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All HDDs that I know have at least 8MB or more of buffer cache (I know that it is for increasing read and write performance on Disk Drivers).

However, I'm just curious: Do SSDs have any buffer/cache system, something similar as HDDs? Do SSDs have even better performance beyond those of HDD buffers?

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@slhck I had already fixed those typos! @Diogo Why did you rollback my edits? –  sblair Jul 12 '11 at 19:49
    
Diogo, please note that when editing your own or other questions, don't rollback edits of others like this one from @sblair. @sblair clearly helped to improve the readability of your question, which you reverted. If you have anything to add, add it to the improved question. –  slhck Jul 12 '11 at 19:50
    
@sblair Sorry, didn't see yours at first because I didn't expect such a huge improvement to get reverted! –  slhck Jul 12 '11 at 19:51
    
Sorry, i was just thinking that it should be write with "Does" instead of "Do". Sorry for my english. –  Diogo Jul 12 '11 at 19:52
    
No worries, no need to apologize! Just trust someone who's from the UK to edit your content :) –  slhck Jul 12 '11 at 19:56

3 Answers 3

up vote 4 down vote accepted

To quote Wikipedia:

A flash-based SSD typically uses a small amount of DRAM as a cache, similar to the cache in Hard disk drives. A directory of block placement and wear leveling data is also kept in the cache while the drive is operating. Data is not permanently stored in the cache. One SSD controller manufacturer, SandForce, does not use an external DRAM cache on their designs, but still achieve very high performance. Eliminating the external DRAM enables a smaller footprint for the other flash memory components in order to build even smaller SSDs.

Of course, the reason they can use less is that they are using memory in the first place to do the storage, so it is already reasonably fast compared to a traditional hard drive, whereas the harddrive needs that cache memory more to make it perform better.

If is also doubtful that they use enough to even warrant listing it as a feature, and it would probably look bad in comarision to traditional drive specs, so they opt to leave it out.

http://en.wikipedia.org/wiki/Solid_State_Drive#Cache_or_buffer

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Nice, thank you again KCotreau. –  Diogo Jul 12 '11 at 13:42

Yes, most SSD's have a cache in volatile memory like SRAM or SDRAM, but it is not necessarily required for high performance. Certainly the size of the cache is less of an indicator of performance with SSDs than it is with hard drives.

You might find this Anandtech article interesting as it discusses how traditional SSD architecture, with SDRAM or SRAM cache compares with the latest SanDisk architecture, which use a mixture of MLC and SLC NAND flash to remove the need for volatile memory completely.

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From reading this concerning the Intel SSD 320 (provides a picture of the board) it seems the onboard RAM is just for controller use. It doesn't seem to utilize any memory for buffering use in the sense that a platter HDD does.

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