zfs discuss - Jun 2010 - Recomendations for Storage Pool Config

Good morning all.

This question has probably poped up before, but maybe not in this exact way...

I am planning on building a SAN for my home meta centre, and have some of the
raid cards I need for the build. I will be ordering the case soon, and then the
drives. The cards I have are 2 8 port PXI-Express cards (A dell Perc 5 and a
Adaptec card...). The case will have 20 hot swap SAS/SATA drives, and I will be
adding a third RAID controller to allow the full 20 drives.

I have read something about trying to setup redundancy with the RAID
controllers, so having zpools spanning multiple controllers. Given I
won''t be using the on-board RAID features of the cards, I am wondering
how this should be setup...

I was thinking of zpools: 2+2+1 X 4 in ZRAID2. This way, I could lose a
controller and not lose any data from the pools... But is this theory correct?
If I were to use 2Tb drives, each zpool would be 10Tb RAW and 6TB useable...
giving me a total of 40Tb RAW and 24Tb usable...

Is this over kill? Should I be worrying about losing a controller?

Thanks in advance.

--Tiernan
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Good morning all.



This question has probably poped up before, but maybe not in this exact way?



I am planning on building a SAN for my home meta centre, and have some of
the raid cards I need for the build. I will be ordering the case soon, and
then the drives. The cards I have are 2 8 port PXI-Express cards (A dell
Perc 5 and a Adaptec card?). The case will have 20 hot swap SAS/SATA drives,
and I will be adding a third RAID controller to allow the full 20 drives.



I have read something about trying to setup redundancy with the RAID
controllers, so having zpools spanning multiple controllers. Given I won?t
be using the on-board RAID features of the cards, I am wondering how this
should be setup?



I was thinking of zpools: 2+2+1 X 4 in ZRAID2. This way, I could lose a
controller and not lose any data from the pools? But is this theory correct?
If I were to use 2Tb drives, each zpool would be 10Tb RAW and 6TB useable?
giving me a total of 40Tb RAW and 24Tb usable?



Is this over kill? Should I be worrying about losing a controller?



Thanks in advance.



--Tiernan
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Tiernan,

Hardware redundancy is important, but I would be thinking about how you
are going to back up data in the 6-24 TB range, if you actually need
that much space.

Balance your space requirements with good redundancy and how much data
you can safely back up because stuff happens: hardware fails, power
fails, and you can lose data.

More suggestions:

1. Test some configs for your specific data/environment.

2. Start with smaller mirrored pools, which offer redundancy, good
performance, and more flexibility.

With a SAN, I would assume you are using multiple systems. Did you mean
meta centre or media centre?

3. Consider a mirrored source pool and then create snapshots that you
send to a mirrored backup pool on another system. Mirrored pools can be
easily expanded when you need more space.

4. If you are running a recent OpenSolaris build, you could use the
zpool split command to attach and detach disks from your source pool to
replicate it on another system, in addition to doing more regular
snapshots of source data.

Thanks,

Cindy

On 06/25/10 13:26, Tiernan OToole wrote:
> Good morning all.
> 
>  
> 
> This question has probably poped up before, but maybe not in this exact
way?
> 
>  
> 
> I am planning on building a SAN for my home meta centre, and have some 
> of the raid cards I need for the build. I will be ordering the case 
> soon, and then the drives. The cards I have are 2 8 port PXI-Express 
> cards (A dell Perc 5 and a Adaptec card?). The case will have 20 hot 
> swap SAS/SATA drives, and I will be adding a third RAID controller to 
> allow the full 20 drives.
> 
>  
> 
> I have read something about trying to setup redundancy with the RAID 
> controllers, so having zpools spanning multiple controllers. Given I 
> won?t be using the on-board RAID features of the cards, I am wondering 
> how this should be setup?
> 
>  
> 
> I was thinking of zpools: 2+2+1 X 4 in ZRAID2. This way, I could lose a 
> controller and not lose any data from the pools? But is this theory 
> correct? If I were to use 2Tb drives, each zpool would be 10Tb RAW and 
> 6TB useable? giving me a total of 40Tb RAW and 24Tb usable?
> 
>  
> 
> Is this over kill? Should I be worrying about losing a controller?
> 
>  
> 
> Thanks in advance.
> 
>  
> 
> --Tiernan
> 
> 
> ------------------------------------------------------------------------
> 
> _______________________________________________
> zfs-discuss mailing list
> zfs-discuss at opensolaris.org
> http://mail.opensolaris.org/mailman/listinfo/zfs-discuss

> From: zfs-discuss-bounces at opensolaris.org [mailto:zfs-discuss-
> bounces at opensolaris.org] On Behalf Of Tiernan OToole
> 
> I have read something about trying to setup redundancy with the RAID
> controllers, so having zpools spanning multiple controllers. Given I
> won''t be using the on-board RAID features of the cards, I am
wondering
> how this should be setup.
Option 1:
Suppose you have controllers, A, B, C.
Suppose you have 8 disks per controller, 0, 1, ..., 7
Configure your controller for JBOD mode (so the OS can see each individual
disk) or configure each individual disk as a 1-disk raid0 or raid1, which is
essentially the same as JBOD.  Point is, the OS needs to see each individual
disk.

mirror A0 B0 C0 mirror A1 B1 C1 mirror A2 B2 C2 ...

You will have the total usable capacity of 8 disks, and 16 disks redundancy.

Option 2:

raidz A0 B0 C0 raidz A1 B1 C1 raidz A2 B2 C2 ...

You will have the total usable capacity of 16 disks, and 8 disks redundancy.

Option 3:

If you have any less than 8 disks redundancy, you won''t be protected
against
controller failure.  It''s a calculated risk; a crashed controller would
result in the zpool going offline, and probably an OS crash.  I don''t
know
the probability of data loss in that scenario, but I know none of this
should be a problem if you *do* have the controller redundancy.

> I am planning on building a SAN for my home meta centre, and have some
> of the raid cards I need for the build. I will be ordering the case
> soon, and then the drives. The cards I have are 2 8 port PXI-Express
> cards (A dell Perc 5 and a Adaptec card?). The case will have 20 hot
> swap SAS/SATA drives, and I will be adding a third RAID controller to
> allow the full 20 drives.
First, you won''t need a RAID controller. Just get something cheap with
lots of ports. It''ll suffice - ZFS will do the smart stuff.
> I was thinking of zpools: 2+2+1 X 4 in ZRAID2. This way, I could lose
> a controller and not lose any data from the pools? But is this theory
> correct? If I were to use 2Tb drives, each zpool would be 10Tb RAW and
> 6TB useable? giving me a total of 40Tb RAW and 24Tb usable?
I don''t see the point of using more than one pool. Just use more VDEVs
in the same pool, and redundancy will be just as good as with more pools, and a
single pool is far more flexible.
 
Vennlige hilsener / Best regards

roy
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