Clearing Confusion on AF Drives


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Don't add the jumper, that won't help at all.

 

You have two options.  If you are the patient type, then let the drive run through a full preclear (at that speed it will take days, even a week maybe).  You can still use the rest of the drives in the server while the preclear is running.  Once it completes, check the final output report for errors.  If there are any errors, RMA the drive.  If there are none, then run it through another pass of preclear.  If it runs at full speed, great.  If it runs slow again, then cancel the preclear and RMA the drive.

 

If you are impatient, or just don't want to bother with the above, then just RMA the drive immediately.  Claim that it failed your diagnostic tests (which is true), and the vendor or manufacturer should replace it free of charge.

 

I only recommend the first option because I once saw a drive (also a WD EARS) that ran at about half speed during the first cycle of preclear, then full speed for every subsequent one.  By being patient with the drive and testing it twice I ended up with a perfectly good drive sooner and will less hassle than if I had just immediately RMA'd it.  Still, your drive is running so slow that I'm not confident that it will end up being OK.

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  • 6 months later...

Okay, now I have a question.  According to Hitachi, the 3TB drives they manufacture are not 4K aligned drives, and in fact use 512 byte sectors.  Preclearing using the non-AF switch did indeed start them at sector 63.  However, when formatting them with GPT via unRAID they were forced to start on sector 1.  I thought unRAID would respect the precleared sector alignment and maintain it, but in fact it did not.  Isn't that a bad situation if the drive isn't aligned the way it was manufactured to be?  Does GPT require AF alignment, or was this just an assumption?  Is there a way to realign the drives to sector 63 AFTER they have been partitioned, and without data loss?  

 

This is with v5b11.

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Okay, now I have a question.  According to Hitachi, the 3TB drives they manufacture are not 4K aligned drives, and in fact use 512 byte sectors.  Preclearing using the non-AF switch did indeed start them at sector 63.  However, when formatting them with GPT via unRAID they were forced to start on sector 1.  I thought unRAID would respect the precleared sector alignment and maintain it, but in fact it did not.  Isn't that a bad situation if the drive isn't aligned the way it was manufactured to be?  Does GPT require AF alignment, or was this just an assumption?  Is there a way to realign the drives to sector 63 AFTER they have been partitioned, and without data loss?  

 

This is with v5b11.

drives over 2.2TB use GPT partitions.  in Linux, when a GPT partition is defined, there is a "protective" MBR put into place to make older legacy utilities think the entire disk is in use.  That is why it looks like it starts on sector 1.

 

Instead, the actual GPT partition starts much further into the sectors, and is in fact aligned to a 4k boundary.

 

No, you cannot change the "protective" MBR, nor would the GPT partition work if you tried.  Basically, leave it alone.  It knows what it is doing....

 

Joe L.

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  • 2 months later...

Hi Folks,

 

At the real risk of opening up this can of worms again, I am finding a lot of material that seems to have conflicting advice regarding Advanced Format drives.

 

I have a brand new installation of unRAID 4.7 and 7 brand new Western Digital Caviar Green WD20EARX (being the replacement to the EARS previously). They are all empty and I only just started the pre-clear process yesterday on the first drive.

 

It appears that I don't need to worry about putting the jumper onto the new Western Digital drives and to simply pre-clear each drive, and then assign them within the unRAID interface.

 

Is that the case? There appears to be a lot of contradictory information out there which was correct prior to the 4.7 release of unRAID.

 

Some information regarding the latest WD drive, and latest unRAID release would be appreciated.

 

Thanks folks,

Mike.

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Thanks for your post BRiT.

 

I am using unRAID 4.7 - no problem there, haven't installed any jumpers - that much became clearer after some more reading, so good to have that confirmed.

 

The 4K alignment format is the bit that has me a tad confused though - the guides seem to indicate to invoke the following command line to pre-clear:

 

./preclear_disk.sh -A /dev/sda

 

If I understand this correctly, -A (capital) means MBR Aligned, -a (small 'a') means unaligned.

 

I have only done one of my WD20EARX drives - and it successfully completed last night after 23 hours with no errors according to the log. I'll invoke the command for the other six once I'm comfortable I'm taking the right path.

 

It appears that I'm using the correct command line - can you confirm?

Thanks for your help.

Mike.

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  • 3 weeks later...

If I understand this correctly, -A (capital) means MBR Aligned, -a (small 'a') means unaligned.

Wrong.

 

-A indicates the partition will start on sector 64

-a indicates the partition will start on sector 63.

 

All sectors are 512 bytes.

Sector 63 will therefore align on a 512 byte boundary.

Sector 64 will therefore align on a 4096 byte boundary AND on a 512 byte boundary.  (4K Aligned)

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  • 2 months later...

Folks, I've hunted but cannot seem to find this answer, so apologies if it's a silly question. :P

 

I'm running 4.7 with MBR: 4k aligned.  All drives are AF.

 

I found an old, non-AF drive that I want to add to the array.

