3 ms·
At Google my colleague developed a simple test that made vibration effects very obvious (this was in 2008). In a server with a bunch of disks, do random reads o
by slewis 10y ago
At Google my colleague developed a simple test that made vibration effects very obvious (this was in 2008). In a server with a bunch of disks, do random reads or writes on all but one disk. On the final disk, do sequential reads. Back then you could get on the order of 100MB/s sequential read speed on the outer edge of a hard drive in ideal conditions. Under this test performance would dive to something like 10MB/s or worse. All of the seeking would cause vibration, which caused misreads on the disk under test. When a bad read happens a hard drive has to wait until the next rotation to try again. We eventually fixed this with better damping.
- deegles 10y agoI think it's been known for a while! Here's an old video of a guy inducing read latency spikes by shouting at some servers: https://www.youtube.com/watch?v=tDacjrSCeq4 https://www.youtube.com/watch?v=tDacjrSCeq4
- Twirrim 10y ago"a guy" in this case being Brendan Gregg, http://www.brendangregg.com/ http://www.brendangregg.com/, one of the prominent experts in server performance!
- sliken 10y agoI had an argument from a user who wanted consumer drives instead of "RAID edition drivers". So I ran a test in a 1U server with 8 or so 15k rpm fans. With consumer drive outside the case, on a bench: http://broadley.org/bill/consumer-no-vibration.png http://broadley.org/bill/consumer-no-vibration.png Inside: http://broadley.org/bill/consumer.png http://broadley.org/bill/consumer.png Server drive inside: http://broadley.org/bill/server.png http://broadley.org/bill/server.png We went with the RAID edition.
- deleted 10y ago[deleted]
- raubitsj 10y agoI am that colleague. While it great that Backblaze releases this information, there are many factors that you need to keep in mind when looking at this data. With respect to vibration: we found vibration caused by adjacent drives in some of our earlier drive chassis could cause off-track writes. This will cause future reads to the data to return uncorrectable read errors. Based on Backblaze's methodology they will likely call out these drives as failed based on SMART or RAID/ReedSolomon sync errors.
- swampthinker 10y agoHN is amazing.
- Jgrubb 10y agoThreads like this are what it's all about :)
- locusm 10y agoDoes Google use off the shelf drives like these guys?
- slewis 10y agoI don't think I can comment on that! Sorry. Someone who is working on storage at Google today would have a better idea of what's public vs not.