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From:Matt W Date:February 21 2004 1:47am
Subject:Re: Improving seek/access times -- does RAID help?
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Hi Ted,

Heh. :-)  This could be many GBs.  There's no problem reading rows that
are in RAM (cached by the OS) -- can read over 10,000/second.  If
there's enough RAM, the OS will take care of it (you could cat table.MYD
to /dev/null). No ramdisk necessary. :-)

BTW, this is for MySQL's full-text search.  It works pretty well (fast)
as far as doing the lookups and searching in the index.  That's not a
concern at all.  The problem is that it *has to* read the data file for
each matching row (and possibly non-matching rows, depending on the
search). :-(  Searches need to be reasonably fast on millions of rows,
while possibly reading 10s of thousands of data rows.  It takes a lot
more time when those rows aren't cached.

The only thing I've thought of so far is symlinking the data file on a
separate drive, but I'm not sure how much that will actually help.


Matt


----- Original Message -----
From: <Ted.A.Gifford@stripped>
Sent: Friday, February 20, 2004 7:24 PM
Subject: RE: Improving seek/access times -- does RAID help?


> Run everything off a ramdisk ;-)
>
> Ted Gifford
>
> -----Original Message-----
> From: Matt W
> Sent: Friday, February 20, 2004 5:21 PM
> Subject: Improving seek/access times -- does RAID help?
>
> Hi all,
>
> Can anyone tell me whether or not some kind of RAID will improve the
> seek/access times during lots of random reads from, say, MyISAM data
files?
> I *do not care* about improved [sequential] transfer rates; I want the
> fastest possible random access.
>
> I'm thinking that RAID won't give an improvement in this case, because
the
> disks can't know where to read from until MySQL issues the seek calls.
:-(
> About the only thing I can think of that may help is if you're using
> striping, there won't be as much data on each disk so the head would
need
> shorter seeks.
>
> If RAID doesn't help the situation, any other ideas if the sub-6ms
access
> times of the fastest 15K SCSI drives isn't fast enough? :-)
>
>
> Thanks,
>
> Matt

Thread
Improving seek/access times -- does RAID help?Matt W21 Feb
  • Re: Improving seek/access times -- does RAID help?Dan Nelson21 Feb
  • Re: Improving seek/access times -- does RAID help?beacker21 Feb
RE: Improving seek/access times -- does RAID help?Ted.A.Gifford21 Feb
  • Re: Improving seek/access times -- does RAID help?Matt W21 Feb
    • Re: Improving seek/access times -- does RAID help?Sasha Pachev23 Feb