scylla iotune minimum_io_size

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Mahdi Kamali

<mahdi57.kamali1@gmail.com>

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Nov 19, 2022, 12:06:09 PM11/19/22

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Hello.

Scylla iotune evaluates my disk with minimum_io_size=256KiB.

I saw in an issue that this value comes from /sys/block/<dev_name>/minimum_io_size.
But this value is too large and decreases read and write IOPS to about 10K (With 3GBps throughout!)
I have a RAID0 Array on 3 SSD disks.

Now I have two questions:
1. Is this good value for I/O size or should I change that?

2. Can I change this value after writing data in scylla?

Pavel Emelyanov

<ovzxemul@gmail.com>

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Nov 27, 2022, 7:01:25 AM11/27/22

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суббота, 19 ноября 2022 г. в 20:06:09 UTC+3, mahdi57...@gmail.com:

Hello.
Scylla iotune evaluates my disk with minimum_io_size=256KiB.

Wow

I saw in an issue that this value comes from /sys/block/<dev_name>/minimum_io_size.
But this value is too large and decreases read and write IOPS to about 10K (With 3GBps throughout!)

Absolutely

I have a RAID0 Array on 3 SSD disks.
Now I have two questions:
1. Is this good value for I/O size or should I change that?

iotune doesn't allow to change that value

2. Can I change this value after writing data in scylla?

It would be too late, since if iotune ran with large minimum_io_size then io_properties.yaml would already contain smaller iops. I wonder how come the minimul io size got to that big value in the /sys file...