Question Wildly Fluctuating Transfer Speeds Between SATA drives

Hello man

Honorable
So most of the forum threads I can find on the internet about this are related to USB transfer rates. Mine is not.

Basically, I have a pretty formidable system with a large amount of storage — 17TB at the moment. I’m a part time pro photographer, and about once a month or so move all my new photos from a Microsoft storage spaces RAID 1 to an 8TB archive drive. When I do this though (talking about 100+ gb of ~30mb files) I don’t get a steady transfer speed at all. It bounces between a few KB per second, then all the way up to 100mb/s and back down again at random. Basically, moving 100GB somehow ends up taking two hours, averaging maybe 20MB/S.

Since this is between SATA drives, I’m not sure what the issue is. I have seen large files copy over a network connection with more stability than this. Any ideas?
 
So most of the forum threads I can find on the internet about this are related to USB transfer rates. Mine is not.

Basically, I have a pretty formidable system with a large amount of storage — 17TB at the moment. I’m a part time pro photographer, and about once a month or so move all my new photos from a Microsoft storage spaces RAID 1 to an 8TB archive drive. When I do this though (talking about 100+ gb of ~30mb files) I don’t get a steady transfer speed at all. It bounces between a few KB per second, then all the way up to 100mb/s and back down again at random. Basically, moving 100GB somehow ends up taking two hours, averaging maybe 20MB/S.

Since this is between SATA drives, I’m not sure what the issue is. I have seen large files copy over a network connection with more stability than this. Any ideas?
It comes down to file sizes and cache in the drives, as soon as a cache fills up every transfer will slow down.
 

Hello man

Honorable
What model drives?
BTW - it's possible storage spaces are negatively impacting drive performance.
The two in redundant layout are Seagate 3TB Barracuda models. If I remember correctly, at time of purchase they weren't the cheapest 3TB Seagate available, so not like "white label system integrator" grade drives. I don't know the model no. at the moment.

The 8TB is one of Seagate's ST8000DM004 I believe.

For 30MB files it seems like transfer speeds should be pretty consistent around maybe 50MB/s, not bouncing around like mad. It seems like writing to the storage spaces drive array is fine, but maybe the use of REFS and raid 1 affected read the most?
 
It may be that one of the 3TB drives has a degraded head. Can you obtain a SMART report from each drive? Look for reallocated, pending or uncorrectable sectors. Be aware that the ST3000DM001 model had a 30% failure rate in Backblaze's servers, and it was also the subject of a law suit.
 

Hello man

Honorable
It may be that one of the 3TB drives has a degraded head. Can you obtain a SMART report from each drive? Look for reallocated, pending or uncorrectable sectors. Be aware that the ST3000DM001 model had a 30% failure rate in Backblaze's servers, and it was also the subject of a law suit.
Sheesh...I was aware Backblaze had "eh" opinion of the average Seagate drive (I work in IT) but I had NO idea that the 3TB gen 1 model had such bad failure rate. What was the outcome of the suit??

I will do a SMART scan as soon as I'm home. I might have the 007 or 008 model -- I think these drives were purchased around 2013. They have green Barracuda labels, not the blue one the 001 looks like it has.
 

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