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paultman

partitions and SSD's

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Hey everyone :) Long time reader, first time poster :)

Partitions. So with the typical HD's, I'd partition them seperating my os/programs and data files for two reasons 1) performance, the first partion, on the outter surface of the platter(s) are faster and I want my exe's there. 2) backups, my state info and other files are in the second partition, with my OS and non-state info on the first partition. That makes backups/restores of my OS smaller.

Now we've got these nifty new SSD's. The first point no longer applies since it's random access. But it would be nice to still have the separation of os/progs and data if for at least backups & organization However my question is: Will it be slower then a singly partitioned ssd? I've heard about in-drive raiding, and think I see that with larger drives, of the same family, having faster write/read times for the higher capacity ones. if that's the case, how are they spreading data I wonder? If I partition a 60GB drive, 30/30, will only half of the readers read? With I get 1/2 performance?

How do multiple partitions effect SSD performance?

I greatly appreciate any feedback,

Paul

P.S. I'm not taking about partition alignment, which is related to 4k clusters.

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Partitioned performance identical to non-partitioned on SSD. Organisational benefits for backup/restore/reinstallation of OS partition without wiping user data still apply.

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I agree with Spod's reply above regarding performance, and the benefits of using partitions for separate concerns. On the other hand, SSD drives are typically small, and splitting them up into multiple partitions wastes some space. It's a tradeoff, as always.

I've heard about in-drive raiding, and think I see that with larger drives, of the same family, having faster write/read times for the higher capacity ones.

The SSDs currently worth getting for home use, Intels 2nd generation X25-M MLC and the Indilinx controller drives such as OCZ Vertex, do not use "raid". They read & write to multiple flash lines at once, just like PCs have 2 or 3 RAM channels, but they don't use multiple controllers or anything like that.

"RAID" was for a while used on cheap and nasty SSDs with bad controllers, to make them suck less. Avoid these drives.

There is no clear connection between performance and drive size with SSDs. Many models perform exactly the same in all sizes. But it can also change a little, depending on the flash RAM used and its configuration in the different drive sizes.

P.S. I'm not taking about partition alignment, which is related to 4k clusters.

This is important -- align the partitions using diskpart or a similar tool, so that file system block boundaries are aligned with SSD page boundaries. Otherwise you get additional write amplification, and thus more wear and tear on the SSD flash.

Oh, and BTW, Anandtech has recently put up an article on SSDs that's actually pretty good:

http://www.anandtech.com/storage/showdoc.aspx?i=3631

Edited by 270673

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The multi-channel SSD's spread the data over all channels and chips with no performance penalty.

The TRIM command/utilities will not work with SSD's in a RAID (OS or HBA). Some drives are better than others at grouping writes and finding blocks best to re-write. If you partition less of the drives then you can help the SSD's juggle the re-writes and remapping. If you don't format 10GB then the SSD will typically have 10GB ready for a large writes.

The formated location of data on SSD's are not fixed are re-mapped to other locations for wear levelling. Just because the file is sequential according to the file system doesn't mean it's sequential in the SSD memory.

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I agree with Spod's reply above regarding performance, and the benefits of using partitions for separate concerns. On the other hand, SSD drives are typically small, and splitting them up into multiple partitions wastes some space. It's a tradeoff, as always.
I've heard about in-drive raiding, and think I see that with larger drives, of the same family, having faster write/read times for the higher capacity ones.

The SSDs currently worth getting for home use, Intels 2nd generation X25-M MLC and the Indilinx controller drives such as OCZ Vertex, do not use "raid". They read & write to multiple flash lines at once, just like PCs have 2 or 3 RAM channels, but they don't use multiple controllers or anything like that.

"RAID" was for a while used on cheap and nasty SSDs with bad controllers, to make them suck less. Avoid these drives.

There is no clear connection between performance and drive size with SSDs. Many models perform exactly the same in all sizes. But it can also change a little, depending on the flash RAM used and its configuration in the different drive sizes.

P.S. I'm not taking about partition alignment, which is related to 4k clusters.

This is important -- align the partitions using diskpart or a similar tool, so that file system block boundaries are aligned with SSD page boundaries. Otherwise you get additional write amplification, and thus more wear and tear on the SSD flash.

Oh, and BTW, Anandtech has recently put up an article on SSDs that's actually pretty good:

http://www.anandtech.com/storage/showdoc.aspx?i=3631

Thanks, I really appreciate all this feedback!

I'm using a mac, not sure if I can do the file system alignment same was as windows, but i'll look into it.

Before I read anandtech's latest comparison, I ordered an OCZ summit 60GB drive. I was attracted to it's low price, $150 after 30 rebate and it's 128MB cache. However after reading anandtech's article about the samsung controller having 4k write issues, i'm not quite as happy :) but it's undoubtidly a huge upgrade over my rotational drive, and I will probably do a 24gig system and 36gig data partition scheme. This will be on a new snow leopard MBP.

I'll post my progress/findings to my blog at unwiredthinking.com

Again, thanks!

Paul

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