[Dovecot] Howto add another disk storage

[Adrian M]

On Thu, Jul 5, 2012 at 12:35 PM, Stan Hoeppner <stan at hardwarefreak.com> wrote:
> On 7/5/2012 2:44 AM, Adrian M wrote:
>
>> Hi Stan,
>> I know how to add drives to the storage and how to grow the existing
>> filesystem, but such big filesystems are somehow new to mainstream
>> linux. Yes, I know some university out there already have pentabytes
>> filesystems, but right now stable linux systems have trouble
>> formatting ext4 partition over 16T.
>> All this is telling me that is safer to have two or tree smaller
>> filesystems than a big one. Dovecot has a nice feature for this
>> "Directory hashing" http://wiki.dovecot.org/MailLocation/
>
> At 16TB+ scale with maildir you should be using XFS on kernel 3.x, not
> EXT4.  Your performance will be significantly better, as in 30% or much
> more.  The typical XFS filesystem in the wild today is 50TB+ and there
> are hundreds of XFS filesystems well over 100TB deployed around the world.
>
> NASA has XFS filesystems of 380TB and 535TB, and also has multiple 1PB+
> CXFS (cluster XFS) filesystems.  20TB is a tiny snack for XFS, 500TB is
> lunch, 1PB is a big supper.  A single XFS can scale to 16 Exabytes, or 1
> million terabytes, though the largest deployed so far that I'm aware of
> is NASA's 535TB XFS.  It'll scale to anything you'll ever throw at it,
> and much more.
>
>> What I don't know is a nice way to migrate from a single directory no
>> hashing to more than one and hashing.
>
> It's a good time to migrate to XFS.
>
> --
> Stan

Hi Stan,
I already have xfs, and kernel 3.x. Switching from kernel 2.6.x to 3.x
a couple months ago did indeed decrease the iops number.