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a large HD for TMachine backup

Z

zoran

macrumors 601
Original poster
Jun 30, 2005
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I own this old OWC enclosure. At the moment its got 3 drives on it of 2+4+4 TB. And i wish to purchase a larger HD that will work as a TMachine backup for all my drives.
The drives that will be backed up are, 1TB HD on my iMac, a 500mb external drive and the 3 drives i mentioned that are in the enclosure.
There is one empty extra hard drive space on the enclosure, that will be used for the backup drive im thinking to buy.
If its of any importance, the drives that are already used in the enclosure are WDC EFRX drives.
Any thoughts about the larger drive, what size should it be and perhaps what brand, maybe one of the same as the others?
 
Having just dealt with this, I second the above comment. Avoid SMR for Time Machine backups (that goes for incremental backups/Smart Update clones of boot drives as well). These drives can stall when there's lots of data that needs to be reassigned. That stall can prompt Time Machine to time out. You get a backup failed notice. However, and it took me a couple of years to grasp this, my data was fine and I could ignore the message and simply try again. A big however is when TM, or you, deletes a backup to create space. The rewrites are huge on SMR drives and the process can fail, or take days.

These drives are fine for large sequential reads (media) but terrible when tons of small files going both ways need to be done (torrents frequently stall & incremental backups can flag warnings).

WD is currently defending itself against a class action for not disclosing they used SMR for Network drives. In the 2.5” space I’m in, any drive 3tb or greater is almost sure to be SMR. You need to look for CMR or PMR. I ended up hauling some quite old 2tb Samsung’s out of the closet and dumped 3 of my 6 SMR drives in the trash just to regain reliable backups.

Note: HGST was bought by WD in, I believe 2012. They kept the brand alive for a while but I believe it’s now dead. Toshiba also use SMR. My gf uses a Canvio for TM and has the same isssues. Seagate as well. The 3 drives I trashed were all Seagates. Nothing but problems from the day I installed them in my bays.
 
Sorry i dont get it. Can you please tell me in a more simple way why one should not choose an SMR drive in a TimeMachine setup?
 
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You might want to see the BackBlaze disk reliability report. The differences between vendors have been greatly reduced. Interestingly I don't see any Western Digital drives in the latest report.

www.backblaze.com

Hard Drive Test Data

Hard Drive test data from the Backblaze data center. Backblaze is affordable, easy-to-use cloud storage.
www.backblaze.com www.backblaze.com
 
zoran said:
Sorry i dont get it. Can you please tell me in a more simple way why one should not choose an SMR drive in a TimeMachine setup?
Click to expand...

A: Just avoid them please.

B: On regular old spinning harddrives they write data when needed, after seeking the spot where to write.

On SMR drives they have a small segment of the disk that works like that (tens of GBs). The rest can only be written to in whole blocks (in a newer, more compact format). They first write data to the small segment, and later combine it into a new large block. If the small segment is full, the harddrive can no longer take in new data until it has written a large block. This 'stop the world' behaviour is fairly disruptive.
 
zoran said:
Sorry i dont get it. Can you please tell me in a more simple way why one should not choose an SMR drive in a TimeMachine setup?
Click to expand...
If your objective is to understand SMR, it’s not simple. I can’t put it in simple terms. If your objective is to have reliable Time Machine backups, simply avoid them. The manufacturers provide specs for their drives. Go to whatever manufacturer you’re considering and look for the acronyms SMR, CMR or PMR.
 
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In the enclosure, i must not have as a TM drive, a disk thats either SMR or CMR or PMR... is that correct?
Or should none of the drives in the enclosure be one of those?
What about the WDC EFRX drives, are they SMR, CMR, PMR?
 
Sorry, I should have expanded. You should avoid SMR. You want CMR or PMR. The latter 2 may be the same thing. I’ve see them used interchangeably.

If you are using 3.5” drives, you have a fairly easy job staying away from SMR drives. There are choices.

For anyone to help on sizing, the variables are how much total space do you want to backup? That's drive space less omitted folders/drives. Frequency of backups (default or edited)? How many iterations do you want captured? How often are large files created/changed? An example might be movies that are downloaded, viewed, deleted, replaced, and on and on. That would create a need for a lot of space. Or, skip backing up video, what I do. Only you know this stuff.
 
My original link shows that EFRX is still the classical way of storing data ("WD Red 4TB WD40EFRX (CMR)"). Those are not slow.

Avoid WD harddrives with 'EFAX' in the name. Those are SMR. Do not buy those.

