maximum size

maximum size

[Farkas Levente]

hi,
i'd been already asked, but don't get any answer. what is the maximum 
size of a raid5 and raid5 partition in kerenel 2.6? i try to find the 
answer but found only kernel 2.4 info.
thanks in advance.

-- 
   Levente                               "Si vis pacem para bellum!"

Re: maximum size

[Brad Campbell]

Farkas Levente wrote:
> hi,
> i'd been already asked, but don't get any answer. what is the maximum 
> size of a raid5 and raid5 partition in kerenel 2.6? i try to find the 
> answer but found only kernel 2.4 info.
> thanks in advance.

Don't know about max sizes, but I have a 2.1TB raid-5 and a 3TB raid-6 here. No issues at all.
Had to move to 2.6 as 2.4 did not support > 2TB filesystems

Brad
-- 
"Human beings, who are almost unique in having the ability
to learn from the experience of others, are also remarkable
for their apparent disinclination to do so." -- Douglas Adams

Re: maximum size

[Neil Brown]

On Tuesday September 27, lfarkas@bppiac.hu wrote:
> hi,
> i'd been already asked, but don't get any answer. what is the maximum 
> size of a raid5 and raid5 partition in kerenel 2.6? i try to find the 
> answer but found only kernel 2.4 info.
> thanks in advance.
> 

Providing you are using either 64bit hardware, or the 'LBD' (large
block device) config, then raid5 arrays can be up to 2^64 -
i.e. enormous - no practical limit.

I don't know what you mean by 'raid5 partition'.  If you mean like a
regular partition of a device, then the partition can be nearly as bit
as the array....

Component devices in a raid5 cannot be larger than 2 terabytes, but I
don't think you can buy devices that big yet.

NeilBrown

Re: maximum size

[Farkas Levente]

Neil Brown wrote:
> On Tuesday September 27, lfarkas@bppiac.hu wrote:
> 
>>hi,
>>i'd been already asked, but don't get any answer. what is the maximum 
>>size of a raid5 and raid5 partition in kerenel 2.6? i try to find the 
>>answer but found only kernel 2.4 info.
>>thanks in advance.
>>
> 
> 
> Providing you are using either 64bit hardware, or the 'LBD' (large
> block device) config, then raid5 arrays can be up to 2^64 -
> i.e. enormous - no practical limit.

huu, i don't know. we use 3ware 7506 controller. on it onw homepage it 
said:
---------------------------
Supports up to 12 drives with a single PCI card enabling up to 3.6 
terabytes of storage (dependent on drive capacity, 2TB per array maximum)
---------------------------
but it's all about the hardware raid5. so it's native hardware raid5 
can't be larger than 2TB.
and another quote:
---------------------------
PCI 2.2 compliant 64-bit / 66MHz bus master (2-port controllers are
32-bit / 66MHz PCI compliant)
---------------------------
but it's the pci bus interface not the device.
and as we use in jbod mode there is no info about it. and i read again 
the spec but can't find any info about it.

> I don't know what you mean by 'raid5 partition'.  If you mean like a
> regular partition of a device, then the partition can be nearly as bit
> as the array....

suppose i create the raid device with:
mdadm --create /dev/md0--level=5 --raid-devices=8 --spare-devices=1 
/dev/sd[abcdefgh]1
then what is the maximum size for /dev/md0?
(or more precisely after a mkfs.ext3 /dev/md0).
yours.

-- 
   Levente                               "Si vis pacem para bellum!"

Re: maximum size

[Brad Dameron]

On Tue, 2005-09-27 at 15:21 +0200, Farkas Levente wrote:
> hi,
> i'd been already asked, but don't get any answer. what is the maximum 
> size of a raid5 and raid5 partition in kerenel 2.6? i try to find the 
> answer but found only kernel 2.4 info.
> thanks in advance.
> 

It depends on what FS you are using as well as if you are doing a
software or hardware RAID. With software on a Reiser or XFS it is very
very large. On hardware there is usually a controller limitation. I
currently have a 3TB partition with Reiser 3 in a RAID5 on a 3ware
9500S-12. However to get this size partition you have to use parted
instead of fdisk to create it. Otherwise the largest you will see is
700MB. 

Brad Dameron
SeaTab Software
www.seatab.com

Re: maximum size

[Neil Brown]

On Tuesday September 27, lfarkas@bppiac.hu wrote:
> Neil Brown wrote:
> > On Tuesday September 27, lfarkas@bppiac.hu wrote:
> > 
> >>hi,
> >>i'd been already asked, but don't get any answer. what is the maximum 
> >>size of a raid5 and raid5 partition in kerenel 2.6? i try to find the 
> >>answer but found only kernel 2.4 info.
> >>thanks in advance.
> >>
> > 
> > 
> > Providing you are using either 64bit hardware, or the 'LBD' (large
> > block device) config, then raid5 arrays can be up to 2^64 -
> > i.e. enormous - no practical limit.
> 
> huu, i don't know. we use 3ware 7506 controller. on it onw homepage it 
> said:
> ---------------------------
> Supports up to 12 drives with a single PCI card enabling up to 3.6 
> terabytes of storage (dependent on drive capacity, 2TB per array maximum)
> ---------------------------
> but it's all about the hardware raid5. so it's native hardware raid5 
> can't be larger than 2TB.

