| |||||||||||||
SSD write leveling?SSD write leveling?Posted Jul 4, 2008 5:11 UTC (Fri) by Cato (subscriber, #7643)In reply to: SSD write leveling? by wtogami Parent article: Acer's Linpus Linux Lite (Fedora) ultra portable laptop piles the pressure on Microsoft (FSM)
I don't think you can buy an SSD without an FTL (Flash Translation Layer) that does wear levelling. This article from a good site on SSDs talks about how in practice it's very unlikely an SSD will wear out: http://www.storagesearch.com/ssdmyths-endurance.html - given current flash write speeds and usage patterns it's more reliable than a hard disk.
(Log in to post comments)
SSD write leveling? Posted Jul 4, 2008 6:22 UTC (Fri) by wtogami (subscriber, #32325) [Link] I have been well aware of the SSD myths for a while now. Has it been explicitly stated that these ultraportables have write levelling? I wouldn't be surprised if some of the manufacturers don't in order to cut costs. Just being cautious here.
SSD write leveling? Posted Jul 4, 2008 10:02 UTC (Fri) by NRArnot (subscriber, #3033) [Link] Isn't it also the case that a flash block (almost) always fails during write? So if the SSD can't handle it with bad block relocation, the filesystem will mark the block as bad and put one's data elsewhere. Unless it's a really dumb filesystem that hammers on the one block that can't be relocated (like FAT floppy disks did!) It's far worse if a block is successfully written, and then goes bad later, as often happens to hard disks when they start degrading mechanically.
SSD write leveling? Posted Jul 4, 2008 14:19 UTC (Fri) by Cato (subscriber, #7643) [Link] It's worse than just losing a single block. A flash erase block can include many filesystem blocks as it's quite large - anything from 16 to 512 KB according to http://en.wikipedia.org/wiki/Flash_memory#NAND_memories. And in some devices with poor FTLs, interrupting a single write can cause the whole device to fail - it's important that when the device comes back up, the FTL checks for partially written erase blocks and marks them as bad. Unfortunately FTLs appear to be mostly undocumented so you just have to rely on going for mid to high end flash products from a reputable vendor, assuming you care about reliability. Embedded flash products (e.g. CF drives) seem to have good reliability specs and may be a good option, at some extra cost.
SSD write leveling? Posted Jul 4, 2008 17:19 UTC (Fri) by jwb (guest, #15467) [Link] If they didn't have wear leveling, they would wear out within an hour. You probably wouldn't even get the OS installed before they wore out.
SSD write leveling? Posted Jul 4, 2008 13:52 UTC (Fri) by tzafrir (subscriber, #11501) [Link] I don't understand his math. First off, the limitation of number of writes is for a block. Not for a specific byte in a block. Thus the worst load for a flash is not a sequesial logger. It is an application that wries 1 then 0 and then 1 again to the same byte and does this to random bytes all over. He later writes an explanation as to why that data recorder "does the fastest damage". But I fail to folow the reasoning there.
|
|||||||||||||