* XFS sunit/swidth for raid10
@ 2007-03-21 23:23 Peter Rabbitson
2007-03-22 8:23 ` dean gaudet
0 siblings, 1 reply; 6+ messages in thread
From: Peter Rabbitson @ 2007-03-21 23:23 UTC (permalink / raw)
To: linux-raid
Hi,
How does one determine the XFS sunit and swidth sizes for a software
raid10 with 3 copies?
Thanks
Peter
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: XFS sunit/swidth for raid10
2007-03-21 23:23 XFS sunit/swidth for raid10 Peter Rabbitson
@ 2007-03-22 8:23 ` dean gaudet
2007-03-22 12:05 ` Peter Rabbitson
0 siblings, 1 reply; 6+ messages in thread
From: dean gaudet @ 2007-03-22 8:23 UTC (permalink / raw)
To: Peter Rabbitson; +Cc: linux-raid
On Thu, 22 Mar 2007, Peter Rabbitson wrote:
> Hi,
> How does one determine the XFS sunit and swidth sizes for a software raid10
> with 3 copies?
mkfs.xfs uses the GET_ARRAY_INFO ioctl to get the data it needs from
software raid and select an appropriate sunit/swidth...
although i'm not sure i agree entirely with its choice for raid10:
*sunit = md.chunk_size >> 9;
*swidth = *sunit * md.raid_disks;
i'd think it would depend on the layout of the raid10 (near, far,
offset)... for near2 on 4 disks i'd expect swidth to be only 2*sunit...
but for far2 on 4 disks i'd expect 4*sunit... but i'm not sure. it
probably doesn't matter.
-dean
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: XFS sunit/swidth for raid10
2007-03-22 8:23 ` dean gaudet
@ 2007-03-22 12:05 ` Peter Rabbitson
2007-03-23 6:48 ` dean gaudet
0 siblings, 1 reply; 6+ messages in thread
From: Peter Rabbitson @ 2007-03-22 12:05 UTC (permalink / raw)
To: linux-raid
dean gaudet wrote:
> On Thu, 22 Mar 2007, Peter Rabbitson wrote:
>
>> Hi,
>> How does one determine the XFS sunit and swidth sizes for a software raid10
>> with 3 copies?
>
> mkfs.xfs uses the GET_ARRAY_INFO ioctl to get the data it needs from
> software raid and select an appropriate sunit/swidth...
>
> although i'm not sure i agree entirely with its choice for raid10:
So do I, especially as it makes no checks for the amount of copies (3 in
my case, not 2).
>it probably doesn't matter.
This was essentially my question. For an array -pf3 -c1024 I get swidth
= 4 * sunit = 4MiB. Is it about right and does it matter at all?
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: XFS sunit/swidth for raid10
2007-03-22 12:05 ` Peter Rabbitson
@ 2007-03-23 6:48 ` dean gaudet
2007-03-23 8:20 ` Peter Rabbitson
0 siblings, 1 reply; 6+ messages in thread
From: dean gaudet @ 2007-03-23 6:48 UTC (permalink / raw)
To: Peter Rabbitson; +Cc: linux-raid
On Thu, 22 Mar 2007, Peter Rabbitson wrote:
> dean gaudet wrote:
> > On Thu, 22 Mar 2007, Peter Rabbitson wrote:
> >
> > > Hi,
> > > How does one determine the XFS sunit and swidth sizes for a software
> > > raid10
> > > with 3 copies?
> >
> > mkfs.xfs uses the GET_ARRAY_INFO ioctl to get the data it needs from
> > software raid and select an appropriate sunit/swidth...
> >
> > although i'm not sure i agree entirely with its choice for raid10:
>
> So do I, especially as it makes no checks for the amount of copies (3 in my
> case, not 2).
>
> > it probably doesn't matter.
>
> This was essentially my question. For an array -pf3 -c1024 I get swidth = 4 *
> sunit = 4MiB. Is it about right and does it matter at all?
how many drives?
-dean
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: XFS sunit/swidth for raid10
2007-03-23 6:48 ` dean gaudet
@ 2007-03-23 8:20 ` Peter Rabbitson
2007-03-25 19:16 ` dean gaudet
0 siblings, 1 reply; 6+ messages in thread
From: Peter Rabbitson @ 2007-03-23 8:20 UTC (permalink / raw)
To: linux-raid
dean gaudet wrote:
> On Thu, 22 Mar 2007, Peter Rabbitson wrote:
>
>> dean gaudet wrote:
>>> On Thu, 22 Mar 2007, Peter Rabbitson wrote:
>>>
>>>> Hi,
>>>> How does one determine the XFS sunit and swidth sizes for a software
>>>> raid10
>>>> with 3 copies?
>>> mkfs.xfs uses the GET_ARRAY_INFO ioctl to get the data it needs from
>>> software raid and select an appropriate sunit/swidth...
>>>
>>> although i'm not sure i agree entirely with its choice for raid10:
>> So do I, especially as it makes no checks for the amount of copies (3 in my
>> case, not 2).
>>
>>> it probably doesn't matter.
>> This was essentially my question. For an array -pf3 -c1024 I get swidth = 4 *
>> sunit = 4MiB. Is it about right and does it matter at all?
>
> how many drives?
>
Sorry. 4 drives, 3 far copies (so any 2 drives can fail), 1M chunk.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: XFS sunit/swidth for raid10
2007-03-23 8:20 ` Peter Rabbitson
@ 2007-03-25 19:16 ` dean gaudet
0 siblings, 0 replies; 6+ messages in thread
From: dean gaudet @ 2007-03-25 19:16 UTC (permalink / raw)
To: Peter Rabbitson; +Cc: linux-raid
On Fri, 23 Mar 2007, Peter Rabbitson wrote:
> dean gaudet wrote:
> > On Thu, 22 Mar 2007, Peter Rabbitson wrote:
> >
> > > dean gaudet wrote:
> > > > On Thu, 22 Mar 2007, Peter Rabbitson wrote:
> > > >
> > > > > Hi,
> > > > > How does one determine the XFS sunit and swidth sizes for a software
> > > > > raid10
> > > > > with 3 copies?
> > > > mkfs.xfs uses the GET_ARRAY_INFO ioctl to get the data it needs from
> > > > software raid and select an appropriate sunit/swidth...
> > > >
> > > > although i'm not sure i agree entirely with its choice for raid10:
> > > So do I, especially as it makes no checks for the amount of copies (3 in
> > > my
> > > case, not 2).
> > >
> > > > it probably doesn't matter.
> > > This was essentially my question. For an array -pf3 -c1024 I get swidth =
> > > 4 *
> > > sunit = 4MiB. Is it about right and does it matter at all?
> >
> > how many drives?
> >
>
> Sorry. 4 drives, 3 far copies (so any 2 drives can fail), 1M chunk.
my mind continues to be blown by linux raid10.
so that's like raid1 on 4 disks except the copies are offset by 1/4th of
the disk?
i think swidth = 4*sunit is the right config then -- 'cause a read of 4MiB
will stride all 4 disks...
-dean
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2007-03-25 19:16 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2007-03-21 23:23 XFS sunit/swidth for raid10 Peter Rabbitson
2007-03-22 8:23 ` dean gaudet
2007-03-22 12:05 ` Peter Rabbitson
2007-03-23 6:48 ` dean gaudet
2007-03-23 8:20 ` Peter Rabbitson
2007-03-25 19:16 ` dean gaudet
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.