SMR for backups / archives?

[diskdiddler]

I realise SMR is a big hated no no but it may be the only option for what I'm planning to do.

I will have a proxmox backup server VM, which writes probably 20 to 50GB a night to the intended archive location just once a night at say 2am or something.

If I had a 5 Disk (yes, I know, 5 Disk) SMR based setup, how bad would this be, on a scale of 'oh it's fine' to 'this will genuinely become a disaster' ?
I am unsure if I'll set this up with 2 redundant disks or 1, I'm still figuring that part out.

ZSTD compression will be in play, performance is not a priority to be honest as long as it can take the backup before the morning.
Any thoughts?

 

[ChrisRJ]

You are one of many people here on the forum that seem to think along the lines of "it is only a backup system, so I can be a bit more relaxed about its reliability".

To be honest, I have never been able to understand this. I mean, when do I need such a backup system? At least in my book that would be in case of a major disaster. And in such a scenario I would be anything but relaxed. In other words: My backup system must be at least as reliable as the main system.

Is there a risk that I have overlooked something in my setup? Yes. Would I consciously walk into such a situation? Not in a million years.

I am aware this does not answer your question. But to be honest, at least for me personally it is the wrong question to be begin with. Hence my "sermon". Hope it helps, nevertheless.

 

[diskdiddler]

The intention of the backup in this case is simply a second copy of something which should be working for the most part. The odds of both of them being dead is quite slim.

I understand your logic, it's more about power, space, heat, money etc. If someone sold 2TB SSDs with TLC at least, under $80 USD, I'd just switch to that, but they don't. - I can fit 6x2.5" drives in my 'spare bit' in my system (and it's a shabby install at that) so I'd like something in that space which works.

Finding a CMR 2TB 2.5" disk is nigh on impossible now, if they ever existed?

 

[ChrisRJ]

The odds of both of them being dead is quite slim.

But only if the backup system is not in your house. Otherwise the probability is actually rather high.

 

[Davvo]

The odds of both of them being dead is quite slim.

If one of them is guaranteed not to work, not quite slim: if you want to go this route, absolutely do not use WD's SMR drives since they are incompatibile with ZFS.

Finding a CMR 2TB 2.5" disk is nigh on impossible now, if they ever existed?

You only have up to 1TB in 2.5'' CMR: either take that or go SSDs; you can't spend under 80 and have CMR, larger than 1TB, and 2.5''... you have to drop one.

 

[sretalla]

If someone sold 2TB SSDs with TLC at least, under $80 USD, I'd just switch to that, but they don't.

Maybe that's getting closer to a solution... QLC drives would actually be well suited to your purpose and are probably priced near your stated range ($100 to $120).

 

[Jailer]

The biggest problem with SMR drives is they fall on their face when a scrub takes place. How do you intend to ensure that the data you are backing up is indeed secure if you don't run scrubs? And if your backup data integrity isn't verified whats' the point of doing the backup in the first place?

 

[sretalla]

QLC drives would actually be well suited to your purpose and are probably priced near your stated range ($100 to $120)

I even see some play with "less known/lower quality brands" with TLC drives in that price range.

 

[Davvo]

The biggest problem with SMR drives is they fall on their face when a scrub takes place. How do you intend to ensure that the data you are backing up is indeed secure if you don't run scrubs? And if your backup data integrity isn't verified whats' the point of doing the backup in the first place?

Actually it's the resilver that's most critical (any write intensive operation), the scrub is not an issue until you have tons of errors to correct.

 

[diskdiddler]

Ok guys you're convincing me here....

I know this is DEFINITELY not the greatest drive, but what about the "Patriot Burst Elite" SSD?
6 of those with 2 redundant?
(it sounds like a very basic drive)

[SSD] Patriot Burst Elite SATA 3 1.92TB SSD 2.5" - $91.99

Posted in r/buildapcsales by u/ligonsker • 86 points and 29 comments

old.reddit.com

I don't need wild crazy speeds, but I totally need the disks to be 2.5" unfortunately.

 

[diskdiddler]

But only if the backup system is not in your house. Otherwise the probability is actually rather high.

Yes I do realise that and it is in my list of "to do" things for the utterly critical data. I appreciate your help and being dilligent, I'm certainly not looking at this as "THE BACKUP!!!" solution for my house, at all actually, it's more "one of the faster, convienient ones" if that makes sense.

 

[diskdiddler]

Maybe that's getting closer to a solution... QLC drives would actually be well suited to your purpose and are probably priced near your stated range ($100 to $120).

Thanks for this - see my reply a few minutes ago, leaning on a DRAMLESS junker - but 6 of them with the hope they don't wildly die in 3 months (3 years would be nice)

 

[Arwen]

Actually it's the resilver that's most critical (any write intensive operation)
...

Agreed.

...
the scrub is not an issue until you have tons of errors to correct.

Except that after plenty of file churn, (deletes, then new file writes), the SMR drives will become fragmented. This slows them down, quite noticeably. Then during a supposed linear LBA, (Logical Block Addressing), walk during a Scrub, is actually quite a bit NOT linear because of the internal SMR disk's fragmentation. ZFS has no knowledge of that fragmentation.

 

[elvisimprsntr]

SMR+ZFS=Russian Roulette

You might get lucky, but then you might not.

 

[diskdiddler]

I've decided to pony up the extra and now my setup will be 6x18TB, and 6x 1.92TB (SSD)
I tend to use a lot of compression for VMs, certain types of data, since performance isn't that important for me but this will reduce writes to the SSDs too.

They're cheap and nasty, I'll update with how they go!

 

[ChrisRJ]

Just don't go for de-duplication on the VMs

 

[Davvo]

Don't go for deduplication at all until fast dedup comes out.

 

[rvassar]

The biggest problem with SMR drives is they fall on their face when a scrub takes place. How do you intend to ensure that the data you are backing up is indeed secure if you don't run scrubs? And if your backup data integrity isn't verified whats' the point of doing the backup in the first place?

No. They can fall on their face even just deleting stuff. You overflow the TRIM queue and the drives go AWOL.

(On edit: If TRIM is enabled...)

 

[Constantin]

SMR drives sold into the regular marketplace are all device-managed SMR, which is basically a SMR drive pretending to be a CMR drive, hoping that no one will notice the subterfuge. DM-SMR drives may work for a while but eventually will cause significant headaches and/or pool loss in ZFS in account of how they work.

Host-aware or host-managed SMR drives are currently solely the domain of data centers on a B2B basis. Perhaps if a big customer approached iXsystems and was willing to pay for the associated development, would HA- and HM-SMR compatibility be added to TrueNAS to limit freakouts and pool issues. I would not count on it happening, the benefits vs. costs are slim.

 

[diskdiddler]

Well, the Patriot Burst SSDs are starting to look like a problem at this point.
Copying an 80GB VHD file goes lovely, for a while, eventually dropping to horrific speeds.

https://i.imgur.com/HDilHxc.png

It varied from ada9 to ada11 just performing ghastly. Not sure what tech is in these SSDs but it ain't good.