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"Benoit St-Pierre" 08-27-2008 07:49 PM

RAID with mixed drive sizes
 
I though you can have up to 255 partitions/drive. The partitions would
be in a RAID array so I wouldn't have to deal with them directly anyway.

On Wed, Aug 27, 2008 at 3:20 PM, Xav' <xp@linuxant.fr> wrote:

On Wednesday 27 August 2008 21:00:11 Benoit St-Pierre, you wrote*:



> I'm in the planning stages of setting up a file server and am considering

> using RAID.

>

> My concern is that my drive sizes are mixed. I have two 500GB SATA drives,

> a 320GB IDE and a 250GB IDE.

>

> I would like to set these up so that the maximum amount of disk space is

> usable, but still be able to recover from any one drive failing. I would

> also like to be able to add drives of any size as easily as possible.

>

> Is it possible to split each disk into a bunch of 10GB partitions, giving

> me 157 partitions in total, and specifying that I want to have 50

> partitions worth of parity info so that if any 50 partitions go bad (ie:

> one of the 500GB disks) the RAID can recover? Adding/replacing would be

> simple if I can change the amount of parity info to keep, but I don't know

> if this is actually possible. It looks as though spares need to be

> explicitly given so, if a disk with lots of spares goes down, it's not

> going to work.



AFAIK, it's not possible to have so much partitions under linux, but i can't

remember the maximum of supported partitions... but good luck to manage a so

wide number of partitions !*



> Another option I see is if I create 4x 250GB partitions (one on each drive)

> in one RAID5 array, 3x 70GB partitions (on the 3 larger drives) in another

> RAID5 array, and two 120GB in a RAID1 array. The RAID1 array reduces my

> total available disk space a bit, which is less than ideal and

> adding/replacing disks would be more of a headache.



IMHO, i think this could be a solution. This is possible using software RAID as

it's in the kernel, and then reassemble created raid partitions in one LVM

volume group, so you can use partitions of any space !



> I remember reading something about using LVM and RAID to achieve this, but

> everything I've found has been for identical drives.

>

> Any suggestions?



HTH.



Xavier Parizet

Neil Bothwick 08-27-2008 08:01 PM

RAID with mixed drive sizes
 
On Wed, 27 Aug 2008 15:00:11 -0400, Benoit St-Pierre wrote:

> I'm in the planning stages of setting up a file server and am
> considering using RAID.
>
> My concern is that my drive sizes are mixed. I have two 500GB SATA
> drives, a 320GB IDE and a 250GB IDE.
>
> I would like to set these up so that the maximum amount of disk space is
> usable, but still be able to recover from any one drive failing. I would
> also like to be able to add drives of any size as easily as possible.

Create one 500GB RAID1 array with the SATA drives, then create a 250GB
array using the IDE drives. Only 80GB lost, which you could partition out
and use separately if you really need to.

You want something you can easily recover from in the event of a disk
failure, so keep it simple.


--
Neil Bothwick

Loose bits sink chips.

Xav' 08-27-2008 08:03 PM

RAID with mixed drive sizes
 
On Wednesday 27 August 2008 21:49:22 Benoit St-Pierre, you wrote*:
> I though you can have up to 255 partitions/drive. The partitions would be
> in a RAID array so I wouldn't have to deal with them directly anyway.

After little googling, it seems that the number of logical partitions may be
unlimited as it is organized like chained lists, each logical partitions
indicating the size of the following... but under linux, the number of
partitions for an IDE drive is limited to 63 while for SCSI one it's 15. Maybe
these limits were over, but i don't know enough about linux disk management to
say anything more...

