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Toshiba, Seagate shipping slower SMR drives without disclosure, too

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Re: Toshiba, Seagate shipping slower SMR drives without disclosure, too

#61

Post by loeg »

seized wrote: post #46
loeg wrote: post #42

Earlier quoted context omitted.

You don't need a single Log structure -- the shingle stripes are on the order of 128 MB of or so. Any CoW filesystem can relatively easily adapt to this kind of system; in-place filesystems are basically boned on SMR. The CoW filesystem aren't going to be fast on SMR, mind you, just not quite as awful.

Except filesystems like ZFS are having issues on these SMR Reds during resilvers (rebuilds) because SMR slows down so much.

Toast0's great-grandparent comment (and my grandparent comment) are talking about Host-managed SMR, not "transparent" drive-managed SMR like these fraudulent WD Reds.

Yes, nothing except extremely low load or extremely linear (i.e., security video / tape-style backup) workflows works well with drive-managed SMR.

Re: Toshiba, Seagate shipping slower SMR drives without disclosure, too

#62

Post by cthalupa »

magicalhippo wrote: post #26
segfaultbuserr wrote: post #4

Earlier quoted context omitted.

> On the SSD side we have DRAMless and TLC. I'm happy to buy a DRAMless + TLC SSD for my boot disk on my web browsing PC (not development), it is a reasonable compromise for a lower price. Same for SMR drives, I won't have problems with them as backup disks. I think the problem here is SMR drives are sold without disclosure , and it has already created some serious problems in practice. > What’s worse, they’re shippi…

> They rebuiild (sic) for a while (1-2 hours), then throw errors and get kicked out of the set. I don't doubt it, but do you have the source for that? I read stories about people using the Seagate Archive disks in RAIDZ and it worked fine for them.

Mine completed the rebuild, but it took over 2 weeks vs. the usual 1-2 days my prior WD Red 6TBs had completed in.

This has accelerated my move to enterprise 16TB drives, because I really don't want to expose myself to data loss on rebuilds taking hugely extended times.

Re: Toshiba, Seagate shipping slower SMR drives without disclosure, too

#63

Post by cthalupa »

uluyol wrote: post #59
dragontamer wrote: post #49

Earlier quoted context omitted.

SMR is terrible for NAS setups, particularly RAID5. Absolutely terrible. Under no circumstances should you be putting an SMR drive into your NAS.

Isn't this a question of throughput? What is the bandwidth of SMR and what workloads can't it support that PMR can? I primarily use my NAS for backups and don't care too much about how slow they are, they finish quickly enough.

Try to do a resilver with SMR drives.

I just got fucked by this change in models - I had an array full of 6TB WD Reds, had one fail, ordered a replacement. Rebuilding the RAID-Z3 took over 2 weeks. Previous replacements had taken under 2 days - usually under 1.

Passing SMR drives off without saying anything, especially when that exact model had been a PMR drive prior, is incredibly anti-customer.

Re: Toshiba, Seagate shipping slower SMR drives without disclosure, too

#64

Post by gmanley »

dragontamer wrote: post #44
canada_dry wrote: post #24

Adding to this confusing debacle is how HDDs are now being marketed like running shoes: one type for running, one for squash, one for tennis, one for basketball...

There are only maybe... 3 or 4 elements of HDD designs worth talking about. * CMR/PMR drives -- Classic hard drive you've been buying for the last 30 years. Not much to say about it. * SMR Drives -- "Shingled" has very poor write performance, but adds 20% more capacity at lower costs. For "write once, read many" workloads, like archival or backups. This is because "Shingled" drives write data on top of the old data,…

I just wanted to add that SMR drives' performance is a bit more nuanced than you described. In most SMR drives, there is a PMR portion allocated as a cache. I've read the cache is usually in the range of 20-50G, depending on the size of the drive, but I'd love to know how accurate that is. So write performance is generally pretty good until you saturate that cache. Then, as you said, it becomes pretty atrocious.

Re: Toshiba, Seagate shipping slower SMR drives without disclosure, too

#65

Post by LeifCarrotson »

ubercow13 wrote: post #27
magicalhippo wrote: post #25

Earlier quoted context omitted.

A small-scale NAS implies home usage, which again implies plenty of idle time. With plenty of idle time, the SMR drive should perform decent enough, as the drive has enough time to shuffle stuff between the persistent cache region and the SMR region. Or at least that's the theory.

They have problems being chucked out of pools when resilvering, ie. when added to the pool, so the general usage pattern isn't so much the issue as is the way the filesystem or RAID controller reacts to them. In particular I think people have had problems with ZFS because the resilvering process involves a lot of random writes, and once the PMR cache on the drive is full, it will stop responding as it flushes the cac…

So we could make the build process pause until the drive resumed responding, or have the ZFS/whatever filesystem drivers recognize the difference between a dead drive and an SMR drive that's working on its cache?

