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what's behind the infamous Seagate BSY bug?

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DiTBho:
What I have vaguely understood:


* CMR, Conventional Magnetic Recording
* SMR, Shingled Magnetic Recording
I know that if the drive has a lower cache, like 64MB, it is most likely an SMR drive, and to be honest, there are not that many drives that are being manufactured as SMR. At least, I can only count a few.


* SMR
Pros Of An SMR Hard Drive
Cheaper
good choice if they are used mostly for just data storage
good for archiving tasks
provide more storage capacity
more energy-efficient

Cons Of An SMR Hard Drive
not particularly well suited if the drive is meant to be constantly and permanently performing writing operations as that can result in a cache overflow
Slow Transfer

* CMR
Pros Of An CMR Hard Drive
good choice when data is intended to be stored at high transfer rates
good choice when extremely large amounts of data is intended to be stored
activities ranging from music streaming, audio, video, image processing

Cons Of An CMR Hard Drive
not made for NAS servers


--- Quote from: hans on May 01, 2022, 09:48:37 am ---swapping CMR for SMR technology, which is the last thing you need in a RAID array once a disk eventually fails

--- End quote ---

can you explain this point?  :-//

DiTBho:

--- Quote from: madires on May 01, 2022, 12:10:06 pm ---They seem to have a lucky hand in making turd drives.

--- End quote ---


"smile so as not to cry"
I think they should put a sticker like this on the top of their HDs.

or T-shirts?  :o :o :o

hans:

--- Quote from: DiTBho on May 01, 2022, 12:20:43 pm ---
--- Quote from: hans on May 01, 2022, 09:48:37 am ---swapping CMR for SMR technology, which is the last thing you need in a RAID array once a disk eventually fails

--- End quote ---

can you explain this point?  :-//

--- End quote ---

CMR/SMR in essence has little to do with "NAS operation". CMR drives have been made for 24/7 operation for centuries, including NAS. SMR is a relatively new tech in which magnetic tracks are recorded so closely together, that you can't write 1 without affecting the others. Therefore in order to effectively write new data to a track, the disk needs to read nearby data and encode it accordingly. This means that a SMR drive may have good write speeds whilst unformatted, but when it gets fuller it gets slower and slower.. eventually dropping to rubbish USB 2.0 thumb drive speeds. These disks are horrible for write-heavy workloads.

For many applications, this is not all bad. If your NAS is full of large video files which you never overwrite or delete, then you'll be happy with the extra capacity/$. However, if you're in a NAS environment, then it's likely to be running a RAID setup. That means that WHEN a disk fails, it will need to be replaced, and a full disk read/write needs to take place to rebuild from the parity data. It turns out that this is incredibly slow on SMR drives, like an order of magnitude slower. While the RAID array is rebuilding, it is less or completely unprotected against any further disk failures. And how much can go wrong in 1 week instead of half a day rebuild?
Well, your guess is as good as mine! But all I know is that if a light bulb in my car fails and I go to the garage to replace it, then I will also replace the bulb of the other side, since it has the same amount of running time and 'wear'. That old bulb might fail on the trip back home, or 3 years down the line, who knows. But I wouldn't feel very comfortable with the array running in that state for a very long time.

CJay:
Lots of Seagate bashing but WD are pretty awful, the most regular data loss I've encountered has been on WD drives being unable to read firmware from the platters, then there's the infamous IBM/Hitachi Deathstar drives and then the Fujitsu Hybrid drives which corrupt filesystems at random and etc. etc. etc.

Point being, all hard drives have failure modes, at least the Seagate BSY one could be 'fixed' via the serial console, you're shit out of luck if your WD drive fails to read its firmware and the less said about the Deathstars the better.

DiTBho:
So, SMR as data storage, CMR for recurring write processes.

And it's not so easy because both technologies SMR and CMR have their justification and their respective fields of application, with benefits and issues

I am looking at

* the Seagate IronWolf is a 4TB CMR NAS HDD.
* the WD Red Plus WD60EFRX-CMR is a 6TB CMR NAS HDD.
meanwhile I have just ordered qty=16 Fujitsu Maw-Enterprise uwide-320 SCSI disks. Only 72GB of storage, four disks are something like 500GB, so less than what you can store in a common low-end sATA disc, but their specs look impressive and I paid only 20 euro each, old-new-stock, and this way I don't need to provide my customers any sATA-to-SCSI box for adapting disks, only a super simple 8x SCSI bay, two boxes, 8x bays each, connect each to a dedicated SCSI chain.

I hope these 2008 disks are worth the money, I bought the entire stock, physically the entire cargo of SCSI disks in a remote warehouse (add 60 euro for UPS, but thanks god, no importing fee).

Right, I will think again about the sATA SMR disks ... I also need something modern for editing and storing videos, and I am completely new to this.

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