4 ms·

I hoped it would discuss how SSDs cope with sudden power loss, but it doesn't seem to. I remember this page but I don't know of a modern update: http://lkcl.ne

I hoped it would discuss how SSDs cope with sudden power loss, but it doesn't seem to. I remember this page but I don't know of a modern update: http://lkcl.net/reports/ssd_analysis.html http://lkcl.net/reports/ssd_analysis.html These days, if I want an SSD for my desktop and want to minimise the chance I have a disk problem and have to restore from backup, would I be better off with one "data centre" drive (eg Intel D3-S4510), or two mirrored "consumer" drives (perhaps from two different manufacturers)? The prices look similar either way.

bb88 7y ago
The big problem with one data center drive is that if that goes bad, you still lose all your data. You're assuming their marketing MTBF is correct. They do make NVME raid solutions now -- with the advantage being that NVME can be faster than SATA. And there are various price points for the NVME drives depending upon speed. This one from 2018 (not sure if it has full raid or uses VROC)(EDIT: it requires software raid) https://www.pcworld.com/article/3297970/highpoint-7101a-pcie-nvme-raid-card-review.html https://www.pcworld.com/article/3297970/highpoint-7101a-pcie... This one is cheaper but relies upon Intel VROC (which has been hard to get working on some mobo's apparently) https://www.amazon.com/ASUS-M-2-X16-V2-Threadripper/dp/B07NQBQB6Z/ https://www.amazon.com/ASUS-M-2-X16-V2-Threadripper/dp/B07NQ... In either case you're looking at max throughput of 11 gigabytes per second, which is roughly 20 times faster than SATA 3's 6 gigabits per second.
- mxfh 7y ago
  As stated, support for that one is not guaranteed, you need to first figure, out if your motherboard configuration supports lane bifucartion, otherwise it won't work, or only one of the installed keys. Cards with PLX switches are are way to fix this if you cant upgrade your whole hardware, but the price point is a multiple of simple bifurcation cards, since you have to integrate a whole PCI switch on-card. The architecture diagrams here are quite helpful: https://www.qnap.com/en-us/product/qm2-m.2ssd https://www.qnap.com/en-us/product/qm2-m.2ssd
- wtallis 7y ago
  Almost all NVMe RAID products—including both that you've linked to—are software RAID schemes. So if you're on Linux and already have access to competent software RAID, you should only concern yourself with what's necessary to get the drives connected to your system. In the case of two drives, most recent desktop motherboards already have the slots you need, and multi-drive riser cards are unnecessary.
  - SlowRobotAhead 7y ago
    PERC HP740 controllers in Dell servers iirc are hardware raid for the flex port U.2 and backplane pcie nvme drives.
    - wtallis 7y ago
      Yes, that's one of the cards that use Broadcom/Avago/LSI "tri-mode" HBA chips (SAS3508 in this case). It comes with the somewhat awkward caveat of making your NVMe devices look to the host like they're SCSI drives, and constraining you to 8 lanes of PCIe uplink for however many drives you have behind the controller. Marvell has a more interesting NVMe RAID chip that is fairly transparent to the host, in that it makes your RAID 0/1/10 of NVMe SSDs appear to be a single NVMe SSD. One of the most popular use cases for that chip seems to be transparently mirroring server boot drives.
      - SlowRobotAhead 7y ago
        So stay under 8 physical NVME and it should be fine?
        wtallis 7y ago
        A typical NVMe SSD has a four-lane PCIe link, or 2+2 for some enterprise drives operating in dual-port mode. So it usually only takes 2 or 3 drives to saturate an 8-lane bottleneck. Putting 8 NVMe SSDs behind a PCIe x8 controller would be a severe bottleneck for sequential transfers and usually also for random reads.
rasz 7y ago
Intel SSDs are known for advertising graceful degradation to Read Only mode, when in reality simply suddenly die during endurance tests.
- wtallis 7y ago
  As I recall, there are at least three problems here: 1. Basically no software is prepared to be "graceful" about their storage suddenly going read-only, especially when the OS is trying to run off that drive. 2. Intel drives at end of life go read-only until the next power cycle, whereupon they turn into bricks. 3. The threshold at which Intel drives go read-only is when the warrantied write endurance runs out, not when the actual error rate becomes problematic. This makes sense if the drive is trying to ensure the flash is still in good enough condition to have long data retention, so that you can reliably and easily recover data from the drive. But (2) already rules that out.
  - StavrosK 7y ago
    > Intel drives at end of life go read-only until the next power cycle, whereupon they turn into bricks. That's inconvenient, given that the first instinct of many people at the first sign of read trouble is to power-cycle the drive. Maybe not in enterprise scenarios, but certainly in consumer ones.

