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I have a Dell MD 3820i full of SSDs on a 10 gig network and all of my benchmarks have random writes maxing out at 45 MB/s. Two different Dell teams have looked it over and and both of them say everything is configured correctly. The escalated pro support guy told me that the performance I was seeing was expected. The pro deploy guy thought that maybe my SSDs were bad. All 20 of them, I guess. I hate Dell so much right now.
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Jul 18, 2018 22:39
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Thanks Ants posted:I'm pretty sure the MD3 is in no way designed as an all-flash box. I'm not saying that your speeds are indicative of everything working fine, but I think filling one up with Dell-priced SSDs is a waste of money. They sold us a Compellant - which we didnt need - but didn't tell us that it required 240V. We run 120V for no good reason. They took the Compellant back and gave us an MD with all flash at a sweet price point. The sweet price point is not worth having to deal with them.
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Jul 18, 2018 23:03
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YOLOsubmarine posted:What benchmark tool are you using? How many workers, what is the IO size, what queue depth(s) how many concurrent IOs per host, etc? What latencies are you seeing at max IO rate? Crystal Disk Mark on default settings - 4kb with 8 queue 8 thread and 32 queue 1 thread came up with the weird results. To a lesser extent, 1 queue 1 thread was also interesting. We looked at the performance tab in the Dell MD config tool and it came up with more or less exactly the same figures. I ran the same benchmark against a number of configs, here is what I saw: SSD RAID 6, SSD RAID 10, SSD Disk Pool (Dell's 'something like RAID6' implementation'), and HDD RAID 10 all had the same figures - roughly 40 MB/s for 8q/8t and 32q/1t and 10 MB/s for 1q/1t. SSD RAID 10 locally installed behind some PERC on one of my ESX hosts returned 400 MB/s for 8q/8t and 32q/1t and 80 MB/s for 1q/1t. My laptop with a consumer level SSD returned on the order of 150 MB/s for 8q/8t and 32q/1t and 20? MB/s for 1q/1t. I acknowledge that synthetic benchmarks aren't real world, and I don't know how to properly benchmark storage. We were just looking to compare the new SSD arrays to our existing spinning disks to see whether we needed to do a combination of RAID levels to hit our space targets
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Jul 19, 2018 00:35
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The VM is residing on a datastore. Can you suggest a tool that would give me, a non-expert, more valuable insight?
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Jul 19, 2018 05:20
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We use about 20 TB SSD and 50 TB HDD in our datacenters, block only. I have a Dell ME series unit. It, uh, gets the job done, I suppose. I'm not familiar with any other manufacturers units that offer a 10 GbE iSCSI chassis that will take disks and flash, and there's neither money nor desire to run all flash. We just don't need it.
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Aug 19, 2021 06:36
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