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Subject: Re: Can we setup pNFS with multiple DSs ?
To:     Benjamin Coddington <bcodding@redhat.com>
Cc:     linux-nfs@vger.kernel.org
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 <28D4997E-0B02-4979-9DE3-7E87A7FD7BA1@redhat.com>
From:   Jianchao Wang <jianchao.wan9@gmail.com>
Message-ID: <f4e71030-85a4-1e93-9e29-9ebf92260b12@gmail.com>
Date:   Thu, 13 Jun 2019 15:03:31 +0800
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Hi Ben

Thanks so much for your kindly reply.

On 2019/6/12 20:07, Benjamin Coddington wrote:
> Hi Jianchao,
> 
> On 12 Jun 2019, at 3:55, Jianchao Wang wrote:
> 
>> Hi
>>
>> I'm trying to setup a pNFS experiment environment.
>> And this is what I have got,
>> VM-0 (DS)      running a iscsi target
>> VM-1 (MS)      initiator, mount a XFS on the device, and export it by NFS with pnfs option
>> VM-2 (Client)  initiator, but not mount, running a blkmapd
>>                mount the shared directory of VM-1 by NFS
>>
>> And it semes to work well as the mountstatus
>>             LAYOUTGET: 14 14 0 3472 2744 1 1381 1384
>>     GETDEVICEINFO: 1 1 0 196 148 0 5 5
>>      LAYOUTCOMMIT: 8 8 0 2352 1368 0 1256 1257
>>
>> The kernel version I use is 4.18.19.
>>
>> And would anyone please help to clarify following questions ?
>> 1. Can I involve multiple DSs here ?
> 
> Yep, you can add a new iSCSI DS with another filesystem and keep the same
> MD.  The pNFS SCSI layout has support for multi-device layouts, but I don't
> think anyone has put them through the paces.
> 
> The sweet spot for pNFS SCSI is large-scale FC where the fabric allows nodes
> different paths through different controllers.  I expect the do-it-yourself
> with iSCSI target on linux to have a bit more limited performance benefits.
> 
>> 2. Is this stable enough to use in production ? How about earlier version, for example 4.14 ?
> 
> Test it!  It would be great to have more users.
> 
> It would also be great to hear about your workload and if this shows any
> improvements.

Our workload includes large video files or massive small picture files from multiple clients
I will try to setup an environment in real hardware and see what will happen then

> 
> Last note - with SCSI layouts, there's no need to run blkmapd.  The kernel
> should have all the info it needs to find the correct SCSI devices.
> 
> Ben

Regards
Jianchao