What does "4KB Transfer - 2GB Sequential Read" means in SSD benchmark ?

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anderson9987

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I was reading this comparison http://www.anandtech.com/bench/product/1141?vs=665
and i found this "4KB Transfer - 2GB Sequential Read "

But I though that sequential read was used just to measure large files.
I really dont understand what does"4kb transfer- 2gb sequential read " mean.

And why Intel 730 is so much worse than Samsung 840 pro when you compare
"4KB Transfer - 2GB Sequential Read - QD4" ?


thx in advance

anderson
 
Solution
Solandri
Based on the benchmarks listed (0.5k, 1k, 2k, 4k etc up to 8192k), that's probably the ATTO benchmark.
https://www.attotech.com/disk-benchmark/

And "4kB transfer - 2GB sequential" just means they ran ATTO with the total length set to 2GB. That is, ATTO did 2GB worth of 4kB reads to measure that speed.

QD4 means a queue depth of 4. That is, 4 simultaneous reads (or writes) were requested from the drive. On big sequential transfers, this doesn't really matter. On smaller transfers (like 4k), the overhead of requesting and returning the transfer is slower than the SSD and do the read/write, so a higher QD boosts speed. It looks like the Intel SSD has problems processing these parallel requests for really small file sizes quickly...
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Solandri

Solandri

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Based on the benchmarks listed (0.5k, 1k, 2k, 4k etc up to 8192k), that's probably the ATTO benchmark.
https://www.attotech.com/disk-benchmark/

And "4kB transfer - 2GB sequential" just means they ran ATTO with the total length set to 2GB. That is, ATTO did 2GB worth of 4kB reads to measure that speed.

QD4 means a queue depth of 4. That is, 4 simultaneous reads (or writes) were requested from the drive. On big sequential transfers, this doesn't really matter. On smaller transfers (like 4k), the overhead of requesting and returning the transfer is slower than the SSD and do the read/write, so a higher QD boosts speed. It looks like the Intel SSD has problems processing these parallel requests for really small file sizes quickly. The original Anandtech reviewer speculates this is because the 730 is designed as an enterprise SSD, and thus isn't optimized for these really small file sizes.
http://www.anandtech.com/show/7803/intel-ssd-730-480gb-review/5
 
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anderson9987

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Could you tell me me the type of computer activity that would be affected by this low performance?
Besides transfering files from one folder to another .

Could software development be affected anyhow? ( Visual Studio / c#).


 
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Solandri

Solandri

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Yes, compiling code would be disproportionately heavily impacted by slow 4k read/write speeds. When you compile, the computer has to read a bunch of small text files, and writes a bunch of small object files. Then it reads those object files again to link them into a big executable. So lots of small file read/writes.

Booting the computer is also largely affected by 4k speeds. If you ever browse the Windows directory, you'll see lots and lots of small files. It's why even a 8GB cache SSD can drastically speed up boot times. Those small files end up stored in the cache instead of read off the slow HDD.

Games with lots of small data and level files will also be affected.
 
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