> On Wed, Aug 27, 2008 at 3:20 PM, Xav' <xp@linuxant.fr> wrote:
> > On Wednesday 27 August 2008 21:00:11 Benoit St-Pierre, you wrote :
> > > I'm in the planning stages of setting up a file server and am
> > > considering using RAID.
> > >
> > > My concern is that my drive sizes are mixed. I have two 500GB SATA
> >
> > drives,
> >
> > > a 320GB IDE and a 250GB IDE.
> > >
> > > I would like to set these up so that the maximum amount of disk space
> > > is usable, but still be able to recover from any one drive failing. I
> > > would also like to be able to add drives of any size as easily as
> > > possible.
> > >
> > > Is it possible to split each disk into a bunch of 10GB partitions,
> > > giving me 157 partitions in total, and specifying that I want to have
> > > 50 partitions worth of parity info so that if any 50 partitions go bad
> > > (ie: one of the 500GB disks) the RAID can recover? Adding/replacing
> > > would be simple if I can change the amount of parity info to keep, but
> > > I don't
> >
> > know
> >
> > > if this is actually possible. It looks as though spares need to be
> > > explicitly given so, if a disk with lots of spares goes down, it's not
> > > going to work.
> >
> > AFAIK, it's not possible to have so much partitions under linux, but i
> > can't
> > remember the maximum of supported partitions... but good luck to manage a
> > so
> > wide number of partitions !
> >
> > > Another option I see is if I create 4x 250GB partitions (one on each
> >
> > drive)
> >
> > > in one RAID5 array, 3x 70GB partitions (on the 3 larger drives) in
> >
> > another
> >
> > > RAID5 array, and two 120GB in a RAID1 array. The RAID1 array reduces my
> > > total available disk space a bit, which is less than ideal and
> > > adding/replacing disks would be more of a headache.
> >
> > IMHO, i think this could be a solution. This is possible using software
> > RAID as
> > it's in the kernel, and then reassemble created raid partitions in one
> > LVM volume group, so you can use partitions of any space !
> >
> > > I remember reading something about using LVM and RAID to achieve this,
> >
> > but
> >
> > > everything I've found has been for identical drives.
> > >
> > > Any suggestions?
> >
> > HTH.
> >
> > Xavier Parizet

"Benoit St-Pierre" 08-27-2008 08:07 PM

RAID with mixed drive sizes
 
On Wed, Aug 27, 2008 at 4:01 PM, Neil Bothwick <neil@digimed.co.uk> wrote:

On Wed, 27 Aug 2008 15:00:11 -0400, Benoit St-Pierre wrote:



> I'm in the planning stages of setting up a file server and am

> considering using RAID.

>

> My concern is that my drive sizes are mixed. I have two 500GB SATA

> drives, a 320GB IDE and a 250GB IDE.

>

> I would like to set these up so that the maximum amount of disk space is

> usable, but still be able to recover from any one drive failing. I would

> also like to be able to add drives of any size as easily as possible.



Create one 500GB RAID1 array with the SATA drives, then create a 250GB

array using the IDE drives. Only 80GB lost, which you could partition out

and use separately if you really need to.



You want something you can easily recover from in the event of a disk

failure, so keep it simple.





--

Neil Bothwick



Loose bits sink chips.
This is a _much_ larger loss. With RAID5 I can use 2/3 of my storage space. RAID1 I can only use half.

"Benoit St-Pierre" 08-27-2008 08:09 PM

RAID with mixed drive sizes
 
On Wed, Aug 27, 2008 at 4:03 PM, Xav' <xp@linuxant.fr> wrote:

On Wednesday 27 August 2008 21:49:22 Benoit St-Pierre, you wrote*:

> I though you can have up to 255 partitions/drive. The partitions would be

> in a RAID array so I wouldn't have to deal with them directly anyway.



After little googling, it seems that the number of logical partitions may be

unlimited as it is organized like chained lists, each logical partitions

indicating the size of the following... but under linux, the number of

partitions for an IDE drive is limited to 63 while for SCSI one it's 15. Maybe

these limits were over, but i don't know enough about linux disk management to

say anything more...



> On Wed, Aug 27, 2008 at 3:20 PM, Xav' <xp@linuxant.fr> wrote:

> > On Wednesday 27 August 2008 21:00:11 Benoit St-Pierre, you wrote :

> > > I'm in the planning stages of setting up a file server and am

> > > considering using RAID.

> > >

> > > My concern is that my drive sizes are mixed. I have two 500GB SATA

> >

> > drives,

> >

> > > a 320GB IDE and a 250GB IDE.

> > >

> > > I would like to set these up so that the maximum amount of disk space

> > > is usable, but still be able to recover from any one drive failing. I

> > > would also like to be able to add drives of any size as easily as

> > > possible.

> > >

> > > Is it possible to split each disk into a bunch of 10GB partitions,

> > > giving me 157 partitions in total, and specifying that I want to have

> > > 50 partitions worth of parity info so that if any 50 partitions go bad

> > > (ie: one of the 500GB disks) the RAID can recover? Adding/replacing

> > > would be simple if I can change the amount of parity info to keep, but

> > > I don't

> >

> > know

> >

> > > if this is actually possible. It looks as though spares need to be

> > > explicitly given so, if a disk with lots of spares goes down, it's not

> > > going to work.

> >

> > AFAIK, it's not possible to have so much partitions under linux, but i

> > can't

> > remember the maximum of supported partitions... but good luck to manage a

> > so

> > wide number of partitions !

> >

> > > Another option I see is if I create 4x 250GB partitions (one on each

> >

> > drive)

> >

> > > in one RAID5 array, 3x 70GB partitions (on the 3 larger drives) in

> >

> > another

> >

> > > RAID5 array, and two 120GB in a RAID1 array. The RAID1 array reduces my

> > > total available disk space a bit, which is less than ideal and

> > > adding/replacing disks would be more of a headache.

