5 ms·

> WD make special SKUs for security camera use The workload for a security camera or a DVR is going to be pretty different from a lot of NAS devices or desktop

> WD make special SKUs for security camera use The workload for a security camera or a DVR is going to be pretty different from a lot of NAS devices or desktop/server use. Shingled Magnetic Recording (SMR) is fine for things like a security camera, where you're just going to be writing long files and probably just overwrite eventually. SMR is really bad if you need lots of random sparse file modifications. I do agree they're probably overboard on SKUs but having an obvious SMR SKU versus non-SMR is pretty important in my book. The fact they mixed in SMR into some regular drives and muddied the waters on which tech is going into which SKU really turned me off WD; I don't think I'll ever buy another one of their hard drives again.

lmpdev 2y ago
Yes PSA to anyone reading: do not use Purple drives for anything non-DVR/NVR related
- duskwuff 2y ago
  Is there something that makes them unsuitable for other workloads?
  - smegsicle 2y ago
    write amplification. random writes can take, what twice as long? wear leveling could mitigate, but the choices are somewhat limited: NILFS seems to make assumptions based on SSDs, blowing up during its cleaning operation btrfs or bcachefs could help, but who knows whats going on with those
    - buran77 2y ago
      WD mixed both CMR and SMR for the WD Purple, an a few other models too. The CMR wouldn't see any write amplification. But the SMR will suffer from all of the usual SMR limitations. Most importantly that it's only really useful with sequential writes, on top of the write amplification. Actually the Purple only has one distinguishing characteristic. An ATA command to skip bad sectors instead of trying to read/write repeatedly. This is great for an NVR but it's not mandatory to use.
      - scottlamb 2y ago
        > WD mixed both CMR and SMR for the WD Purple, an a few other models too. Could you point me at an example of a SMR-based WD Purple drive? Is this just a historical thing? As mentioned in my other comment, the spec sheets [1] say all (current) drives are CMR. > Actually the Purple only has one distinguishing characteristic. An ATA command to skip bad sectors instead of trying to read/write repeatedly. This is great for an NVR but it's not mandatory to use. I'd also be interested to see a reference / details for this. [1] https://products.wdc.com/library/SpecSheet/ENG/product-brief-wd-purple-hdd.pdf https://products.wdc.com/library/SpecSheet/ENG/product-brief... https://products.wdc.com/library/SpecSheet/ENG/product-brief-wd-purple-pro-sata-hdd.pdf https://products.wdc.com/library/SpecSheet/ENG/product-brief...
      - Dalewyn 2y ago
        >WD mixed both CMR and SMR I was a fan of WD HDDs before and I was in the market for some drives for my new NAS a few years ago. When I checked what drives were on the market, I saw WD doing that while Seagate still clearly marked which drives were which. I swore off WD that day because my time is too valuable for their bullshit. I have no clue if they have amended their marketing, but I don't care since as far as I'm aware Seagate still clearly marks them and the drives I bought from them have all been fine. I'll likely buy Seagate again next time I'm in the market.
    - snvzz 2y ago
      >NILFS seems to make assumptions based on SSDs, blowing up during its cleaning operation Wait what? Isn't NILFS designed for spinning rust?
PaulHoule 2y ago
The odd thing is that SMR may actually improve performance for many mainstream workloads because it turns random access writes to sequential writes. Similar techniques are used in software for write-heavy workloads (e.g. cache helps with reads more than writes, only helps with writes if they are battery backed and it can help a lot of if writes are sequentialized) This is why WD figured they could get away with it, but it's a shame what it does if you're rebuilding your ZFS array (if they'd actually talked to customers they might have find a lot of people who buy big drives are ZFS heads!) Myself I had a security camera set up to monitor my "cat room" last summer when I was trying to gentle a feral cat, I am thinking of pointing it at the driveway and monitoring it with ZoneMinder. ZoneMinder wants its own volume to write to, I am thinking of putting in a spare Intel SSD (superior, though review sites never told you) for that purpose, it's not like I need to store terabytes worth of video from it.
- magicalhippo 2y ago
  There was an early SMR talk by a WD (IIRC) engineer to a crowd of ZFS devs and sysadmins, and the engineer thought it should fit well because he misheard the default record size being 128MB rather than the actual 128kB, so thought it one record would fit one zone.
  - Dylan16807 2y ago
    That seems like a pretty big mistake, are you sure that's real? ZFS has a lot of genuine potential to work well with SMR drives, but that potential depends on glue code that nobody has written yet. I think BTRFS is halfway there?
    - scottlamb 2y ago
      > ZFS has a lot of genuine potential to work well with SMR drives, but that potential depends on glue code that nobody has written yet. ...and I'm not sure that will change. The thing is, the "drive-managed SMR" models I've managed to get my hands on don't have a zoned storage API. I'm not sure how a filesystem (or application that directly goes to the block device layer) is supposed to work with them intelligently. There are supposed to be host-managed and hybrid host+drive-managed SMR drives out there, but AFAICT they're only sold to enterprises/hyperscalers (maybe only the latter even). And those are using custom proprietary software (e.g. Google's D servers). ...so who would write/use this glue code? unless the manufacturers decide to contract filesystem developers as a lead-up to wider sale of these things, or something to that effect.
throwaway48476 2y ago
DMSMR is TERRIBLE for a DVR workload. It writes first to a CMR cache and then flushes to SMR when the drive isn't busy. With a DVR the drive is never not going to be busy. Further the pitiful write speed of SMR is likely not enough for a modern high resolution security camera installation.
- yencabulator 2y ago
  At least for some brands/models, a workload of purely sequential large writes doesn't exhibit that slowdown -- so I'm assuming they go straight to an open SMR zone. There might be an extra criteria where the rate of writes has be just below some threshold so the drive has time to seal full zone & open up a new one in time, to avoid CMR buffering.
scottlamb 2y ago
> The workload for a security camera or a DVR is going to be pretty different from a lot of NAS devices or desktop/server use. Shingled Magnetic Recording (SMR) is fine for things like a security camera, where you're just going to be writing long files and probably just overwrite eventually. SMR is really bad if you need lots of random sparse file modifications. In theory you're right, SMR is not necessarily a problem for NVRs if well-implemented. However, I had poor luck running my own NVR software on drive-managed SMR. (The cheap kind that doesn't support zoned storage APIs, just pretends to be a standard drive.) 2/2 drives failed within a year, despite staying within the rated workload. Admittedly it's a small sample, but it soured me on drive-managed SMR. I suspect NVR software written to use host-managed SMR or hybrid SMR might have better luck, but AFAICT those drives are only sold to enterprises. ...and AFAICT, the WD Purple Surveillance Hard Drive and WD Purple Pro Smart Video Hard Drive lines do not use SMR. Looking at the current highest-capacity drives for both lines: * The WD Purple Surveillance Hard Drive, 8TB (WD11PURZ) is specced at 180TB/yr. * The WD Purple Pro Smart Video Hard Drive, 24TB (WD240PURP) is specced at 550TB/yr. ...vs something like 55 TB/yr that I've seen for SMR drives. https://nascompares.com/answer/list-of-wd-cmr-and-smr-hard-drives-hdd/ https://nascompares.com/answer/list-of-wd-cmr-and-smr-hard-d... also says that WD11PURZ is CMR. No listing for WD240PURP. edit: oh, and the spec sheets for both lines explicitly say all drives use CMR. https://products.wdc.com/library/SpecSheet/ENG/product-brief-wd-purple-hdd.pdf https://products.wdc.com/library/SpecSheet/ENG/product-brief... https://products.wdc.com/library/SpecSheet/ENG/product-brief-wd-purple-pro-sata-hdd.pdf https://products.wdc.com/library/SpecSheet/ENG/product-brief...
juancn 2y ago
SMR is discouraged for DVR use, many vendors (e.g. Ubiquiti) specifically ask for CMR drives.

