Test Disks and DWAA/DWAB

Flame Flame Questions
1

Just ran Test Disks on some new Mac hardware and got some surprising results. BMD and AJA disk tests bench the nvme storage at 5700 MB/s read and write over usb4/tb5.

Uncompressed/Raw
Read: 17233 MB/s (this is faster than TB can go and feels like either a lie or straight from RAM)
Write: 6256 MB/s

DWAA
read = 3017 MB/s
write = 708 MB/s

DWAB
read = 1452 MB/s
write = 335 MB/s

Isn’t DWAB supposed to be faster and better in Flame than DWAA? I am surprised at the results. Do we trust Test Disks for this sort of thing or should I be doing Write nodes and a stopwatch?

2

Remember, compressed formats require overhead to decompress. That’s likely what you’re seeing. Everything has a cost.

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3

Oh, for sure. I was more surprised that DWAA was more performant than DWAB.

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4

DWAB has 5-10% better compression because it operates over 256 blocks rather than 32.

That makes DWAB better for storage size, but not necessarily performance.

Size determines copy / archive speed after you have the files. Maybe not so much while making the files.

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5

Excess RAM in a Mac is used as a file system cache, even without using Flame’s caching. I suspect it’s caching the test file when it writes, and giving you a boost on the read.

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