 

Can I add it, or is that a bad idea?  Also, I intend to run the pre-clear script as per normal.

 

thanks!

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  • 2 weeks later...

I have been experiencing freezing when streaming blu-rays from my unraid server.  I have seen this behavior for quite a while.  I am wondering if I did something wrong when formatting my drives.  So I am wanting to remove 1 drive at a time and run pre-clear on the drives then readd it to the array.  I am running unraid V4.7.  Right now I see in the unraid consoles under disk settings it states "Default Partition Format=MBR:Unaligned.  My drives are WD20EARS.  From extensive reading I think I need to do the following:

 

Change the setting to MBR 4k aligned

 

remove the jumpers to my hard drives

 

I have 1 parity and 5 disks.

 

My array contains a lot of data (primarily dvd's and blu-rays.)

 

So I am wondering the procedure I should follow to accomplish my goal.  Like when should I change the unraid console to MBR 4k aligned etc.

 

What commands should I use to properly format my drives? example preclear_disk.sh -A dev/sdX (would this be correct?)

 

Should I do the following to accomplish this:

Stop the array

Remove the disk from the array

Start the array

Preclear the disk

stop the array

readd the disk

start the array

start a parity check

 

Once the parity check is complete, repeat the above procedure.

 

Thanks for any help you can provide.

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I have been experiencing freezing when streaming blu-rays from my unraid server.  I have seen this behavior for quite a while.  I am wondering if I did something wrong when formatting my drives.  So I am wanting to remove 1 drive at a time and run pre-clear on the drives then readd it to the array.  I am running unraid V4.7.  Right now I see in the unraid consoles under disk settings it states "Default Partition Format=MBR:Unaligned.  My drives are WD20EARS.  From extensive reading I think I need to do the following:

 

Change the setting to MBR 4k aligned

 

remove the jumpers to my hard drives

 

I have 1 parity and 5 disks.

 

My array contains a lot of data (primarily dvd's and blu-rays.)

 

So I am wondering the procedure I should follow to accomplish my goal.  Like when should I change the unraid console to MBR 4k aligned etc.

 

What commands should I use to properly format my drives? example preclear_disk.sh -A dev/sdX (would this be correct?)

 

Should I do the following to accomplish this:

Stop the array

Remove the disk from the array

Start the array

Preclear the disk

stop the array

readd the disk

start the array

start a parity check

 

Once the parity check is complete, repeat the above procedure.

 

Thanks for any help you can provide.

Correct procedure.  However if you added the "jumper" to those EARS drives already, then you ARE already partitioned correctly.  The jumper electrically adds one to the sector being requested, so the MBR:unaligned is transformed electrically to one that is aligned.   

The only way performance would be improved is if you had installed the jumper on the wrong pins.

If, as you say you have jumpers installed on the correct pins, you ALREADY have the most optimal settings for your disks.    The procedure you are thinking of will ONLY put your data at risk.    (In other words, others have lost data when something goes wrong, or they do something wrong)  In some cases, the disk had to be RMA'd.  Some have reported they do not like having the jumper settings reverted.

 

The symptoms you describe probably have nothing to do with how the disk is configured, but far more with the networking.

 

Joe L.

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If this is a networking issue, I am not sure how.  I am running a gigabit switch (HP Procurve 1400-8g).  My Mobo is an approved server quality Mobo (SUPERMICRO MBD-X8SIL-F-O) with gigabit nics.  Cat5e cabling.  I am streaming the blu-ray's with both Sagetv HD300 and HD200.  I have posted before on the board about this issue but I did not seem to get much help resolving this issue.  I realize it is something about my setup because there are a lot of people with unraid and streaming movies and they do not have any issues.  I am to the point of desperation hoping to find the issue, otherwise I might have to figure out a different way for storage and steaming.

 

My sage tv server records HD tv and the extenders stream the HD video without a hiccup.  I can even stream blu-ray's from my WHS without a hiccup.  I am really stumped as to what could causing the freezing.

 

I wanted to update people on this issue in case someone is having a similar problem.  My problem was sagetv related.  Some plugin (I have not had time to figure which one) was causing the freezing.  I uninstalled all plugins and my streaming stopped freezing.

Thanks for taking the time to help.

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  • 3 weeks later...

I've searched a fair bit but I'm not getting anywhere!  Maybe it's just me worrying, but I want to get it right first time!

 

I'm currently running unraid 4.7 on a HP N40L.  I've currently got 1xSamung HD103UJ as my parity drive and data drives are 1xSamsung HD103UI & the 250Gb Seagate drive that came with the N40L.  I precleared all of them WITHOUT the -A and they are currently set as MBR-unaligned in settings.

