Re: XFS on RBD on EC painfully slow

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I had it on my list of things to possibly try, a tar in | tar out copy to see if it yielded different results.

On its face, it seems like cp -a is getting ever so slightly better speed, but not a clear night and day difference.

I will definitely look into this and report back any findings, positive or negative.

Thanks for the suggestion,

Reed

> On May 28, 2021, at 3:24 AM, Matthias Ferdinand <mf+ml.ceph@xxxxxxxxx> wrote:
> 
> On Thu, May 27, 2021 at 02:54:00PM -0500, Reed Dier wrote:
>> Hoping someone may be able to help point out where my bottleneck(s) may be.
>> 
>> I have an 80TB kRBD image on an EC8:2 pool, with an XFS filesystem on top of that.
>> This was not an ideal scenario, rather it was a rescue mission to dump a large, aging raid array before it was too late, so I'm working with the hand I was dealt.
>> 
>> To further conflate the issues, the main directory structure consists of lots and lots of small file sizes, and deep directories.
>> 
>> My goal is to try and rsync (or otherwise) data from the RBD to cephfs, but its just unbearably slow and will take ~150 days to transfer ~35TB, which is far from ideal.
> 
> (Disclaimer: no experience with cephfs)
> 
> I found rsync a wonderful tool for long distances and large files, less
> so for local networks and small files, even with local disks.
> 
> Usually I do something like
> 
> ( cd src/ && tar --acls --xattrs --numeric-owner --sparse -cf - . ) | 
>  pv -pterab |
>  (cd dst/ && tar --acls --xattrs --numeric-owner --sparse -xf -)
> 
> If src and dst are not mounted on the same machine you can use
> netcat/socat to stream the tar from one system to the other, or pipe it
> through ssh if you need encrypted transport.
> 
> This does not have the resume capability of rsync, but for small files
> it is much faster. After that you can still throw in a final rsync for
> changes accumulated while the initial transfer was running.
> 
> Matthias
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