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-   -   Using stride on non-RAID (http://www.linux-archive.org/ext3-users/501639-using-stride-non-raid.html)

David Shaw 03-15-2011 09:42 PM

Using stride on non-RAID
 
Hello,

I understand the need for a proper stride setting when formatting a filesystem on a RAID device. However, is there any problem in using a stride setting when formatting a filesystem on a regular non-RAID, non-SSD, just plain-vanilla-single-disk block device? I'm sure there isn't any benefit to it, but I'm curious if there is any harm.

The reason I ask is I'm looking at some code here that can be used on either RAID or non-RAID devices. The stride setting it has is correct for the particular RAID setup it is intended for, but it also uses those settings when formatting a non-RAID device.

David


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Eric Sandeen 03-15-2011 09:53 PM

Using stride on non-RAID
 
On 3/15/11 5:42 PM, David Shaw wrote:
> Hello,
>
> I understand the need for a proper stride setting when formatting a
> filesystem on a RAID device. However, is there any problem in using
> a stride setting when formatting a filesystem on a regular non-RAID,
> non-SSD, just plain-vanilla-single-disk block device? I'm sure there
> isn't any benefit to it, but I'm curious if there is any harm.
>
> The reason I ask is I'm looking at some code here that can be used on
> either RAID or non-RAID devices. The stride setting it has is
> correct for the particular RAID setup it is intended for, but it also
> uses those settings when formatting a non-RAID device.
>
> David

just FWIW, recent kernels & e2fsprogs will just automatically pick
stride based on storage geometry - for md/lvm at least, and for
scsi devices that export this geometry as well.

ext4 has a little stripe-awareness in its allocator; otherwise, stride
just staggers bitmap starts so they don't all end up on the same spindle; [1]
Offhand I don't think it'd cause any harm to set stride on non-raid.

-Eric

[1] ext2fs_allocate_group_table() in lib/ext2fs/alloc_tables.c

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David Shaw 03-16-2011 05:02 PM

Using stride on non-RAID
 
On Mar 15, 2011, at 6:53 PM, Eric Sandeen wrote:

> On 3/15/11 5:42 PM, David Shaw wrote:
>> Hello,
>>
>> I understand the need for a proper stride setting when formatting a
>> filesystem on a RAID device. However, is there any problem in using
>> a stride setting when formatting a filesystem on a regular non-RAID,
>> non-SSD, just plain-vanilla-single-disk block device? I'm sure there
>> isn't any benefit to it, but I'm curious if there is any harm.
>>
>> The reason I ask is I'm looking at some code here that can be used on
>> either RAID or non-RAID devices. The stride setting it has is
>> correct for the particular RAID setup it is intended for, but it also
>> uses those settings when formatting a non-RAID device.
>>
>> David
>
> just FWIW, recent kernels & e2fsprogs will just automatically pick
> stride based on storage geometry - for md/lvm at least, and for
> scsi devices that export this geometry as well.
>
> ext4 has a little stripe-awareness in its allocator; otherwise, stride
> just staggers bitmap starts so they don't all end up on the same spindle; [1]
> Offhand I don't think it'd cause any harm to set stride on non-raid.

Thanks very much for your pointers. It's a nice enhancement that this is done automatically now.

David


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Mag Gam 05-09-2011 10:40 PM

Using stride on non-RAID
 
Are stride settings needed for Hardware RAID devices?

For example, if I do a RAID 5 on a HP-P800 I get a 9.1TB filesystem.
Should I worry about stride in that case?


On Wed, Mar 16, 2011 at 2:02 PM, David Shaw <dshaw@jabberwocky.com> wrote:
> On Mar 15, 2011, at 6:53 PM, Eric Sandeen wrote:
>
>> On 3/15/11 5:42 PM, David Shaw wrote:
>>> Hello,
>>>
>>> I understand the need for a proper stride setting when formatting a
>>> filesystem on a RAID device. *However, is there any problem in using
>>> a stride setting when formatting a filesystem on a regular non-RAID,
>>> non-SSD, just plain-vanilla-single-disk block device? *I'm sure there
>>> isn't any benefit to it, but I'm curious if there is any harm.
>>>
>>> The reason I ask is I'm looking at some code here that can be used on
>>> either RAID or non-RAID devices. *The stride setting it has is
>>> correct for the particular RAID setup it is intended for, but it also
>>> uses those settings when formatting a non-RAID device.
>>>
>>> David
>>
>> just FWIW, recent kernels & e2fsprogs will just automatically pick
>> stride based on storage geometry - for md/lvm at least, and for
>> scsi devices that export this geometry as well.
>>
>> ext4 has a little stripe-awareness in its allocator; otherwise, stride
>> just staggers bitmap starts so they don't all end up on the same spindle; [1]
>> Offhand I don't think it'd cause any harm to set stride on non-raid.
>
> Thanks very much for your pointers. *It's a nice enhancement that this is done automatically now.
>
> David
>
>
> _______________________________________________
> Ext3-users mailing list
> Ext3-users@redhat.com
> https://www.redhat.com/mailman/listinfo/ext3-users
>

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Eric Sandeen 05-09-2011 11:03 PM

Using stride on non-RAID
 
On 5/9/11 5:40 PM, Mag Gam wrote:
> Are stride settings needed for Hardware RAID devices?
>
> For example, if I do a RAID 5 on a HP-P800 I get a 9.1TB filesystem.
> Should I worry about stride in that case?

stride is useful so that you don't end up with metadata hotspots on a single disk. this is true whether the disks are raided together in hardware or in software, I think.

-Eric

>
> On Wed, Mar 16, 2011 at 2:02 PM, David Shaw <dshaw@jabberwocky.com> wrote:
>> On Mar 15, 2011, at 6:53 PM, Eric Sandeen wrote:
>>
>>> On 3/15/11 5:42 PM, David Shaw wrote:
>>>> Hello,
>>>>
>>>> I understand the need for a proper stride setting when formatting a
>>>> filesystem on a RAID device. However, is there any problem in using
>>>> a stride setting when formatting a filesystem on a regular non-RAID,
>>>> non-SSD, just plain-vanilla-single-disk block device? I'm sure there
>>>> isn't any benefit to it, but I'm curious if there is any harm.
>>>>
>>>> The reason I ask is I'm looking at some code here that can be used on
>>>> either RAID or non-RAID devices. The stride setting it has is
>>>> correct for the particular RAID setup it is intended for, but it also
>>>> uses those settings when formatting a non-RAID device.
>>>>
>>>> David
>>>
>>> just FWIW, recent kernels & e2fsprogs will just automatically pick
>>> stride based on storage geometry - for md/lvm at least, and for
>>> scsi devices that export this geometry as well.
>>>
>>> ext4 has a little stripe-awareness in its allocator; otherwise, stride
>>> just staggers bitmap starts so they don't all end up on the same spindle; [1]
>>> Offhand I don't think it'd cause any harm to set stride on non-raid.
>>
>> Thanks very much for your pointers. It's a nice enhancement that this is done automatically now.
>>
>> David
>>
>>
>> _______________________________________________
>> Ext3-users mailing list
>> Ext3-users@redhat.com
>> https://www.redhat.com/mailman/listinfo/ext3-users
>>

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