Mailinglist Archive: opensuse (933 mails)

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Re: [opensuse] openSUSE on SSD?
  • From: Anton Aylward <anton.aylward@xxxxxxxxxx>
  • Date: Tue, 01 Jun 2010 08:37:27 -0400
  • Message-id: <4C04FF07.40309@xxxxxxxxxx>
Adam Tauno Williams said the following on 06/01/2010 07:53 AM:
On Tue, 2010-06-01 at 13:25 +0200, C wrote:
There is that, but... on computers I've seen running on SSD drives,
the boot cycle, and application startup is a LOT faster.

Really? I've seen demonstrations of that and not been impressed. You
could get, IMNSHO, a bigger performance boost by spending that same
amount of money on a lot more RAM. I've got spinning disks and 6GB of
RAM and apps start pretty close to instantly. An order-of-magnitude
difference I doubt would even be noticeable.

*sigh*

One the whole I agree with Adam, but there are exceptions.

Back in 1984 at a local meeting of the UNIX Users Group someone was
preaching the virtues of a new disk board that had a huge RAM cache.
It gave that 'orders of magnitude' performance increase to the then
extant versions of UNIX, most notably SCO. I spoke out against it.
I was at that time a kernel hacker and specialised in disk drivers.
The SCO OS at that time had just the one (V7) file system. Data writes
were async, structure writes were sync. The 'bottom half' of the driver
didn't know which, so this cache board didn't know which either. As a
result, a crash that could be recovered with FSCK one a normal system
could not be recovered with the cache board.

I pointed out that spending the money on the same amount of RAM for the
system would be more productive for a number of reasons, including less
swapping. UNIX did good cache management and buffering. It has only
got better.

The cache board enthusiast was not there the next month, nor the one
after that. When he did turn up he admitted he'd been away because he'd
been rebuilding his file systems after a crash.

OK, so this doesn't apply to SSD. And SSD is a moving target. But some
points do hold. Adding more RAM will always help simply because it
reduces the amount of disk activity - even if you are not swapping and
paging. There's more buffer for directory and inode when searching file
names to open files. RAM is faster than the fastest SSD, even if the
SSD were faster than the RAM because of the overhead of going though the
drivers & interface :-) Buy RAM when you can. Heck, it cheap enough
these day!

The exception?
Laptops. Only so many slots and a comparatively low top limit on the
amount of RAM. Unlike desktops, laptops (and netbooks and slates and
tablets) are 'closed' devices. There's not a lot you can replace.

Of course devices like this:
http://www.linuxfordevices.com/c/a/News/Seagate-Momentus-XT/?kc=LNXDEVNL052610
are very attractive for laptops, slates and netbooks, especially at $150
for a 500G drive!


--
Knowledge will forever govern ignorance: And a people who mean to be
their own governours, must arm themselves with the power which knowledge
gives.
--James Madison, quoted on the Library of Congress
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