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Which OS Performs Best With SSDs?
Lucas123 writes "Linux, Vista and Mac OS perform differently with solid state disks. While all of them work well with SSDs, as they write data more efficiently or run fewer applications in the background than XP, surprisingly Windows 2000 appears to be the winner when it comes to performance. However, no OS has yet been optimized to work with SSDs. This lost opportunity is one Microsoft plans to address with Windows 7; Apple, too, is likely to upgrade its platform soon for better SSD performance."
Have they tuned Linux for SSD? Like setting no-op IO scheduler (which gives about 20% speedup on some workloads)?
I suspect that Win2000 and Win98 win because they have the most simple (and stupid) IO schedulers. That's a problem for conventional HDDs, but it's an advantage for SSDs.
Also, they are talking about "Win98 doesn't support wear-levelling technology". But that's incredibly stupid since modern 'disk-like' SSDs do wear-leveling in hardware.
Since they didn't test Solaris, the test is meaningless. It's the only OS in existence right now with caching and data management features designed specifically to take advantage of flash to improve real-world performance. The submitter's assertion to the contrary is a deliberate lie, an assumption that until Microsoft does something it hasn't been done, or at best sheer ignorance.
Read up on the ZFS L2ARC and the use of supercap/DRAM/flash subsystems for separate intent logs that make up the hybrid storage pool. There are plenty of white papers and other material out there, and of course you can also read the source code.
XP will not. OS X will. In fact, OS X will defrag your thumb drive without your permission. It was bad enough that it was wearing my disk for no benefit, but it also made my thumb drive remarkably non-resiliant to power outages.
Your ad here. Ask me how!
>I'm suspicious of the suggestion that a log-based
>filesystem will cure all the ills of the limited flash-
>controller based wear leveling.
Yeah. Total bull.
Anybody who thinks the filesystem can do really well has
bought into the crud from most existing vendors about how
you have to use those things differently. If you really
do believe that, you shouldn't touch an SSD with a ten-foot
pole.
If the flash vendor talks about "limits" in the wear
levelling, and how you have to write certain ways, just
start running away. Don't walk. Run away as fast as you
can.
>A question keeps coming up in my mind about what happens
>when you split an SSD into multiple partitions, and what
>*you want to happen*. I use separate partitions for root,
>boot, and var, because I tend to make root and boot
>read-only.
Again, if your SSD vendor says "align to 64kB boundaries"
or anything like that, you really should tell them to go
away, and you should do what Val said - just get a real
disk instead. Let them peddle their crap to people who are
stupider than you, but don't buy their SSD.
So what you want to happen if you split an SSD into multiple
partitions is exactly nothing. It shouldn't matter
one whit. If it does, the SSD is not worth buying. If it is
so sensitive to access patterns that you can't reasonably
write your data where you want to, just say "No, thank you".
Anyway, I have a good SSD now, so I can actually
give some data:
- Most flash-based SSD's currently suck.
I don't have these ones myself, but last week we had the
yearly kernel summit here in Portland, and a flash
company that shall remain nameless (but is one of the
absolute biggest and most recognizable names in flash)
was selling their snake-oil about how you need to write
in certain patterns.
So I called them on it, and called them idiots. Probably
one reason why I didn't get one of the drives they were
handing out, but one of the people who did get a drive
was the Linux block system maintainer. So he ran some
benchmarks.
Those things suck. You will never get any decent
performance of anything but a very specialized filesystem
out of them, unless you use them as essentially read-only
devices.
For a basic 4kB blocksize random write test, the SSD got
around 10 IOps. That's ten, as in "How many fingers do
you have?" or as in "That's really pathetic". It means
that you cannot actually use it as a disk at all, and
you need some special filesystem to make it worthwhile,
and certainly means that wear levelling is probably not
working right.
(For the math-challenged, 10 IOps at a 4kB blocksize
means 40kB/s throughput and 100ms+ latencies for those
things. It also means that even if some operations are
fast, you can never trust the drive)
- In contrast, the Intel SSD's are performing exactly as
advertised.
I did get one of these, with warnings about how
if I want to get low-power operation etc I need to make
sure that disk-initiated power management is enabled etc.
Whatever. The important thing is that the Intel SSD does
not care one whit where you write stuff, or how you do
it. With the same 4kB random write b
He said, "You'll be able to tell your grandchildren that you helped assemble the first NT supercomputer," and I cringed.