Author Topic: Benchmarking on Mac mini 2018 - slow disk speeds - or how PI uses the disks?  (Read 336 times)

Offline mcgillca

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Hi - I've been wondering about buying a Mac mini 2018 for Pixinsight use. However, looking at the benchmarks, I'm a bit surprised by the swap speed.

Users have reported Blackmagic reports disk read and write speeds for the 1TB disk at around 2.5GB/s (its a bit slower for write speeds for smaller disks), but the PI benchmarking data reports only 764 MB/s.

I was a little surprised since my wife's iMac with a 51GB SSD PI benchmark reports speeds of around 2.4GB/s, which is in line with the Blackmagic speed test.

I then experimented with a RAM disk on my wife's computer - Blackmagic reported about 5GB/s, whilst the PI benchmarking reported only about 1.5GB/s.

There is clearly something more complicated going on here since I would have expected better results with the RAM disk.

In each case, I used 4 temp file instances, so this shouldn't have changed.

Any thoughts?

Colin
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Offline STAstro

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Colin

How do you have your swap space configured for PixInsight?

I have 8 Swap folders configured on my Fusion I/O card, if you add say another three swap folders into PixInsight and perform the benchmark again, you might be where you expect to be

I will be tring this out on my MacBook Pro too very soon

Simon

Offline mcgillca

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Dear Simon,

Hi - thanks for the reply. I did try this on my wife's Mac (I don't know how the reported benchmarks were configured). My default is to have four swap folder on the internal SSD - I've tried 4 to 8, and they all give much the same result.

I then went down to 1 folder, and the speed dropped from ~ 2.4 GB/S to 1.4GB/s, significantly slower but nearly twice speed of the reported Mac mini PI benchmarks.

I'm still puzzled by the RAM disk though - again, I had four swap locations enabled on the ram disk, and the speed was 1.5 GB/s, despite being a factor of two faster in Blackmagic.

Colin
Paramount MX
Ikharos 8" Carbon Truss RC
Atik 460ex
Atik EFW2 with Baader LRGB and HA SII OIII
ONAG with Atik 314L+
http://www.astrobin.com/users/mcgillca/