Re: [tlug] SSD caching of 10x 10GB files on slow NAS

[Miles Colman <mcolman@example.com>]

Thanks Curt! Your point is well taken. The problem is slow random access to 10 GB files on the NAS. About 10 to 30 10 GB files will be open at any one time. The slowness is annoying for users. I don't want to refactor the code for loading and accessing data sets since it is probably written for speed already and anyway written by other smarter people. I will check more about the hardware that we use and try to give a high level overview afterwards.

On Fri, Dec 28, 2012 at 11:04 AM, Curt Sampson <cjs@example.com> wrote:

On 2012-12-28 10:10 +0900 (Fri), Miles Colman wrote:

> ...to make loading 10 GB files from a slow NAS (where the files

> live) snappy for about 5 users at once. I'm guessing this would be
> simple if the NAS were actually just a 2 TB drive installed in a
> rackmount server with an open drive bay, and adding the SSD just meant
> connecting it.

I don't know if you realize this, but you have restated your problem
from "I'd like these files to load fast for the user" to "I'd like to
move these files into the serer's RAM just a little more quickly, or
have the server do random access operations on these files a lot more
quickly."

If you don't realize you've done this, you want to step back and just
give us a summary of everything between the drive in question and the
user, what application the user is using, and what's painful about the
user's experience, so that we can help you find out where the bottleneck
is.

Applying a good solution to the wrong part of the problem (e.g.,
doubling the speed of a component that is slowing you down by only 1%)
won't make any perceptable difference to the real problem. Unless you've
confirmed that the problem is indeed where you implicitly stated where
it was above, it could well be that your server is fine and you need
make no changes there at all.

cjs
--
Curt Sampson         <cjs@example.com>         +81 90 7737 2974

To iterate is human, to recurse divine.
    - L Peter Deutsch

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