If in doubt, off-the-shelf NAS manufacturers have compatibility listings that also list if it's an SMR drive (which you should avoid).

Edit: Slightly better link that lists them all.
 
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Clear this one out for me. SMR drives shouldn't be used as TMachine backup drives, or must they not be used in Enclosures as storage drives at all?
 
Ray2 said:
Sorry, I should have expanded. You should avoid SMR. You want CMR or PMR. The latter 2 may be the same thing. I’ve see them used interchangeably.

If you are using 3.5” drives, you have a fairly easy job staying away from SMR drives. There are choices.

For anyone to help on sizing, the variables are how much total space do you want to backup? That's drive space less omitted folders/drives. Frequency of backups (default or edited)? How many iterations do you want captured? How often are large files created/changed? An example might be movies that are downloaded, viewed, deleted, replaced, and on and on. That would create a need for a lot of space. Or, skip backing up video, what I do. Only you know this stuff.
Click to expand...
- Could you give me an example of CMR or PMR drives for use on a Enclosure like the one i own?
- As i said in the first post, the drives that will be backed up are almost full of data and they are: 1TB HD on my iMac, a 500mb external drive and 3 drives of 2+4+4TB (all of which are half full) and are located in the in the enclosure.
 
It is fairly easy:

You go to a webshop and think "Hmm, I want to buy this one". Then you figure out if it is an 'SMR' drive. If it is: you don't buy it, but buy another one.
 
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If SMRs have such an issue, how come they aren't discontinued or see on the press some kind apology from WD, or some press conference where WD offers some kind of customer compensation?
 
They thought they could get away with it, in low performance requirements environments. If you only ever slowly fill it with data, you'll never notice.

Now they hope they still can get away with it. Since they certainly don't want to do a costly recall.
 
So where can WD users can append to regarding this issue?
Henk Poley said:
They thought they could get away with it, in low performance requirements environments. If you only ever slowly fill it with data, you'll never notice.
Now they hope they still can get away with it. Since they certainly don't want to do a costly recall.
Click to expand...
What do u mean by saying "they thought they could get away with it" and "now they hope..."? Do you something related regarding this?
 
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Henk Poley said:
Anything that is not SMR: https://www.servethehome.com/wd-red-smr-vs-cmr-tested-avoid-red-smr/

Toshiba/HGST are famously reliable: https://www.backblaze.com/blog/backblaze-hard-drive-stats-q1-2020/

But more expensive, and if you use RAID with a parity drive, a drive failure is not necessarily a problem. Also HGST is now owned by Western Digital, so you would have to look around which are their designed drives under the WD brand.
Click to expand...
Thanks you man! I was about to buy a WD RED when I saw your post. What finally allowed me to discover the scandal of SMR hard drives! I didn't know anything about it.
 
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Ray2 said:
Having just dealt with this, I second the above comment. Avoid SMR for Time Machine backups (that goes for incremental backups/Smart Update clones of boot drives as well). These drives can stall when there's lots of data that needs to be reassigned. That stall can prompt Time Machine to time out. You get a backup failed notice. However, and it took me a couple of years to grasp this, my data was fine and I could ignore the message and simply try again. A big however is when TM, or you, deletes a backup to create space. The rewrites are huge on SMR drives and the process can fail, or take days.

These drives are fine for large sequential reads (media) but terrible when tons of small files going both ways need to be done (torrents frequently stall & incremental backups can flag warnings).

WD is currently defending itself against a class action for not disclosing they used SMR for Network drives. In the 2.5” space I’m in, any drive 3tb or greater is almost sure to be SMR. You need to look for CMR or PMR. I ended up hauling some quite old 2tb Samsung’s out of the closet and dumped 3 of my 6 SMR drives in the trash just to regain reliable backups.

Note: HGST was bought by WD in, I believe 2012. They kept the brand alive for a while but I believe it’s now dead. Toshiba also use SMR. My gf uses a Canvio for TM and has the same isssues. Seagate as well. The 3 drives I trashed were all Seagates. Nothing but problems from the day I installed them in my bays.
Click to expand...
Hmm very interesting! This is exactly what happened 2 days ago with my LaCie d2 Quadra that I use for TimeMachine. TimeMachine reported an error "not enough place to save" while normally it automatically deletes older backups... Since then the hard drive does not work anymore: "can't read the hard drive anymore". If I hadn't made a backup of my backup I would lose all my work files...

Inside the LaCie it's a Seagate Barracuda: st2000dm001 (bought on january 2014... Not used a lot maybe a hundred times On/off to make a save with TM).
 
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