Using stride on non-RAID

[Eric Sandeen]

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 at 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
>>
>>
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