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U.2 is a different kind of port, and one that's in notoriously short supply on all but the most expensive platforms. Even if you could get U.2 SSDs at the same

U.2 is a different kind of port, and one that's in notoriously short supply on all but the most expensive platforms. Even if you could get U.2 SSDs at the same price per TB as hard drives, you still need to spend a lot more to get them connected and keep them cool (enterprise SSDs don't have low-power idle states).

jeffbee 6y ago
This conversation is increasingly weird. Enterprise SSDs definitely do have low-power modes. The Samsung PM983 I've used at scale draws 4W when idle or 11W active. A 14TB Seagate HDD like the one recommended in the article draws 5W minimum. The SSDs have a 5 milliwatt non-operating mode they can exit in less than 30ms, which is dramatically better than the latency of a non-operating hard drive (and turning a hard drive off wears it out, too). The SSD wins in this regard. It's also virtually impossible to overheat an SSD. Samsung SSDs have critical temperatures above 90C. You won't reach this temperature just by operating the drive. The only way I've been able to make a Samsung SSD trip the critical temperature alarm was by pointing a paint-stripping air gun into the fan inlet of a machine while running an fio workload. HDDs by contrast are trivial to overheat, and are destroyed by doing it.
- wtallis 6y ago
  > The SSDs have a 5 milliwatt non-operating mode they can exit in less than 30ms, Which mode exactly are you referring to? Because the 983 DCTs (retail version of the PM983) that I have don't support features like NVMe APST, and idle at 3+ W (for the M.2 version, which is lower-power than the U.2 version). > It's also virtually impossible to overheat an SSD. Maybe in a properly designed rackmount enclosure with fans that never drop below 4k RPM. But in a more typical consumer case, enterprise U.2 drives will absolutely overheat, and I have the logs to prove it. (The Samsung drives you refer to are definitely better about this than the kind of U.2 drives that use 15mm thick cases and controllers with more than 8 channels—which I believe includes all U.2 drives with capacity in excess of 8TB.) Consumer cases that still have 3.5" bays tend to provide plenty of airflow for them, but that's not the case for 2.5" bays.
  - jeffbee 6y ago
    Maybe we should avoid the specifics of Samsung, since they are in the habit of shipping different firmware to retail and bulk buyers. I've never used the retail 983, and I have no experience with the u.2 either. All I can say for sure is you cannot overheat the stick version. If it overheats that's because your datacenter is on fire. I can replicate this at home with a Samsung 970 PRO m.2 in an Intel NUC. It just will not overheat. The only thing I can do to make it shut down is to put blankets over the NUC in which case the CPU has gone PROCHOT anyway. Bottom line, it seems to me that power and heat are advantages of SSD, not HDD. It seems like people buy HDD purely because of GB/$, which makes sense to me at scale but not at home. The care and management of hard drives, and their atrocious performance, seems to outweigh the price advantage. It's really hard to manage HDDs successfully and even if you are doing it perfectly, it still means you are replacing the HDD every 3-5 years. What a pain.
    - mlyle 6y ago
      > It's really hard to manage HDDs successfully and even if you are doing it perfectly, it still means you are replacing the HDD every 3-5 years. What a pain. Neither HDDs nor SSDs will last forever. It's as easy as sticking a pair of drives in a cheap NAS enclosure and listening for the warning alarm when SMART predicts failure or a drive fails. I did have to replace the previous NAS after 5 years-- not because of failure, but because I needed more storage and wanted more performance. Otherwise it might have lasted quite a bit longer.
      - jeffbee 6y ago
        An SSD that's only being read really will last ~forever. It has the same wear-out process as a CPU or RAM. A hard drive will wear out based on power-on hours and start/stop cycles, regardless of how much you use it. I'm not saying you should blindly assume that your SSD will never break, since they can and do randomly stop working, but it seems clear that reliability is a clear win for SSD over HDD, especially in consumer applications where the mere passage of time is the thing that will kill hard drives.

jeffbee 6y ago

This conversation is increasingly weird. Enterprise SSDs definitely do have low-power modes. The Samsung PM983 I've used at scale draws 4W when idle or 11W active. A 14TB Seagate HDD like the one recommended in the article draws 5W minimum. The SSDs have a 5 milliwatt non-operating mode they can exit in less than 30ms, which is dramatically better than the latency of a non-operating hard drive (and turning a hard drive off wears it out, too). The SSD wins in this regard. It's also virtually impossible to overheat an SSD. Samsung SSDs have critical temperatures above 90C. You won't reach this temperature just by operating the drive. The only way I've been able to make a Samsung SSD trip the critical temperature alarm was by pointing a paint-stripping air gun into the fan inlet of a machine while running an fio workload. HDDs by contrast are trivial to overheat, and are destroyed by doing it.

wtallis 6y ago
> The SSDs have a 5 milliwatt non-operating mode they can exit in less than 30ms, Which mode exactly are you referring to? Because the 983 DCTs (retail version of the PM983) that I have don't support features like NVMe APST, and idle at 3+ W (for the M.2 version, which is lower-power than the U.2 version). > It's also virtually impossible to overheat an SSD. Maybe in a properly designed rackmount enclosure with fans that never drop below 4k RPM. But in a more typical consumer case, enterprise U.2 drives will absolutely overheat, and I have the logs to prove it. (The Samsung drives you refer to are definitely better about this than the kind of U.2 drives that use 15mm thick cases and controllers with more than 8 channels—which I believe includes all U.2 drives with capacity in excess of 8TB.) Consumer cases that still have 3.5" bays tend to provide plenty of airflow for them, but that's not the case for 2.5" bays.
- jeffbee 6y ago
  Maybe we should avoid the specifics of Samsung, since they are in the habit of shipping different firmware to retail and bulk buyers. I've never used the retail 983, and I have no experience with the u.2 either. All I can say for sure is you cannot overheat the stick version. If it overheats that's because your datacenter is on fire. I can replicate this at home with a Samsung 970 PRO m.2 in an Intel NUC. It just will not overheat. The only thing I can do to make it shut down is to put blankets over the NUC in which case the CPU has gone PROCHOT anyway. Bottom line, it seems to me that power and heat are advantages of SSD, not HDD. It seems like people buy HDD purely because of GB/$, which makes sense to me at scale but not at home. The care and management of hard drives, and their atrocious performance, seems to outweigh the price advantage. It's really hard to manage HDDs successfully and even if you are doing it perfectly, it still means you are replacing the HDD every 3-5 years. What a pain.
  - mlyle 6y ago
    > It's really hard to manage HDDs successfully and even if you are doing it perfectly, it still means you are replacing the HDD every 3-5 years. What a pain. Neither HDDs nor SSDs will last forever. It's as easy as sticking a pair of drives in a cheap NAS enclosure and listening for the warning alarm when SMART predicts failure or a drive fails. I did have to replace the previous NAS after 5 years-- not because of failure, but because I needed more storage and wanted more performance. Otherwise it might have lasted quite a bit longer.
    - jeffbee 6y ago
      An SSD that's only being read really will last ~forever. It has the same wear-out process as a CPU or RAM. A hard drive will wear out based on power-on hours and start/stop cycles, regardless of how much you use it. I'm not saying you should blindly assume that your SSD will never break, since they can and do randomly stop working, but it seems clear that reliability is a clear win for SSD over HDD, especially in consumer applications where the mere passage of time is the thing that will kill hard drives.