From: Scott Marlowe <scott.marlowe@gmail.com>
To: Mike Smith <mike.smith@enterprisedb.com>
Cc: Christian Nicolaisen <blackbrrd@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: 8x2.5" or 6x3.5" disks
Date: Tue, 29 Jan 2008 09:00:22 -0600
Message-ID: <dcc563d10801290700l5138d13fvb9fa05b66ddc32f2@mail.gmail.com> (raw)
In-Reply-To: <51494DB187D98F4C88DBEBF1F5F6D42303EC56C9@edb06.mail01.enterprisedb.com>
References: <285fb20801281125k641902feo8d74b1c68640d94b@mail.gmail.com>
<51494DB187D98F4C88DBEBF1F5F6D42303EC56C9@edb06.mail01.enterprisedb.com>
On Jan 29, 2008 5:43 AM, Mike Smith <mike.smith@enterprisedb.com> wrote:
>
> You don't mention the capacity of the disks you are looking at. Here is
> something you might want to consider.
>
> I've seen a few performance posts on using different hardware technologies
> to gain improvements. Most of those comments are on raid, interface and
> rotation speed. One area that doesn't seem to have been mentioned is to
> run your disks empty.
>
> One of the key roadblocks in disk performance is the time for the disk heads
> to seek, settle and find the start of the data. Another is the time to
> transfer from disk to interface. Everyone may instinctively know this but
> its often ignored.
>
> Hard disks are CRV ( constant rotational velocity) = they spin at the same
> speed all the time
>
> Hard disk drives use a technology called ZBR = Zone Bit Recording = a lot
> more data on the outside tracks than the inner ones.
>
> Hard disk fill up from outside track to inside track generally unless
> you've done some weird partitioning.
This really depends on your file system. While NTFS does this, ext2/3
certainly does not. Many unix file systems use a more random method
to distribute their writes.
The rest of what you describe is called "short stroking" in most
circles. It's certainly worth looking into no matter what size drives
you're using.
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To: pgsql-performance@postgresql.org
Cc: scott.marlowe@gmail.com, mike.smith@enterprisedb.com, blackbrrd@gmail.com
Subject: Re: 8x2.5" or 6x3.5" disks
In-Reply-To: <dcc563d10801290700l5138d13fvb9fa05b66ddc32f2@mail.gmail.com>
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