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Why the negativity towards compression on ssd's?

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a b G Storage
November 28, 2012 9:10:08 PM

whenever i read a ssd review of a non sandforce drive i see how they point out that it dosent do any type of compression and how this is a good thing. maybe im missing something but i dont follow that logic. the problem with sandforce gen2 controllers is they are getting old and have to rely on compression to compete with the newer samsung/marvel/lamd/indilinx controllers. when its incompressible data sandforce drives cant compete. but this doesnt mean compression is a bad thing. image an 840 pro that compressed data. what would be bad about that? it would still have the same speed as it currently has for incompressible data and could potentially speed up compressible data transfers. im sure people will say it doesnt matter because theyre bottlenecked by sata3 and nand anyway. compression still minimizes write amplification because it takes up less space and who knows in the future when a new nand standard or pcie/sata express drives come out that extra speed could be useful. i think compression gets a negative association because sandforce drives had all those bsod issues and at this point the controller is old and cant compete with incompressible data. am i wrong?

on a side note what is sandforce doing? they released the gen2 controller in 2010 and they were the dominant controller for a long time. since then they have havent released a new controller and we see most established ssd companies trying to switch to something else thats more competitive.
November 29, 2012 12:14:28 AM

Compression itself isn't bad, but taking a large hit in performance because something isn't compressible doesn't leave a good taste.

When it comes to people who want max performance, they typically side on brute-force and not finesse.
a b G Storage
December 2, 2012 5:30:53 PM

yea after thinking more about it after i posted the 840 example wouldnt be completely accurate. there would be some overhead to check if the data was a duplicate or compressible. im not sure how much overhead there is and if thats why incompressible data is so slow on sandforce drives. it could be thats just how fast the controller is when it cant rely on compression. so if they didnt use compression all data would just be written at the speed incompressible data is currently written at.

the other thing is the compression/deduplication introduces a lot more complexity and that can cause problems like all the bsod issues sandforce had. ive tried searching for info about exactly what sandforce is doing with compression and deduplication but i cant find anything other then the normal generalizations made in reviews and forums. ive also read articles about how trim is still broken on incompressible data.

http://www.anandtech.com/show/2899/3
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