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Highly Available Block Storage

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Re: Highly Available Block Storage

#92
post #82

Spun one up and ran some quick numbers on a 100GB volume: root@ubuntu-1gb-nyc1-01:~# time dd if=/dev/disk/by-id/scsi-0DO_Volume_volume-nyc1-01 of=test.dat bs=1024 count=10000000 10000000+0 records in 10000000+0 records out 10240000000 bytes (10 GB) copied, 58.0655 s, 176 MB/s real 0m58.248s user 0m2.608s sys 0m41.604s Some quick observations: * Easy to add one when creating a droplet; by default they let you create v…

Don't use dd for those tests it's really bad, especially on VMs.

What should be used for I/O throughput tests instead?

Re: Highly Available Block Storage

#93
post #69

Earlier quoted context omitted.

> in our case, live migration would just be crazy with local spinning disks, we tried it didn't work It looks like Exoscale does live migrations with locally attached SSDs.

Then they'll run into the same problem anyone does doing that: migrating reasonably-sized block devices across a reasonable network takes an unreasonable length of time. Been there, done that, don't want to sit staring at consoles waiting for live disc migrations ever again.

My guess is that they live migrate VMs only before a planned maintenance. Let's say they use a 10 Gbps network, and they use only 1 Gbps of bandwidth for migrating data, then migrating a 200 GB disk would take something like 1 hour, which sounds OK. Can you share some details about your experience?

Re: Highly Available Block Storage

#96
post #65

Earlier quoted context omitted.

You're looking at the wrong market. At Hetzner, you can rent a dedicated server with 2x3TB drives for about $25/month ($0.005/GB, to scale to multiple servers, use Ceph) and a few larger machines for under $100. At OVH you can buy object storage for around 1c/GB and rent a few dedicated servers for less than $100/month, or use their cloud. If you go to the _really_ low end, time4vps will give you a 1TB VPS for 2EUR/m…

Yeah, but I like the DO per hour billing, design, and API. Other than their insecure-by-default SSH key thing, https://digitalocean.uservoice.com/forums/136585-digitalocea... that is.

You can get per hour billing for compute at OVH and I believe they're Openstack based so their API isn't too bad.

Re: Highly Available Block Storage

#97
post #87
post #83

Earlier quoted context omitted.

What do you mean by "really bad", out of interest?

I should rephrase that, it's not "really bad" but the way that most people use it is not good. The main issue is caching from your OS, and caching from the hypervisor ( the one that runs your VM ). There is also the problem about i/o syncing. By default OS buffer the data before writing it to disk.

That's true of all I/O benchmarks, even those which try to do things like call fsync since the lower layers often lie about whether something was committed to durable storage. The only way to do benchmarks reliably is still to make sure that you're reading/writing data which is much larger than the available cache.

In the case of dd, the real reason why it's often a misleading benchmark is that it's the best-case scenario: full-size streaming I/O where each block is only accessed once. Some applications do have that kind of operations pattern but most don't and can see very different performance characteristics because they depend on things like file creation/deletion overhead, random I/O within an open file, read and write contention if the same file is being accessed by multiple processes, etc.

Re: Highly Available Block Storage

#98
post #92
post #82

Earlier quoted context omitted.

Don't use dd for those tests it's really bad, especially on VMs.

What should be used for I/O throughput tests instead?

fio or bonnie++. I've used fio with PerfKitBenchmarker in the past for some cross cloud platform comparisons.

Re: Highly Available Block Storage

#99

Reminder that just a few weeks ago DigitalOcean rolled over on one of their customers and took down 38,000 websites after receiving a claim of infringement from the NRA against a parody site hosted on surge.sh: http://motherboard.vice.com/read/nra-complaint-takes-down-38...

exactly why I moved off of Digital Ocean a couple of years ago, after a similar incident.

Re: Highly Available Block Storage

#100

Reminder that just a few weeks ago DigitalOcean rolled over on one of their customers and took down 38,000 websites after receiving a claim of infringement from the NRA against a parody site hosted on surge.sh: http://motherboard.vice.com/read/nra-complaint-takes-down-38...

DMCA takedown: the new orbital ion cannon
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