[SOLVED] Looking for a 4TB Desktop 3.5" External HD that is PMR, not SMR.

[red pine]

I am looking for an external HD I can use for backups on a new 27" iMac The problem is that all the drives I've looked into do not specify whether they are PMR or SMR? Even OWC could not tell me what's in their own Mercury Elite Pro external HDs? Does anyone here know of a 4TB desktop external drive that is PMR? Thanks.

 

[popatim]

Probably none at this point since they are cheaper to make. I think you'll need to make your own external.

 

[hbutty]

I am looking for an external HD I can use for backups on a new 27" iMac The problem is that all the drives I've looked into do not specify whether they are PMR or SMR? Even OWC could not tell me what's in their own Mercury Elite Pro external HDs? Does anyone here know of a 4TB desktop external drive that is PMR? Thanks.

Home

The Importance of Resiliency and Cluster Management in ROBO HCI September 28, 2020 0

forums.storagereview.com

 

[red pine]

Probably none at this point since they are cheaper to make. I think you'll need to make your own external.

What someone far more knowledgeable than me had to say on this topic:

"For most 3.5" drives up to 4TB, SMR is not worth it. It is used for 6TB and 8TB more often and seldom seems used for the even larger drives. For laptop drives, 2.5", any above 4TB could be SMR."

Any validity to this general observation?

The little bit of time I've spent looking into making my own, I run into the same issue: none so far are delineated as either SMR or PMR?

Can a NAS external work for my backups assuming I could find one I knew was PMR? I heard that the 4TB WD Red NAS drives are likely PMRs.

 

[fzabkar]

All SMR drives use PMR technology. Instead you should be comparing SMR with CMR.

 

[red pine]

All SMR drives use PMR technology. Instead you should be comparing SMR with CMR.

Yes, I ran across this distinction somewhere over the last few days. Thanks for the heads-up. I will see what I come up with when Googling CMR vs. SMR.

 

[mundial]

Even, if your disk does use SMR, most SMR technology used in hard disk production now is 2nd generation which is actually not that bad.

(Yes, the 1st iteration of SMR was a mess, I admit that!)

 

[fzabkar]

SMR drives seem to require larger cache, typically 256MB. That's one potential clue in those cases where the drive isn't explicitly identified as SMR or CMR. SMR drives also seem to require power loss data protection, whereas CMR drives don't appear to have this feature. I wouldn't consider these to be hard and fast rules, though.

 

[popatim]

What someone far more knowledgeable than me had to say on this topic:

"For most 3.5" drives up to 4TB, SMR is not worth it. It is used for 6TB and 8TB more often and seldom seems used for the even larger drives. For laptop drives, 2.5", any above 4TB could be SMR."

I'll disagree with that; there are 2TB SMR drives on the market and have been for a while.
A 4tb SMR drive using two 2TB platters and 4 heads I would think is cheaper to make then the classic four 1tb platters with 8 heads considering it all fits into the same housing & cover. It may even use the same or similar controller board with just different firmware or fzabkar could probably tell it was SMR just by looking at that. LoL

SMR drives absolutely have to be cheaper to make otherwise they would be more expensive and nobody would market them; right?

 

[red pine]

Even, if your disk does use SMR, most SMR technology used in hard disk production now is 2nd generation which is actually not that bad.

(Yes, the 1st iteration of SMR was a mess, I admit that!)

I would be very interested in knowing more about when that 2nd generation hit the market and what specific improvements were made to them? I haven't seen anything on this at all and it could have quite an impact on those who think these SMR drives are problematic.

 

[popatim]

It's not that they are problematic, it's that they can be. They have slowdowns if data needs to be rewritten in sectors that have adjacent tracks already filled also.

Like an SSD cannot change a cell without rewriting the entire page, SMR cannot rewrite a sector without rewriting entire tracks due to the write head being much bigger then the read head. Say the write head is size 1 width, it lays down the 1st track, moves up only a 1/2 width and lays down the next one, and so on. The read head can read the 1/2 width track fine but the write head cannot make a change within those tracks without overwriting the 1/2 track above it, and so on up the chain of tracks.

So they are fine for data that doesn't change much or only has new data added, but for constantly changing data - not so good if you need performance from it.

For my servers music, documents, photo, and video archives they would be fine. My TV Recordings drive though would probably be a different story.

 

[red pine]

It's not that they are problematic, it's that they can be. They have slowdowns if data needs to be rewritten in sectors that have adjacent tracks already filled also.

Like an SSD cannot change a cell without rewriting the entire page, SMR cannot rewrite a sector without rewriting entire tracks due to the write head being much bigger then the read head. Say the write head is size 1 width, it lays down the 1st track, moves up only a 1/2 width and lays down the next one, and so on. The read head can read the 1/2 width track fine but the write head cannot make a change within those tracks without overwriting the 1/2 track above it, and so on up the chain of tracks.

So they are fine for data that doesn't change much or only has new data added, but for constantly changing data - not so good if you need performance from it.

For my servers music, documents, photo, and video archives they would be fine. My TV Recordings drive though would probably be a different story.

 

[red pine]

Well articulated description of why these drives can be problematic. Thank you.

I do have something bordering on contempt for why these manufacturers simply refuse to disclose what sort of drive they’re selling you? They should proclaim in LARGE TEXT FONT.. I am archive drive suitable for long term data storage only. Never to be written over.. ie like the DVD write once or worm drives.. write once read many times.