lmpdev 2y ago

Yes PSA to anyone reading: do not use Purple drives for anything non-DVR/NVR related

duskwuff 2y ago
Is there something that makes them unsuitable for other workloads?
- smegsicle 2y ago
  write amplification. random writes can take, what twice as long? wear leveling could mitigate, but the choices are somewhat limited: NILFS seems to make assumptions based on SSDs, blowing up during its cleaning operation btrfs or bcachefs could help, but who knows whats going on with those
  - buran77 2y ago
    WD mixed both CMR and SMR for the WD Purple, an a few other models too. The CMR wouldn't see any write amplification. But the SMR will suffer from all of the usual SMR limitations. Most importantly that it's only really useful with sequential writes, on top of the write amplification. Actually the Purple only has one distinguishing characteristic. An ATA command to skip bad sectors instead of trying to read/write repeatedly. This is great for an NVR but it's not mandatory to use.
    - scottlamb 2y ago
      > WD mixed both CMR and SMR for the WD Purple, an a few other models too. Could you point me at an example of a SMR-based WD Purple drive? Is this just a historical thing? As mentioned in my other comment, the spec sheets [1] say all (current) drives are CMR. > Actually the Purple only has one distinguishing characteristic. An ATA command to skip bad sectors instead of trying to read/write repeatedly. This is great for an NVR but it's not mandatory to use. I'd also be interested to see a reference / details for this. [1] https://products.wdc.com/library/SpecSheet/ENG/product-brief-wd-purple-hdd.pdf https://products.wdc.com/library/SpecSheet/ENG/product-brief... https://products.wdc.com/library/SpecSheet/ENG/product-brief-wd-purple-pro-sata-hdd.pdf https://products.wdc.com/library/SpecSheet/ENG/product-brief...
    - Dalewyn 2y ago
      >WD mixed both CMR and SMR I was a fan of WD HDDs before and I was in the market for some drives for my new NAS a few years ago. When I checked what drives were on the market, I saw WD doing that while Seagate still clearly marked which drives were which. I swore off WD that day because my time is too valuable for their bullshit. I have no clue if they have amended their marketing, but I don't care since as far as I'm aware Seagate still clearly marks them and the drives I bought from them have all been fine. I'll likely buy Seagate again next time I'm in the market.
  - snvzz 2y ago
    >NILFS seems to make assumptions based on SSDs, blowing up during its cleaning operation Wait what? Isn't NILFS designed for spinning rust?

