[nmglug] production server question follow-up

[Andres Paglayan]

On Fri, 2009-10-09 at 13:32 -0600, Brendan wrote:

> On 10/09/2009 09:32 AM, Andres Paglayan wrote:
> > now I just ordered the hardware, since the chassis supports 8 disks, and
> > the mobo 6,
> > so I purchased 8 disks just to have two identical spares sitting there
> > unplugged.
> 
> Two port SATA controllers are $20.  Pick one up and get those spares active.

thanks for the good duh moment for me,

> 
> > This means that I'll have 6 disks running on the machine,
> > the server does constant little writes, and probably 50 times more
> > little reads.
> > mostly from the DB
> 
> Since you have more disks I'll renew my suggestion that you use one set 
> for DB and another for other IO modes.
> 
> > Since I don't see myself changing or adding disks during the life of the
> > server,
> > I will not do LVM on top.
> 
> That's too bad.  LVM snapshots are freaking awesome.
> 
> > three mirrored groups of two, and then stripping, raid 10 (3/6
> > available, 2 or 3 can fail)
> 
> Uh, parser error.  Are you saying raid10(raid1,raid1,raid1)?  Or are you 
> saying raid0(raid1,raid1,raid1)?  The former means you can lose between 
> 2 and 4 drives and keep going.  The latter means, in theory, 2 drives 
> dying could lose data.  Remember that you can do RAID1 with more than 2 
> disks.  A 3 disk mirror means you have 3 copies of each drive.  It's a 
> little brute force, but it works.
> 

I meant tree sets of mirrored pairs,  then those three sets stripped,
but now I see that having two in the same set means death,
so a no go,
the three disk mirror option makes 2/6 available so another no go,


> > raid 6 (4/6 available, 2 can fail)
> 
> Yep.


with other two alive, probably raid 6 with two hot spares is not a bad
idea,
or as suggested, having two groups, one dedicated for the db, 
and other for the rest of the file system

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