Note: My original question was about the reliability of solid state drives in general, so I unwisely posted it to plug-talk. The thread is becoming Linux specific so I am moving this to the general list.
On Sun, Jan 06, 2013 at 07:45:50PM -0800, Larry Brigman wrote: > We have evaluated SSD for quite a while and are just now > gearing up to deploy them. The reliability is good but what > you need to watch is performance. The drive can function but > the performance can fall off without triggering any smart trips. Thanks Larry! I assume you are talking about the block erase problem described here: http://www.anandtech.com/show/2738/8 Which I interpret as "reading is very fast, writing on erased flash blocks is fast, erasing a portion of a block is slow because you have to move pages of data around to do it". This is a "feature" of the physical architecture of NAND flash, where the bits can be very small but the block erase mechanism is large, so they pile a whole bunch of bits into a block to reduce cost, power, and initial read/write time. Unlike a hard disk, writing "1s" into an SSD is very fast, but writing "0s" is done in large bunches, and is slow. This also wears out the flash memory, though new rapid pulse heating techniques are claimed to fix this ( I suspect they will also break wires on the chip ). The following discusses the best linux filesystem with SSD: http://superuser.com/questions/228657/which-linux-filesystem-works-best-with-ssd This thread suggests using ext4 with TRIM. That shows up in the 2.6.33 kernel (I'm using an RHEL6 kernel with 2.6.32, sigh). It also suggests no swap on the SSD, and turning off some of the access flags on the filesystem. This is an 8x5 office. We could schedule a "defragmentation" process in the wee hours after backups, without degrading performance. Are there tools for that? Also, it would be nice if there was a module that could be added to the kernel for evaluating current disk usage with our particular set of tasks, estimating compatibility with SSD. Suggestions? BTW, I have been running two ALIX single board computers as firewalls for years, with compact flash card "disks". They work fine, though they send syslog information to other machines and don't write much to their own disk - about 40 files per day. Keith -- Keith Lofstrom kei...@keithl.com Voice (503)-520-1993 _______________________________________________ PLUG mailing list PLUG@lists.pdxlinux.org http://lists.pdxlinux.org/mailman/listinfo/plug
