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January 25th, 2022 07:00
MD3220 slow sequential read speed
Hello,
We have MD3220 SAS connected to two HPE host with ESXi 6.7U3
(SAS port have maximum goodput 0.8*4*6Gbps=19.2Gbps=2.4 GB/s)
RAID6 (16*HDD 10k), 128K stripe, 32K cache block, enabled dynamic cache read prefetch.
(each HDD can sequential read 200MB/s, thus RAID6 can maximum 200*(16-2)=2800 MB/s)
VM disk: SCSI controller VMware Paravirtual, Thick Provision Eager Zeroed, NTFS 64KB cluster.
we need to get the maximum performance for sequential reading with 1MB block size and QueueDepth=1.
but disk benchmark show only 733MB/s for sequential read speed:
Why MD3220 so slow?
No Events found!
maa1
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January 25th, 2022 12:00
Yes, HPT enabled (without HPT bench show W/R=309/539).
But 733 MB/s is too low even for systems without HPT!
DellEMCSupport
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January 25th, 2022 12:00
Hi,
Do you have the high performance tier license? https://dell.to/3u7lAYW That document has some other performance information as well. It may also be a limitation of the controller cache or pcie lanes. Let us know if you have any additional questions.
DellEMCSupport
631 Posts
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January 25th, 2022 13:00
Is the performance the same with real world data usage and not artificial load? Are the drives from Dell? Have you tried with fewer drives and different sets of drives? It is possible a drive is not performing well or failing and holding back the whole array. In addition, you may want to try different cables.
maa1
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January 27th, 2022 02:00
>>Is the performance the same with real world data usage and not artificial load?
for example - file copy between logical disks inside VM:
>>Are the drives from Dell?
Yes
>>Have you tried with fewer drives and different sets of drives?
No
>>It is possible a drive is not performing well or failing and holding back the whole array.
drives look good - no errors in the log
>>In addition, you may want to try different cables.
why?
maa1
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January 27th, 2022 08:00
>>Triying with fewer drives and different sets of drives
this storage is in use and I can't delete an existing virtual disk
>>When you have performance issues it's difficult to find out the problem.. You need to discard options until you get to a conclusion.
my guess - a very unoptimized for QD=1 firmware MD3220
DiegoLopez
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2.7K Posts
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January 27th, 2022 08:00
Hello @maa11,
Triying with fewer drives and different sets of drives can show if it is a current configuration problem or the problem might be on a different reason.
Regarding the cables, is the same logic.. When you have performance issues it's difficult to find out the problem.. You need to discard options until you get to a conclusion.
Regards.