Troubleshoot slow performance RAIDz2

Chris Moore

Hall of Famer
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May 2, 2015
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After replacing the drive that is acting up I'd retest the speed of the vdev both your old and new Seagates supposedly use the same recording technology. Which Seagate is pointedly avoiding calling SMR.....

Manuals
ST4000DM000, ST4000DM004
You have misunderstood the information presented. The ST4000DM000 drives are not SMR drives and are working properly. The ST4000DM004 are SMR drives and are running slower than the other. The ST4000DM005 drive presented bad sectors and is probably behaving badly because of that.

I will do some testing, but it will need to wait for a while. Other priorities.


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Joined
Jan 18, 2017
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You're right I missed the 005 part but it makes little difference according to Seagte none of your drives are PMR
 
Joined
May 10, 2017
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according to Seagte none of your drives are PMR

Seagate is very inconsistent in how they identify the recording technology in their drives, like discussed above, where an earlier manual revision had "Perpendicular recording technology" that a latter revision expanded to "Shingled magnetic recording with perpendicular magnetic recording heads/media.", they are not lying when they just say the former, since shingled still uses perpendicular technology, with shingled magnetic recording on top, they just don't mention SMR sometimes, likely on purpose due to the bad performance connotations associtated with SMR.

ST4000DM000/005 are PMR, ST4000DM004 is SMR.
 

Apollo

Wizard
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Jun 13, 2013
Messages
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I am using the Archive version of the Seagate drives, for archiving purposes and I do a lot of replication to them. When they work they work well and can easily reach 180MB/s throuhgput per drive (from what I can recall). I did however have a bad drive slowing everything down, but couldn't say it was bad out of the box. Instead, I noticed a consistent steady 100% busy on a single drive out of RAIDZ1 (3 disks volume).
 

Chris Moore

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I did however have a bad drive slowing everything down, but couldn't say it was bad out of the box. Instead, I noticed a consistent steady 100%
The ST4000DM005 drive that presented bad sectors for me got up to 1920 bad sectors and 6 ATA errors before I pulled the drive. I have resilvered in three of the four spares I had on hand and the pool is performing much closer to anticipated levels. I might have time to do some testing next weekend, but I have a lot of other things pulling me away from this for now.
The replacement drives are Seagate Constellation ST4000NM0033-9ZM.
They have different characteristics than the rest of the drives in the pool, but it is what I had handy.
 

konetzed

Dabbler
Joined
Aug 16, 2018
Messages
20
I wanted to add this to this thread.

I fell victim to the ST4000DM004 drives recently when I had an ST4000DM000 fail after 5 years of service. Amazon recommended it as a new drive and after reading a few reviews and some quick searches I figured it would be a good replacement. After adding the ST4000DM004 my FreeNAS box started to rebuild the array as expected but the resilver was really slow like it said it would take 4 days. I was taking off for the weekend so I figured the time was just off and it would be done way before I got home. Three days later when I got home the array was still only at 20% done and the nfs server was acting really funny. Every now and then the nfs server would just stop responding for about 30 seconds. I replaced cables, reseated all the drives, checked ram and procs but nothing would fix the issue. After a lot of searching, I found this thread and then knowing what to look for I found a few more. Eventually, I decided to test if it was the new drive and yanked it out of the box. As soon as I did all issues were resolved and the box has been working flawlessly since. Sad to see that Seagate switched up drives like this in a line that I used to use a lot.
 
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