bb88 7y ago

The big problem with one data center drive is that if that goes bad, you still lose all your data. You're assuming their marketing MTBF is correct. They do make NVME raid solutions now -- with the advantage being that NVME can be faster than SATA. And there are various price points for the NVME drives depending upon speed. This one from 2018 (not sure if it has full raid or uses VROC)(EDIT: it requires software raid) https://www.pcworld.com/article/3297970/highpoint-7101a-pcie-nvme-raid-card-review.html https://www.pcworld.com/article/3297970/highpoint-7101a-pcie... This one is cheaper but relies upon Intel VROC (which has been hard to get working on some mobo's apparently) https://www.amazon.com/ASUS-M-2-X16-V2-Threadripper/dp/B07NQBQB6Z/ https://www.amazon.com/ASUS-M-2-X16-V2-Threadripper/dp/B07NQ... In either case you're looking at max throughput of 11 gigabytes per second, which is roughly 20 times faster than SATA 3's 6 gigabits per second.

mxfh 7y ago
As stated, support for that one is not guaranteed, you need to first figure, out if your motherboard configuration supports lane bifucartion, otherwise it won't work, or only one of the installed keys. Cards with PLX switches are are way to fix this if you cant upgrade your whole hardware, but the price point is a multiple of simple bifurcation cards, since you have to integrate a whole PCI switch on-card. The architecture diagrams here are quite helpful: https://www.qnap.com/en-us/product/qm2-m.2ssd https://www.qnap.com/en-us/product/qm2-m.2ssd
wtallis 7y ago
Almost all NVMe RAID products—including both that you've linked to—are software RAID schemes. So if you're on Linux and already have access to competent software RAID, you should only concern yourself with what's necessary to get the drives connected to your system. In the case of two drives, most recent desktop motherboards already have the slots you need, and multi-drive riser cards are unnecessary.
- SlowRobotAhead 7y ago
  PERC HP740 controllers in Dell servers iirc are hardware raid for the flex port U.2 and backplane pcie nvme drives.
  - wtallis 7y ago
    Yes, that's one of the cards that use Broadcom/Avago/LSI "tri-mode" HBA chips (SAS3508 in this case). It comes with the somewhat awkward caveat of making your NVMe devices look to the host like they're SCSI drives, and constraining you to 8 lanes of PCIe uplink for however many drives you have behind the controller. Marvell has a more interesting NVMe RAID chip that is fairly transparent to the host, in that it makes your RAID 0/1/10 of NVMe SSDs appear to be a single NVMe SSD. One of the most popular use cases for that chip seems to be transparently mirroring server boot drives.
    - SlowRobotAhead 7y ago
      So stay under 8 physical NVME and it should be fine?
      - wtallis 7y ago
        A typical NVMe SSD has a four-lane PCIe link, or 2+2 for some enterprise drives operating in dual-port mode. So it usually only takes 2 or 3 drives to saturate an 8-lane bottleneck. Putting 8 NVMe SSDs behind a PCIe x8 controller would be a severe bottleneck for sequential transfers and usually also for random reads.

rasz 7y ago

Intel SSDs are known for advertising graceful degradation to Read Only mode, when in reality simply suddenly die during endurance tests.

wtallis 7y ago
As I recall, there are at least three problems here: 1. Basically no software is prepared to be "graceful" about their storage suddenly going read-only, especially when the OS is trying to run off that drive. 2. Intel drives at end of life go read-only until the next power cycle, whereupon they turn into bricks. 3. The threshold at which Intel drives go read-only is when the warrantied write endurance runs out, not when the actual error rate becomes problematic. This makes sense if the drive is trying to ensure the flash is still in good enough condition to have long data retention, so that you can reliably and easily recover data from the drive. But (2) already rules that out.
- StavrosK 7y ago
  > Intel drives at end of life go read-only until the next power cycle, whereupon they turn into bricks. That's inconvenient, given that the first instinct of many people at the first sign of read trouble is to power-cycle the drive. Maybe not in enterprise scenarios, but certainly in consumer ones.