PaulHoule 2y ago

The odd thing is that SMR may actually improve performance for many mainstream workloads because it turns random access writes to sequential writes. Similar techniques are used in software for write-heavy workloads (e.g. cache helps with reads more than writes, only helps with writes if they are battery backed and it can help a lot of if writes are sequentialized) This is why WD figured they could get away with it, but it's a shame what it does if you're rebuilding your ZFS array (if they'd actually talked to customers they might have find a lot of people who buy big drives are ZFS heads!) Myself I had a security camera set up to monitor my "cat room" last summer when I was trying to gentle a feral cat, I am thinking of pointing it at the driveway and monitoring it with ZoneMinder. ZoneMinder wants its own volume to write to, I am thinking of putting in a spare Intel SSD (superior, though review sites never told you) for that purpose, it's not like I need to store terabytes worth of video from it.

magicalhippo 2y ago
There was an early SMR talk by a WD (IIRC) engineer to a crowd of ZFS devs and sysadmins, and the engineer thought it should fit well because he misheard the default record size being 128MB rather than the actual 128kB, so thought it one record would fit one zone.
- Dylan16807 2y ago
  That seems like a pretty big mistake, are you sure that's real? ZFS has a lot of genuine potential to work well with SMR drives, but that potential depends on glue code that nobody has written yet. I think BTRFS is halfway there?
  - scottlamb 2y ago
    > ZFS has a lot of genuine potential to work well with SMR drives, but that potential depends on glue code that nobody has written yet. ...and I'm not sure that will change. The thing is, the "drive-managed SMR" models I've managed to get my hands on don't have a zoned storage API. I'm not sure how a filesystem (or application that directly goes to the block device layer) is supposed to work with them intelligently. There are supposed to be host-managed and hybrid host+drive-managed SMR drives out there, but AFAICT they're only sold to enterprises/hyperscalers (maybe only the latter even). And those are using custom proprietary software (e.g. Google's D servers). ...so who would write/use this glue code? unless the manufacturers decide to contract filesystem developers as a lead-up to wider sale of these things, or something to that effect.

throwaway48476 2y ago

DMSMR is TERRIBLE for a DVR workload. It writes first to a CMR cache and then flushes to SMR when the drive isn't busy. With a DVR the drive is never not going to be busy. Further the pitiful write speed of SMR is likely not enough for a modern high resolution security camera installation.

yencabulator 2y ago
At least for some brands/models, a workload of purely sequential large writes doesn't exhibit that slowdown -- so I'm assuming they go straight to an open SMR zone. There might be an extra criteria where the rate of writes has be just below some threshold so the drive has time to seal full zone & open up a new one in time, to avoid CMR buffering.

scottlamb 2y ago

> The workload for a security camera or a DVR is going to be pretty different from a lot of NAS devices or desktop/server use. Shingled Magnetic Recording (SMR) is fine for things like a security camera, where you're just going to be writing long files and probably just overwrite eventually. SMR is really bad if you need lots of random sparse file modifications. In theory you're right, SMR is not necessarily a problem for NVRs if well-implemented. However, I had poor luck running my own NVR software on drive-managed SMR. (The cheap kind that doesn't support zoned storage APIs, just pretends to be a standard drive.) 2/2 drives failed within a year, despite staying within the rated workload. Admittedly it's a small sample, but it soured me on drive-managed SMR. I suspect NVR software written to use host-managed SMR or hybrid SMR might have better luck, but AFAICT those drives are only sold to enterprises. ...and AFAICT, the WD Purple Surveillance Hard Drive and WD Purple Pro Smart Video Hard Drive lines do not use SMR. Looking at the current highest-capacity drives for both lines: * The WD Purple Surveillance Hard Drive, 8TB (WD11PURZ) is specced at 180TB/yr. * The WD Purple Pro Smart Video Hard Drive, 24TB (WD240PURP) is specced at 550TB/yr. ...vs something like 55 TB/yr that I've seen for SMR drives. https://nascompares.com/answer/list-of-wd-cmr-and-smr-hard-drives-hdd/ https://nascompares.com/answer/list-of-wd-cmr-and-smr-hard-d... also says that WD11PURZ is CMR. No listing for WD240PURP. edit: oh, and the spec sheets for both lines explicitly say all drives use CMR. https://products.wdc.com/library/SpecSheet/ENG/product-brief-wd-purple-hdd.pdf https://products.wdc.com/library/SpecSheet/ENG/product-brief... https://products.wdc.com/library/SpecSheet/ENG/product-brief-wd-purple-pro-sata-hdd.pdf https://products.wdc.com/library/SpecSheet/ENG/product-brief...

juancn 2y ago

SMR is discouraged for DVR use, many vendors (e.g. Ubiquiti) specifically ask for CMR drives.