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Nomad_Soul

480GB Sandforce drives - poor 4k random write performance?

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Hi all,

I was all set to buy an Intel 520 480gb drive when, after doing a little research on the 480gb model specifically, found that it and apparently other sandforce 480gb drives suffer from some performance issues in the area of 4k writes. In terms of the synthetic benchmarks, the differences in performance looked fairly dramatic compared to the 240gb sandforce drives and some non-sandforce controller drives. I'll admit that I'm pretty new to researching SSD benchmarks.

I have a fairly good impression of Intel products and liked their 5 year warranty, so this news has sort of thrown my plans into disarray. How much of a real world performance hit would I be looking at by going with the Intel 520 480gb vs some of the competing SSD options out there in the range of 480 to 512gb? Am I taking the 4k random write tests too seriously? Any thoughts on the matter would be appreciated.

A quote I found elsewhere talks about it further:

I should note that as with other 480GB SandForce-driven SSD's, *any* SandForce 2281 SSD with a capacity greater than 256GB will see a dip in 4K IOPS performance. This is due to the way the SF controller handles the mapping of LBA's. To double capacity from 240GB to 480GB, the SandForce controller's finite number of allocations must be reconfigured to utilize 8KB blocks (up from the standard 4KB - intentionally matched to the NTFS 4KB cluster size). This negatively impacts IOPS performance as a 4KB random write translates to the equivalent of an 8KB random write once the added overhead is taken into account.

This is also clear in the Intel specs, as incompressible 4KB writes see a near 50% cut when comparing the 480GB to the 240GB capacity points.

This review goes into it further still and I've noticed similiar problems with 480gb sandforce models from other brands in other reviews.

Edited by Nomad_Soul

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How much of a real world performance hit would I be looking at by going with the Intel 520 480gb vs some of the competing SSD options out there in the range of 480 to 512gb? Am I taking the 4k random write tests too seriously?
REAL-WORLD?

Unless you exclusively sit on SSD benchmarks all day, or you have some application that is heavily 4K dependent, I doubt you'd notice any difference at all. Period.

I have some very specific customers here who are 4K heavy in their use, but even for them, many of their writes are 8K or 16K or whatever as well. The hit is invisible in reality for 99% of users. The key is, are you the 1% (more like 0.05%) who actually is 4K write heavy and would be impacted. For the average user, though? I doubt it.

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