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solid state drives, flash memory, and "swapon"

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January 3, 2007 7:02:35 PM

I'm sure I'm confused here, but I keep reading about Windows Vista's ability to use spare USB flash drives to improve performanace, and now solid state discs made from flash memory (http://www.tgdaily.com/2007/01/03/samsung_32gb_ssd/ ). I'm sure the people that design these are way smarter than me, so can someone please tell me why this is not the linux equivalent of swapon [device of usb stick] And isn't flash memory only good for so many writes? In other words, won't flash memory fail much sooner than a hard drive? Or in still other words, why aren't all linux users regularly typing swapon /dev/sdc1 (or whatever device your usb stick gets mounted on)?
January 3, 2007 7:38:39 PM

You see a lot of firewall configurations using hybrid configurations. The flash portion processes logs much faster than straight disks, once the process is finished the logs are moves off to disk. It almost acts in the same way pagefile does in ms, but the advantages Vista is trying to exploit with flash and hybrid drives, is to use the memory to commit data for faster load time of the OS and Apps. Much in the likeness of suspend mode on the fly. Linux will follow suite soon, but the logical construction and design of the two do not equate to a similar necessities for the hybrid functions.
January 3, 2007 8:11:22 PM

I see, thanks for the info.

So...what confuses me (I'm easily confused), is that flash memory has a limited amount of erase-write cycles. Won't hybrid drives, solid state drives, and flash memory used with Vista suffer from the same limitation and be trashed in a relatively short time? Or are the amount of writes to flash memory limited so that this isn't a problem?
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January 3, 2007 8:17:12 PM

Quote:
I'm sure I'm confused here, but I keep reading about Windows Vista's ability to use spare USB flash drives to improve performanace, and now solid state discs made from flash memory (http://www.tgdaily.com/2007/01/03/samsung_32gb_ssd/ ). I'm sure the people that design these are way smarter than me, so can someone please tell me why this is not the linux equivalent of swapon [device of usb stick]


The Windows Vista Ready Boost feature is not anything like a swap file. It is more like IO cache memory. Flash actually has a SLOWER transfer speed than a hard drive, but the seek time is almost nothing. So, random access to things like the Windows registry which is accessed randomly with small reads/writes will be faster in flash than from a hard drive, but reading large files sequentially will be slower.

Quote:
And isn't flash memory only good for so many writes? In other words, won't flash memory fail much sooner than a hard drive? Or in still other words, why aren't all linux users regularly typing swapon /dev/sdc1 (or whatever device your usb stick gets mounted on)?


Yes.
Yes.
Because the Linux swap file reads and writes full memory pages, usually 64K, at a time. This type of usage will be SLOWER on flash than on a hard drive.
January 3, 2007 8:38:03 PM

Ah, I see... Thanks!
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