> >

> > IMHO, i think this could be a solution. This is possible using software

> > RAID as

> > it's in the kernel, and then reassemble created raid partitions in one

> > LVM volume group, so you can use partitions of any space !

> >

> > > I remember reading something about using LVM and RAID to achieve this,

> >

> > but

> >

> > > everything I've found has been for identical drives.

> > >

> > > Any suggestions?

> >

> > HTH.

> >

> > Xavier Parizet







Yeah, it looks like 15 partitions is the max for SATA/SCSI drives, darn.

Florian Philipp 08-27-2008 08:29 PM

RAID with mixed drive sizes
 
Benoit St-Pierre schrieb:

I'm in the planning stages of setting up a file server and am considering
using RAID.

My concern is that my drive sizes are mixed. I have two 500GB SATA drives, a
320GB IDE and a 250GB IDE.

I would like to set these up so that the maximum amount of disk space is
usable, but still be able to recover from any one drive failing. I would
also like to be able to add drives of any size as easily as possible.



I can think of two ways:

1. RAID1 over those 2 SATAs + RAID1 over the IDEs, then an LVM on top of
both.
This wastes 70GB and uses a total of 750GB for redundancy. New disks can
be added in increments of two (forming a new RAID1 which is then added
to the LVM volume group)


2. Linear or RAID0-arrangement over the two IDEs, RAID5 over this RAID
and the other two disks.

This wastes 70GB, too and uses a total of 500GB for redundancy.

Note1: NEVER EVER build some kind of RAID other than "Linear" (also
called JBOD) over two IDE disks on the same cable. Performance will
suffer greatly as will security because most simple onboard controllers
can't handle a dying disk and that one might take the other one with it
into death.


Note2: RAID-autodetection doesn't always work with RAIDs over RAIDs. It
is better to deactivate RAID-autodetection and tell the kernel directly
which devices shall be created in which order. See:
/usr/src/linux/Documentation/md.txt

Stroller 08-28-2008 09:11 AM

RAID with mixed drive sizes
 
On 27 Aug 2008, at 20:00, Benoit St-Pierre wrote:

...
I have two 500GB SATA drives, a 320GB IDE and a 250GB IDE.
...
I would like to set these up so that the maximum amount of disk
space is usable, but still be able to recover from any one drive
failing. I would also like to be able to add drives of any size as
easily as possible.


Cheap, fast & purty - pick any two.

What you're suggesting is at best a headache & more likely a complete
nightmare, just waiting to happen.


I can see that you have over 500GB of EIDE, so in the ideal world you
"should" be able to use that as the parity for your 2 x 500GB of SATA
drives.


But in the real world, spend 35.25 and get a 3rd 500GB SATA.

Use the EIDE for swap or non-redundant files or something.

Hard-drives from the "scrap" pile can be immensely useful, but if you
want ease of setup, reliability, redundancy and peace-of-mind then
scratch "cheap" off your list of requirements. Drives are cheap these
days, particularly 500GB ones right now.


Stroller.

Neil Bothwick 08-28-2008 09:24 AM

RAID with mixed drive sizes
 
On Thu, 28 Aug 2008 10:11:48 +0100, Stroller wrote:

> Hard-drives from the "scrap" pile can be immensely useful, but if you
> want ease of setup, reliability, redundancy and peace-of-mind then
> scratch "cheap" off your list of requirements.

As the saying goes "Cheap, reliable, fast - pick any two".


--
Neil Bothwick

WinErr 006: Malicious error - Desqview found on drive

Stroller 08-28-2008 09:53 AM

RAID with mixed drive sizes
 
On 28 Aug 2008, at 10:24, Neil Bothwick wrote:


On Thu, 28 Aug 2008 10:11:48 +0100, Stroller wrote:


Hard-drives from the "scrap" pile can be immensely useful, but if you
want ease of setup, reliability, redundancy and peace-of-mind then
scratch "cheap" off your list of requirements.


As the saying goes "Cheap, reliable, fast - pick any two".


I did open my message with the words "cheap, fast & purty" - it all
depends what you're buying. ;)


Stroller.

Neil Bothwick 08-28-2008 10:15 AM

RAID with mixed drive sizes
 
On Thu, 28 Aug 2008 10:53:16 +0100, Stroller wrote:

> I did open my message with the words "cheap, fast & purty"

Sorry, I missed that.

> - it all depends what you're buying. ;)

I think we'll end this conversation right here :)


--
Neil Bothwick

Is it possible to be totally partial?


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