I'd want the drive statistics or benchmarks to include a complete rebuild process, though.

Re: Toshiba, Seagate shipping slower SMR drives without disclosure, too

#66

Post by otterley »

cthalupa wrote: post #63
uluyol wrote: post #59

Earlier quoted context omitted.

Isn't this a question of throughput? What is the bandwidth of SMR and what workloads can't it support that PMR can? I primarily use my NAS for backups and don't care too much about how slow they are, they finish quickly enough.

Try to do a resilver with SMR drives. I just got fucked by this change in models - I had an array full of 6TB WD Reds, had one fail, ordered a replacement. Rebuilding the RAID-Z3 took over 2 weeks. Previous replacements had taken under 2 days - usually under 1. Passing SMR drives off without saying anything, especially when that exact model had been a PMR drive prior, is incredibly anti-customer.

I think the real answer here is to demand that disk manufacturers publish performance specifications. This leaves them free to change implementation details (which consumers usually don't know or care about) as long as the published specifications are accurate.

Then again, drive manufacturers are also known for changing what the definition of a unit of measurement means. Some of us remember when they arbitrarily changed the definition of a gigabyte nearly 20 years ago from 1https://www.zdnet.com/article/attention-hard-drive-manufactu...)

Re: Toshiba, Seagate shipping slower SMR drives without disclosure, too

#67

Post by otterley »

dragontamer wrote: post #48
otterley wrote: post #30

Are the disk vendors publishing performance metrics that are being violated by the use of SMR technology? Or is this just one of those cases of performance generally not being as good as it used to be, and customers becoming reliant on past behavior despite the lack of an explicit performance promise from the vendors?

> Are the disk vendors publishing performance metrics that are being violated by the use of SMR technology? Not really, no. SMR drives overlays data on top of each other, like "shingles" on a typical American roof. As such, whenever an SMR drive writes data, it must read the data "underneath" the current spot, rewrite the "underneath" data, and then lay the new data on top of it. SMR drives are great for archives (wr…

I think the real answer here is to demand that disk manufacturers publish performance specifications. This leaves them free to change implementation details (which consumers usually don't know or care about) as long as the published specifications are accurate.

Re: Toshiba, Seagate shipping slower SMR drives without disclosure, too

#68

Post by speedgoose »

jennyyang wrote: post #34
speedgoose wrote: post #16

Earlier quoted context omitted.

I do my backups in the cloud, which uses hard drives for slow storage but I couldn't care less about it. The terrible reliability and performances are not my problem anymore.

What if you lose your job and can't afford to keep paying the monthly fees, or there is corruption in your backup? You won't know until you perform a disaster recovery.

If I lose my job I get notified in advance and then I get unemployment benefits for years. It's more than enough time to find a new job before I don't have enough savings to justify cloud storage costs.

What if you connect your hard-drive and the data is corrupted or the drive isn't spinning? That did happen to me. I rather have people replacing the hard drives for me. Uploading corrupted backups to the cloud is the same than saving corrupted backups locally.

Re: Toshiba, Seagate shipping slower SMR drives without disclosure, too

#69

Post by londons_explore »

loeg wrote: post #42
toast0 wrote: post #33

Earlier quoted context omitted.

It would really be best if the drive properly identified itself, so the host os/filesystem could adapt to the drive parameters. That said, you would want to use a log structured filesystem, with a compaction feature. You want to avoid read-modify-write on the shingled areas, it's time intesive and competes with other I/O.

You don't need a single Log structure -- the shingle stripes are on the order of 128 MB of or so. Any CoW filesystem can relatively easily adapt to this kind of system; in-place filesystems are basically boned on SMR. The CoW filesystem aren't going to be fast on SMR, mind you, just not quite as awful.

I believe these SMR drives don't allow direct access to "write a block here". They try to write your writes to a staging area first, and them move them later.

The SATA/SCSI spec, together with operating systems, block device interfaces, and filesystems, would all need to be updated to have more parameters to correctly handle SMR drives properly. Since hard drives are going out of fashion and architectural changes like that will take 5+ years to be widely deployed, it's never going to happen.

Re: Toshiba, Seagate shipping slower SMR drives without disclosure, too

#70

Post by folmar »

noisem4ker wrote: post #31
rasz wrote: post #22

Earlier quoted context omitted.

Its a guaranteed 30% profit margin industry with very high patent moat. No incentives to change anything.

The article mentions thin margins and declining volume due to SSDs. I wonder where the truth lies. Anyway, I'd rather data-starve for a couple years and save up for a big SSD rather than feed those responsible for such consumer-hostile practices.

Not that SSD vendors are much better... see other comments in this post.
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