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by PV Hiker on Fri Nov 30, 2018 3:45 pm
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Hi all,  I have three Synology DS1815+ NAS boxes and the main box I have the 8 bays full with 6 tb drives using raid 6.

The other two boxes are used as backups and are in raid 5.  They each have a total of 7 - 6 td drives.

The drives being used is HGST 6tb, 7200 rpm, 128mb cache, SATA 3.

My main box is reporting:

Dear user,
The bad sectors on disk 3 on DS1815+ exceeded the limit value of 1. This disk may still be working and healthy. We recommend you to make sure that your data has been properly backed up. You can also ignore or disable this value, or reconfigure it on DSM.

Additional disk information:
Brand: HGST
Model: HDN726060ALE610        
Capacity: 5.5 TB
Serial number: NAGBX6DX
Firmware: APGNT517

S.M.A.R.T. Status: Warning
Disk Reconnection Count: 0
Bad Sector Count: 24
Disk Re-identification Count: 0

I see that it is a warning and not sure how to handle this.

I have one spare hard drive that I can replace it and move on, but I need advice.

Second question:

I see that Western Digital has bought HGST and looking on the web to buy more existing drives is difficult, like B&H have them listed as discontinued.

Could I use Western Digital Red Pro WD6003FFBX 6tb 7200 rpm 256mb Cache  as a mix with the other existing drives?  Would there be a problem that the old drives are 128 mb Cache and new would be 256 mb?

Thanks for your help and advice.  Patrick
Patrick
 

by E.J. Peiker on Fri Nov 30, 2018 10:06 pm
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Pretty sure Synology says that the drives have to be identical. That doesn't mean it won't work but I would not want to put a drive with a different level of cache. That said, 3 bad sectors might not be a real issue. Perhaps run it a little while longer to see what happens while trying to find an identical replacement drive.
 

by PV Hiker on Fri Nov 30, 2018 10:30 pm
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Thanks E.J. for having a look and giving advice. Reading your comment about the cache differences, come Monday I'll try to get response direct from Synology by phone or email.

The warning it is giving me for the bad sector count is 24. You mention 3 bad sectors, is that the same? You know I don't quite understand all the techie stuff :)
Patrick
 

by Jens Peermann on Sat Dec 01, 2018 9:41 am
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PV Hiker wrote:The warning it is giving me for the bad sector count is 24.  You mention 3 bad sectors,  is that the same?  You know I don't quite understand all the techie stuff :)
A sector on a hard drive is traditionally 512 bytes. So 24 sectors will be about 12.3 kilobytes. That's not a significant number on a 6TB drive.
A great photograph is absorbed by the eyes and stored in the heart.
 

by E.J. Peiker on Sat Dec 01, 2018 10:10 am
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LOL, disk 3 - oops - my excuse, I was boarding a plane when I read this :)   Yes 24 is a lot but is it deteriorating?  Did you ever bump into the NAS - you could have had a head crash taking out 24 sectors.  If that's the reason then it's not likely to get worse.  But if it just started deteriorating then you would want to replace that drive ASAP.
 

by Jens Peermann on Sat Dec 01, 2018 11:00 am
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E.J. Peiker wrote:LOL, disk 3 - oops - my excuse, I was boarding a plane when I read this :)   Yes 24 is a lot but is it deteriorating?  Did you ever bump into the NAS - you could have had a head crash taking out 24 sectors.  If that's the reason then it's not likely to get worse.  But if it just started deteriorating then you would want to replace that drive ASAP.

How can such a small amount of sector take out such a large drive?
A great photograph is absorbed by the eyes and stored in the heart.
 

by PV Hiker on Sat Dec 01, 2018 11:58 am
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Thanks guys,

The main nas box sits on a shelf in a place where it is never touched and on a battery back up.  I do turn it off when we leave for a trip and power it back up upon return.  We returned recently and that is when the warning was received.  Would this on and off cause a shock to the drive?

Looking on the Synology web page it has the following recommendation:
Why can't I repair a volume with a new hard drive with the same capacity?
 
This usually happens when you replace the hard drive with a different brand and model. Mostly, the capacity of hard drives produced by different manufacturers differs, even though the hard drives are claimed to have the exact same capacity. We suggest replacing the hard drives either with the same brand and model or different brand and model but larger in capacity.
If I put a 8tb drive in then running raid I would have 2 tb unused, but I should be up and running.

