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

[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

[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!"

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

[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