Quite possibly.  I was talking about 'md' software raid.  It don't not
have a 2TB limit in 2.6

> > I don't know what you mean by 'raid5 partition'.  If you mean like a
> > regular partition of a device, then the partition can be nearly as bit
> > as the array....
> 
> suppose i create the raid device with:
> mdadm --create /dev/md0--level=5 --raid-devices=8 --spare-devices=1 
> /dev/sd[abcdefgh]1
> then what is the maximum size for /dev/md0?
> (or more precisely after a mkfs.ext3 /dev/md0).

The /dev/sdX1 cannot be larger than 2TB.  The /dev/md0 can be as big
as you like.  The filesystem can be as big as your filesystem allows.
I don't think ext3 can exceed 2 TB (I could be wrong).  Other
filesystems (reiser, xfs) can certainly use whatever you can through
at them.

NeilBrown

Re: maximum size

[Joshua Baker-LePain]

On Wed, 28 Sep 2005 at 10:56am, Neil Brown wrote

> On Tuesday September 27, lfarkas@bppiac.hu wrote:

>> suppose i create the raid device with:
>> mdadm --create /dev/md0--level=5 --raid-devices=8 --spare-devices=1
>> /dev/sd[abcdefgh]1
>> then what is the maximum size for /dev/md0?
>> (or more precisely after a mkfs.ext3 /dev/md0).
>
> The /dev/sdX1 cannot be larger than 2TB.  The /dev/md0 can be as big
> as you like.  The filesystem can be as big as your filesystem allows.
> I don't think ext3 can exceed 2 TB (I could be wrong).  Other

RH (e.g.) officially supports ext3 FSs up to 8TB in RHEL4.

-- 
Joshua Baker-LePain
Department of Biomedical Engineering
Duke University

Re: maximum size

[Brad Campbell]

Neil Brown wrote:
> I don't think ext3 can exceed 2 TB (I could be wrong).  Other

I have a 3TB ext3 on a raid-6 md here. 2.6.10

Regards,
Brad
-- 
"Human beings, who are almost unique in having the ability
to learn from the experience of others, are also remarkable
for their apparent disinclination to do so." -- Douglas Adams

Re: maximum size

[Neil Brown]

On Wednesday September 28, jlb17@duke.edu wrote:
> On Wed, 28 Sep 2005 at 10:56am, Neil Brown wrote
> 
> > On Tuesday September 27, lfarkas@bppiac.hu wrote:
> 
> >> suppose i create the raid device with:
> >> mdadm --create /dev/md0--level=5 --raid-devices=8 --spare-devices=1
> >> /dev/sd[abcdefgh]1
> >> then what is the maximum size for /dev/md0?
> >> (or more precisely after a mkfs.ext3 /dev/md0).
> >
> > The /dev/sdX1 cannot be larger than 2TB.  The /dev/md0 can be as big
> > as you like.  The filesystem can be as big as your filesystem allows.
> > I don't think ext3 can exceed 2 TB (I could be wrong).  Other
> 
> RH (e.g.) officially supports ext3 FSs up to 8TB in RHEL4.

See... I was wrong!  :-)

I'm sure there is a 32bit limit somewhere, so it's probably that block
addresses are limited to 32 bits.  With 4K blocks, that's 2^34 K, or
16TB.... Maybe there is some confusion with the sign bit, making it on
2^33K, or 8TB.

NeilBrown

Re: maximum size

[Farkas Levente]

Neil Brown wrote:
> On Wednesday September 28, jlb17@duke.edu wrote:
> 
>>On Wed, 28 Sep 2005 at 10:56am, Neil Brown wrote
>>
>>
>>>On Tuesday September 27, lfarkas@bppiac.hu wrote:
>>
>>>>suppose i create the raid device with:
>>>>mdadm --create /dev/md0--level=5 --raid-devices=8 --spare-devices=1
>>>>/dev/sd[abcdefgh]1
>>>>then what is the maximum size for /dev/md0?
>>>>(or more precisely after a mkfs.ext3 /dev/md0).
>>>
>>>The /dev/sdX1 cannot be larger than 2TB.  The /dev/md0 can be as big
>>>as you like.  The filesystem can be as big as your filesystem allows.
>>>I don't think ext3 can exceed 2 TB (I could be wrong).  Other
>>
>>RH (e.g.) officially supports ext3 FSs up to 8TB in RHEL4.
> 
> 
> See... I was wrong!  :-)
> 
> I'm sure there is a 32bit limit somewhere, so it's probably that block
> addresses are limited to 32 bits.  With 4K blocks, that's 2^34 K, or
> 16TB.... Maybe there is some confusion with the sign bit, making it on
> 2^33K, or 8TB.

i already find the trivial source kernel/Documentation/filesystems/ext2.txt:
---------------------------------
Filesystem block size:     1kB        2kB        4kB        8kB

File size limit:          16GB      256GB     2048GB     2048GB
Filesystem size limit:  2047GB     8192GB    16384GB    32768GB
---------------------------------


-- 
   Levente                               "Si vis pacem para bellum!"