Dieter wrote:
JRT> I was considering buying a small 1-2 GByte flash disk form my
system so JRT> I was looking over what was available and didn't find
what I wanted.
JRT> This should considerably speed up a typical desktop Linux system
if used JRT> for swap. JRT> JRT> Perhaps SD cards are a better idea.
I thought these devices had a limited number of writes, and thus were
a bad choice for things like swap?
They claim to have solved that issue. There are plans to use flash
memory for the buffer on a hard disk -- the hybrid disk drive. IAC,
does the operating system still accumulate a list of bad blocks? If so,
the practical limit of life would be when 10% of the blocks were marked
as bad. This would be much longer than the rated life.
Do you have main memory maxed out?
For now yes. I plan to upgrade this year and will probably get a board
that will hold 4 GBytes and probably start with 2 if I can afford it.
Since Linux always uses all of main memory, system performance can
always be improved by adding swap.
For swap you don't need non-volatile memory. There are PCI cards
that accept memory and pretend to be a very fast disk.
Perhaps for the specific purpose of providing swap to a system. regular
memory would be better. But, can you still obtain slower memory
suitable for such a purpose at a comparable price? The flash cards
appear to be less expensive than SDRAM in DIMMs and you don't need a
controller with flash cards.
IAC, just because I would use such a device for swap if it was faster
than my disk but slower than memory doesn't mean that others wouldn't
find some other use for it. The other most common purpose would be to
boot a disk less system.
JRT> So far I could only find them with DMA 0 which seems to be
limited by JRT> the card speed. DMA 0 is 16 MB/sec. The fastest CF
(133x) is 20 MB/s. JRT> SDs come slightly faster at 22.5 MB/sec which
is still slower than DMA 1.
A 7200 rpm SATA drive does 40 MB/s sustained at the slow end of the
platters, and 65-70MB/s sustained at the fast end.
I was looking for something faster than IDE. SCSI 320 approaches 100
MB/s sustained but an 18 GByte and a controller would be rather expensive.
Are you trying to avoid moving parts?
I'm not sure exactly what the design issues are with a disk less system.
Disks are getting rather small if space is an issue.
Product idea: How about a PCIe card with 8 SATA ports and a
documented protocol for NCQ?
That would be useful for a server, but for a workstation I think that 4
HDs would be the practical limit for most uses. Actually, you need a
server size tower to take more than 4 3.5 inch hard drives. Also, it
usually costs more for 4 drives at 1/4 the capacity each (for the same
total capacity).
--
JRT
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