[Lustre-devel] Control file striping

[Kalyana C]

I will need to setup striping on specific OSTs on demand. Its not a fixed
setup.

Here is what I am thinking, with my current understanding:

*) user app sends the details (OST ids, name of the pool) to a listener on
MGS
*) a process on MGS executes the command and sends back an ack
*) user app sets up striping on the newly created pool
*) pool is deleted once striping is set

I was hoping to find out if there was a better (and easier) way to do this.

A simple usage case is as follows:
There are a mix of disks with varying performance in the file system.
Depending on the application, I would like to change the disks used for
that instance. Say, 10% spindle, 90% SSD, 50-50 for another etc.

The same can be applied to a mix of storage devices in the same file system
- disks with varying levels of redundancy or even varying devices.

Regards,
Kalyan

On Mon, Nov 5, 2012 at 12:16 PM, White, Cliff <cliff.white at intel.com> wrote:

>  Creating/destroying pools must be done as per the manual, from MDS.
> Do you need to frequently create/destroy pools, or would you have a fixed
> setup?
>
>  The normal method is to map various pools (and other striping policies)
> to directories, then user space applications
> can access specific pools by pointing at the requisite directory, thus
> requiring no special API.
> Once pools are created, the directory creation/striping is all done on a
> client via lfs setstripe, the liblustreapi can
> also be used by clients to set striping via C calls.
>
>  Best
> cliffw
>
>
>  On Nov 5, 2012, at 10:01 AM, Kalyana C <ckkccf at gmail.com>
>  wrote:
>
>  > Have you considered using a combination of OST Pools and striping
> fit your needs?
>
>  This is the only way possible that I currently know of.
>
>  But is it possible to manage OST pools via an API call? Can it be done
> from a client under a normal user application? Or does it have the same
> restrictions as described at
> http://wiki.lustre.org/index.php/Creating_and_Managing_OST_Pools
>
>  Regards,
> Kalyan
>
> On Mon, Nov 5, 2012 at 11:57 AM, Ben Evans <Ben.Evans at terascala.com>wrote:
>
>> Have you considered using a combination of OST Pools and striping fit
>> your needs?
>>
>> -----Original Message-----
>> From: lustre-devel-bounces at lists.lustre.org
>> [mailto:lustre-devel-bounces at lists.lustre.org] On Behalf Of Atchley,
>> Scott
>> Sent: Monday, November 05, 2012 12:47 PM
>> To: Kalyana C
>> Cc: lustre-devel at lists.lustre.org
>> Subject: Re: [Lustre-devel] Control file striping
>>
>> On Nov 3, 2012, at 1:41 PM, Kalyana C <ckkccf at gmail.com> wrote:
>>
>> > Hello,
>> >
>> > I am trying to figure out a way to:
>> >
>> > set striping across a set of OSTs of my choice.
>> >
>> > lfs setstripe command and API call does not allow for this currently.
>> The user can only set the starting OST through the index parameter. I
>> appreciate why there is no such feature currently; you do not want to
>> let the users have control on how OSTs are used since it can result in
>> OST usage imbalance.
>> >
>> > However, I do have a valid usage case for such a feature and I am
>> trying to figure out the best way to do it.
>>
>> I have a valid use for it as well. It would be nice to have this feature
>> back.
>>
>> Scott
>>
>> >
>> > One way to achieve the same result is through the use of OST pools.
>> However, the userland tools do not work from a client node, it has to be
>> run on the MGS. There are also other restrictions as described here:
>> http://wiki.lustre.org/index.php/Creating_and_Managing_OST_Pools
>> >
>> > I am also digging through the Lustre source and header files to see if
>> there are other (undocumented) ways to do this.
>> >
>> > So, my questions are as follows:
>> >
>> > 1) Is there currently a way for a user to control the striping of a
>> file / directory on a selected set of OSTs? If yes, is it possible to do
>> it through an API call or a command line utility?
>> >
>> > 2) If answer to (1) is No, Is there a way to do this with admin rights
>> from the MDS or client nodes?
>> >
>> > 3) If pools are the only way to achieve this, is there an API call to
>> create, manage and destroy pools from a user application? Is there any
>> impact on performance of MDS components if pools are dynamically created
>> and deleted on demand? Can the API be called from a client node (root or
>> user) or does it have to be on the MGS?
>> >
>> > Thank you.
>> >
>> > Regards,
>> > Kalyana Chadalavada
>> >
>> > _______________________________________________
>> > Lustre-devel mailing list
>> > Lustre-devel at lists.lustre.org
>> > http://lists.lustre.org/mailman/listinfo/lustre-devel
>>
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