work though.

 

Peter

 

 

I thought of that, but the problem with replacing the drives one at a time is that the drive cages I'm using are a real pain to frequently open up and futz around with. I'm not using a hot-swap system and each replacement essentially requires that I take much of the system apart. My next build will be with a Norco case.

 

Edit: I have added this to the wiki, please review it here:

http://lime-technology.com/wiki/index.php/Improving_unRAID_Performance#Hardware_Tips

 

It is pretty ugly, it would be nicer if it could be itemized into a bulleted or numbered list.  Its a bit verbose as well, I somehow managed to stretch this procedure into 12 steps, but it is very thorough.

 

if you want to keep "What you type is what you see" then the most easy way is to quote your paragraph with markup tag <pre></pre>. I had modified it for you.

Thanks for the help RobJ and GK20.  I'm new to editing wiki's.

 

I made it look like I originally wanted: Wiki

It does look much better!  One point though, step 10 about un-assigning the drives is not optional.  The part that is optional is un-assigning drives that happen to be already correct.  I thought you might prefer to reword that.

Ah yes, good point.  I removed the bit about it being optional, and changed the wording a bit.