8 ms·

Just wondering how it is compare to HDD: (Here's my calculation base on some assumptions, feel free to correct it if you see any errors.) 2.5PB = 2500TB = 2,

Just wondering how it is compare to HDD: (Here's my calculation base on some assumptions, feel free to correct it if you see any errors.) 2.5PB = 2500TB = 2,500,000 GB 2,500,000 GB / (80MB /s typical HDD Speed ) = 31,250,000 seconds = 8680 Hours = 361 days. It will take HDD 361 days to write 2.5PB at 80MB/s. I wonder how many HDD can survive 361 days of 80MB/s non stop?

RandomBK 10y ago
> I wonder how many HDD can survive 361 days of 80MB/s non stop? I wonder how many consumer HDDs can survive that load. I would be shocked if datacenter-grade drives fail after only 361 days of continuous load.
- userbinator 10y ago
  80MB/s sequential reads or writes is probably something consumer HDDs can survive for several years. The platters are always spinning, the only difference is that now the drive is continuously reading or writing what's under the head. It's the random accesses (and associated seeks) which stresses them. There are various comparisons out there which conclude "datacenter-grade" is largely a marketing/warranty thing; the drives themselves may be nearly identical in design.
cuchulain 10y ago
Drive vendors are now publishing per-year write workloads for drives. EG, datacentre-grade SATA and near-line SAS drives like the WD RE (https://www.wdc.com/en-um/products/business-internal-storage/wd-re.html https://www.wdc.com/en-um/products/business-internal-storage...) and Seagate Enterprise Capacity (http://www.seagate.com/au/en/enterprise-storage/hard-disk-drives/enterprise-capacity-3-5-hdd/ http://www.seagate.com/au/en/enterprise-storage/hard-disk-dr...) are rated for 550TB/year. Lower-end drives (NAS, cold-storage, desktop models) are rated less. Seagate's overall Enterprise/Datacentre lineup (http://www.seagate.com/au/en/enterprise-storage/hard-disk-drives/ http://www.seagate.com/au/en/enterprise-storage/hard-disk-dr...) ranges from 180TB/year to 550TB/year, and elsewhere on Seagate's site they indicate that a 550TB/year is "10x more than desktop drives". These are all just ratings though. The theory is that over a population of drives, you'll see a higher failure rate than predicted if you do higher than the rated workload per year. WDC used to have a whitepaper on it called "Why Specify Workload", but it's no longer on their site. I have in some cases seen enterprise sata drives pushed to the kinds of workload you're talking about - 2.5PB in a year - and seen in the order of 10% fail over that time, with a drive that normally has a ~0.5% AFR.
verytrivial 10y ago
Then again, I wonder how much impact write amplification[1] can have on hitting that limit without actually pumping that many bits towards the drive. [1] https://en.wikipedia.org/wiki/Write_amplification https://en.wikipedia.org/wiki/Write_amplification
taspeotis 10y ago
80 MB/s would imply sequential IO. Much harder test if it were random IO - the drive head would move all over the place all day long.

RandomBK 10y ago

> I wonder how many HDD can survive 361 days of 80MB/s non stop? I wonder how many consumer HDDs can survive that load. I would be shocked if datacenter-grade drives fail after only 361 days of continuous load.

userbinator 10y ago
80MB/s sequential reads or writes is probably something consumer HDDs can survive for several years. The platters are always spinning, the only difference is that now the drive is continuously reading or writing what's under the head. It's the random accesses (and associated seeks) which stresses them. There are various comparisons out there which conclude "datacenter-grade" is largely a marketing/warranty thing; the drives themselves may be nearly identical in design.

cuchulain 10y ago

Drive vendors are now publishing per-year write workloads for drives. EG, datacentre-grade SATA and near-line SAS drives like the WD RE (https://www.wdc.com/en-um/products/business-internal-storage/wd-re.html https://www.wdc.com/en-um/products/business-internal-storage...) and Seagate Enterprise Capacity (http://www.seagate.com/au/en/enterprise-storage/hard-disk-drives/enterprise-capacity-3-5-hdd/ http://www.seagate.com/au/en/enterprise-storage/hard-disk-dr...) are rated for 550TB/year. Lower-end drives (NAS, cold-storage, desktop models) are rated less. Seagate's overall Enterprise/Datacentre lineup (http://www.seagate.com/au/en/enterprise-storage/hard-disk-drives/ http://www.seagate.com/au/en/enterprise-storage/hard-disk-dr...) ranges from 180TB/year to 550TB/year, and elsewhere on Seagate's site they indicate that a 550TB/year is "10x more than desktop drives". These are all just ratings though. The theory is that over a population of drives, you'll see a higher failure rate than predicted if you do higher than the rated workload per year. WDC used to have a whitepaper on it called "Why Specify Workload", but it's no longer on their site. I have in some cases seen enterprise sata drives pushed to the kinds of workload you're talking about - 2.5PB in a year - and seen in the order of 10% fail over that time, with a drive that normally has a ~0.5% AFR.

verytrivial 10y ago

Then again, I wonder how much impact write amplification[1] can have on hitting that limit without actually pumping that many bits towards the drive. [1] https://en.wikipedia.org/wiki/Write_amplification https://en.wikipedia.org/wiki/Write_amplification

taspeotis 10y ago

80 MB/s would imply sequential IO. Much harder test if it were random IO - the drive head would move all over the place all day long.