Jump to content
kimguan

Parity HDD with reallocated sectors: is this okay?

7 posts in this topic Last Reply

Recommended Posts

Posted (edited)

Hopefully, this is in the correct forum; wasn't sure if I should have posted in General Support instead.

 

My parity HDD is an Ironwolf 4TB; it survived 3 pre-clears with no errors. However, after the parity build, a notification popped up to say that the disk had 8 reallocated sectors. From reading other posts in the Forum, I understand that reallocated sectors should not be a problem unless the count begins increasing. However, that advice was always provided for data disks, not parity. The count on my parity drive has not changed since it was purchased and installed in January 2018.

 

I suppose my question is: should I do anything about the parity disk with reallocated sectors, or is it all cool unless the count starts increasing (as with data disks)? I'm wondering if it would be "safer" to swap it out for use as a data disk instead?

 

I'm about to add a second parity disk. Does this change anything with regard to any advice concerning reallocated sectors on parity disks? I'm wondering if it would be "better" if the HDD with the reallocated sectors were to be used for the second parity disk instead of the first?

 

Sorry if this is pedantic on my part, but I tend to be OCD about these things... ?

Edited by kimguan

Share this post


Link to post

If the drive was brand new in january and directly after the burn in tests showed 8 reallocated sectors then there might have been specific weak sectors not found by the factory test.

 

Note however that problematic sectors are only found by accessing all sectors of the drive. If your system does a party check every month and you haven't seen any new sectors after four parity scans then you are probably fine.

 

If I had seen a brand new drive increment reallocated sectors during the first days of use, I would probably have returned it directly instead in investing time actually using the drive and see if the counter would stay stable or continue to increment. Now the drive is a couple of months so you can't just get a brand new drive - no fun to use the warranty and get a refurbished drive in unknown state.

Share this post


Link to post
9 hours ago, kimguan said:

I'm wondering if it would be "safer" to swap it out for use as a data disk instead?

Definitely not. Parity disks are less important failure wise. If I was forced to suffer a surprise disk failure, I'd MUCH rather see a failed parity drive. There is no data directly at risk, because the parity disk doesn't hold any files. Conversely, if a data drive fails, you are at the mercy of all your other data disks + parity disk to be read perfectly to reconstruct the failed data drive.

 

Share this post


Link to post

To me, parity drives are the MOST important.  I use a WD Gold for my parity, and any old crap for the data drives.  I wouldn't be using a drive with reallocs.  No way.

Share this post


Link to post

I guess the truth is in the middle. As soon as disk recovery is required ALL other disks (parity and data) are equally important to do a complete restoral.

 

Share this post


Link to post
7 hours ago, bonienl said:

I guess the truth is in the middle. As soon as disk recovery is required ALL other disks (parity and data) are equally important to do a complete restoral.

 

 

Just that data recovery is only required if at least one data disk is dead.

With two parity disks you can have two dead parity disks and still not require any data recovery.

 

It's an advantage to use high-end drives for the parity drives, because they will have to handle more writes than any data disk which means that the total amount of work can end up being much higher on the parity disks.

 

But when it comes to failures and data security, it's always the parity disks you prefer to fail than any data disk (assuming you don't have some empty data drives where there can't be any data loss).

Share this post


Link to post
9 hours ago, HellDiverUK said:

To me, parity drives are the MOST important.

Why? If you have an array with dual parity, and you have 3 drives fail at once, which 3 drives do you hope fail first? 3 data drives? Or 2 parity and 1 data?

Share this post


Link to post

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now