I guess I can increase the time intervals to check the health of drive 3 and if it shows more bad sectors I can hot swap it out with a new drive.  But I do need to purchase more drive replacements.
Patrick
 

by E.J. Peiker on Sat Dec 01, 2018 1:29 pm
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It's good to know that you can go to a larger capacity. One of the reasons I use Enterprise drives in my NAS boxes is because they guarantee a certain amount of storage available not to mention some of the other designed in benefits. You would likely be OK with a RED drive of the same capacity since it is an Enterprise drive.

https://blog.storagecraft.com/consumer- ... rd-drives/
 

by PV Hiker on Sat Dec 01, 2018 1:56 pm
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I picked the red pro over the red because it matched the 7200 rpm. I did not realize that the Pro would be considered a Enterprise drive.
Patrick
 

by Royce Howland on Sun Dec 02, 2018 5:09 pm
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Synology's NAS implementation does not require that all drives be exactly matched. In particular on-board cache doesn't need to be matched; nothing outside of the drive itself can directly see the cache, it would only have some small performance differences, likely too small to be material in NAS models of this nature. Matching RPM is more important; I wouldn't run mismatched RPM drives in a single NAS.

Synology only requires that all of them have at least the same minimum amount of raw storage in order to deliver you a certain level of capacity. So if you want the equivalent of 6 TB per drive, all of them need to have at least 6 TB. The Synology help notes quoted above are correct -- not all 6 TB drives have precisely the same amount of raw storage on them, they all "plus or minus". Because you already have a bunch of matched HGST drives, that sets the smallest amount of raw storage that any replacement drive has to have. But it can have more, which is easily assured if you drop an 8 TB drive in there. It's just that the extra 2 TB won't be utilized until such time as you may upgrade the other drives as well to 8 TB or more.

Personally, I wouldn't say 24 bad sectors is worth worrying about yet, especially if they all happened at the same time. These drives have such massive storage capacities and so many built-in mechanisms for error checking, that a one-time small hit like that probably isn't meaningful. As E.J. says, the concern would come if the drive starts developing more & more bad sectors over a shorter period of time, or starts throwing a lot of other errors like persistent read retry errors or write errors, which would indicate something like the disk surface is degrading or the drive's controller is shot.

It's not impossible that the bad sectors occurred when the NAS got powered down and then back up. Power cycle is one of the highest risk times for high capacity hard drives. For that reason, I power cycle my NAS units as infrequently as possible. If I ever have any reason to believe one might be developing serious trouble, I try to back it up fully before I power it down.

I personally use WD Red drives in my 8-bay Synology boxes. Red Pro are considered Enterprise, and would be good choices as well. I find the non-Pro Reds to be reliable enough that I don't spend the extra. If I had really wanted the highest reliability of individual drives, I would have tracked down HGST drives and bought case lots of them. But as you're finding, they're hard to come by now. That's because the HGST brand no longer exists, and has been fully absorbed into the WD brand.

https://www.techrepublic.com/article/we ... t-shuffle/
Royce Howland
 

by PV Hiker on Mon Dec 03, 2018 11:32 am
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Thank you Royce for the detailed post that made it clear to understand. I do have one spare drive to use but will wait and see if the drive #3 has further reported problems then will replace the drive.

It becomes a problem that HGST replacement drives are hard to find and are being sold at a higher cost by company's that I don't want to take a chance buying when the replacement drive will sit on the shelf and used beyond the warranty claim period.

I did look at Synology online help and for hard drive compatibility for my DS1815+ list the WD Red Pro and a Seagate drives but I did not see my HGST drive in the list.

Maybe while on a two week vacation I'll leave the box powered on and running, while a longer trip will consider powering it down. It is hard to accept it will be ok to powered of while I'm not there. The drives are getting up in age and why create more shock to them.

My two 8 bay back up boxes are running raid 5 and have a empty slot. The main box is running raid 6. I'm considering adding the last drive to the raid 5 boxes and rebuilding the raid 6 to a raid 5 system. This will give us more disk size in the pool. As we have not been due diligent ruthlessly culling bad images and now we are at 80 percent capacity. We both are photographers sharing the same system.

I only question my decision going to raid 5 from a raid 6 if there will be consequences in the future?

I would have replied to you yesterday but our mail and internet computer finely crashed to the point of unusable. Costco has a Dell XPS tower on sale that I spent yesterday setting up. So far it is working nicely.

Thank you for sharing information that I need, very helpful.

Patrick
Patrick
 

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