 

So, my issue is that I need more space.  This set up was originally a test rig to see how unraid would go, and I liked it! :) and it's now running just the way I like it with all the extra bits I wanted running smoothly.  I just purchased a Seagate ST2000DM001 http://www.seagate.com/internal-hard-drives/desktop-hard-drives/barracuda/?sku=ST2000DM001 because it seemed better than the WD Greens, and only $120AU.  I hoped to preclear this drive, then use it as a new parity drive, and use the 1Tb parity drive as a data drive but I checked on the forums & wiki first and now I'm more confused than ever!  I'll be adding more 2Tb drives as I need the space so I want to get it right now and not have to fix up a mistake later.  I've also got a 120Gb WD drive as a apps drive mounted with SNAP (not sure if you need that info)

 

So, do I preclear this new AF drive with a -A or without?  I'm confused, and if I change MBR to 4K Aligned undersettings with my current drives install will it all go BOOM.  My data is all backed up on my PC, and an external drive, so if I have to start with a clean slate, I suppose I will have to.  I do hope to upgrade to 5.0 when it goes final.

 

Thanks in advance for your help.  ;D

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I've searched a fair bit but I'm not getting anywhere!  Maybe it's just me worrying, but I want to get it right first time!

 

I'm currently running unraid 4.7 on a HP N40L.  I've currently got 1xSamung HD103UJ as my parity drive and data drives are 1xSamsung HD103UI & the 250Gb Seagate drive that came with the N40L.  I precleared all of them WITHOUT the -A and they are currently set as MBR-unaligned in settings.

 

So, my issue is that I need more space.  This set up was originally a test rig to see how unraid would go, and I liked it! :) and it's now running just the way I like it with all the extra bits I wanted running smoothly.  I just purchased a Seagate ST2000DM001 http://www.seagate.com/internal-hard-drives/desktop-hard-drives/barracuda/?sku=ST2000DM001 because it seemed better than the WD Greens, and only $120AU.  I hoped to preclear this drive, then use it as a new parity drive, and use the 1Tb parity drive as a data drive but I checked on the forums & wiki first and now I'm more confused than ever!  I'll be adding more 2Tb drives as I need the space so I want to get it right now and not have to fix up a mistake later.  I've also got a 120Gb WD drive as a apps drive mounted with SNAP (not sure if you need that info)

 

So, do I preclear this new AF drive with a -A or without?  I'm confused, and if I change MBR to 4K Aligned undersettings with my current drives install will it all go BOOM.  My data is all backed up on my PC, and an external drive, so if I have to start with a clean slate, I suppose I will have to.  I do hope to upgrade to 5.0 when it goes final.

 

Thanks in advance for your help.  ;D

You will be using your new disk as the parity disk.  Since 4k-allignment is compatible with ALL drives, use it.  Odds are your new drive does not  care.  The ONLY drive affected by alignment was one model of a seagate drive.  All others wok fine regardless of where the partition starts.  (Some unRAID users are anal about having everything configured identically... in this case, it does not matter, the array will not blow up, or lose data if you have a mix of drive partition alignment.)

 

So.... preclear... (only to exercise the drive and ensure it does not die an early death) then replace the parity disk with it and let parity get re-constructed onto it. 

 

Once you know it is working fine (give it a week or two) you can re-use the old 1TB disk as a data drive.

 

Joe L.

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  • 4 months later...
All others wok fine regardless of where the partition starts.  (Some unRAID users are anal about having everything configured identically... in this case, it does not matter, the array will not blow up, or lose data if you have a mix of drive partition alignment.)

 

Running 4.7, I pre-cleared two x 2TB WD green drives but (mistakenly) used -a option.

My unRAID setting is MBR-4k aligned and I realize now that I should have simply not used -a or -A on command line.

These new drives show up as MBR-unaligned, but now also contain some real data.

 

So to be anal  ;) can these drives be set to MBR 4k-aligned without re-formatting or pre-clearing again?

If not, can I simply replace drive with properly set drive (and pre-cleared [30+ hours]) and then let unRAID

rebuild that disk and re-check parity?

 

I have a third drive as MBR-unaligned that I want to use to replace a dying MBR 4k-aligned drive.

Can this currently unused drive be reset to MBR 4k-aligned, or would it have to be pre-cleared again.

 

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These new drives show up as MBR-unaligned, but now also contain some real data.

Good, then do nothing.  You'll be fine.

So to be anal  ;) can these drives be set to MBR 4k-aligned without re-formatting or pre-clearing again?

No.  Sorry, not possible
If not, can I simply replace drive with properly set drive (and pre-cleared [30+ hours]) and then let unRAID

rebuild that disk and re-check parity?

It would work, but it would leave your data un-protected for the length of time needed to do a re-construction.  Since you have a copy elsewhere, you can afford to be anal.

I have a third drive as MBR-unaligned that I want to use to replace a dying MBR 4k-aligned drive.

Can this currently unused drive be reset to MBR 4k-aligned, or would it have to be pre-cleared again.

If never assigned to the array you can use

preclear_disk.sh -C 64 /dev/sdX

to change it.  If not still in the precleared state (if you have ever assigned it to the array), this will not work.

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