[gpfsug-discuss] Strategies - servers with local SAS disks
Aaron Knister
aaron.s.knister at nasa.gov
Thu Dec 1 04:15:17 GMT 2016
Thanks Zach, I was about to echo similar sentiments and you saved me a
ton of typing :)
Bob, I know this doesn't help you today since I'm pretty sure its not
yet available, but if one scours the interwebs they can find mention of
something called Mestor.
There's very very limited information here:
-
https://indico.cern.ch/event/531810/contributions/2306222/attachments/1357265/2053960/Spectrum_Scale-HEPIX_V1a.pdf
-
https://www.yumpu.com/en/document/view/5544551/ibm-system-x-gpfs-storage-server-stfc
(slide 20)
Sounds like if it were available it would fit this use case very well.
I also had preliminary success with using sheepdog
(https://sheepdog.github.io/sheepdog/) as a backing store for GPFS in a
similar situation. It's perhaps at a very high conceptually level
similar to Mestor. You erasure code your data across the nodes w/ the
SAS disks and then present those block devices to your NSD servers. I
proved it could work but never tried to to much with it because the
requirements changed.
My money would be on your first option-- creating local RAIDs and then
replicating to give you availability in the event a node goes offline.
-Aaron
On 11/30/16 10:59 PM, Zachary Giles wrote:
> Just remember that replication protects against data availability, not
> integrity. GPFS still requires the underlying block device to return
> good data.
>
> If you're using it on plain disks (SAS or SSD), and the drive returns
> corrupt data, GPFS won't know any better and just deliver it to the
> client. Further, if you do a partial read followed by a write, both
> replicas could be destroyed. There's also no efficient way to force use
> of a second replica if you realize the first is bad, short of taking the
> first entirely offline. In that case while migrating data, there's no
> good way to prevent read-rewrite of other corrupt data on your drive
> that has the "good copy" while restriping off a faulty drive.
>
> Ideally RAID would have a goal of only returning data that passed the
> RAID algorithm, so shouldn't be corrupt, or made good by recreating from
> parity. However, as we all know RAID controllers are definitely prone to
> failures as well for many reasons, but at least a drive can go bad in
> various ways (bad sectors, slow, just dead, poor SSD cell wear, etc)
> without (hopefully) silent corruption..
>
> Just something to think about while considering replication ..
>
>
>
> On Wed, Nov 30, 2016 at 11:28 AM, Uwe Falke <UWEFALKE at de.ibm.com
> <mailto:UWEFALKE at de.ibm.com>> wrote:
>
> I have once set up a small system with just a few SSDs in two NSD
> servers,
> providin a scratch file system in a computing cluster.
> No RAID, two replica.
> works, as long the admins do not do silly things (like rebooting servers
> in sequence without checking for disks being up in between).
> Going for RAIDs without GPFS replication protects you against single
> disk
> failures, but you're lost if just one of your NSD servers goes off.
>
> FPO makes sense only sense IMHO if your NSD servers are also processing
> the data (and then you need to control that somehow).
>
> Other ideas? what else can you do with GPFS and local disks than
> what you
> considered? I suppose nothing reasonable ...
>
>
> Mit freundlichen Grüßen / Kind regards
>
>
> Dr. Uwe Falke
>
> IT Specialist
> High Performance Computing Services / Integrated Technology Services /
> Data Center Services
> -------------------------------------------------------------------------------------------------------------------------------------------
> IBM Deutschland
> Rathausstr. 7
> 09111 Chemnitz
> Phone: +49 371 6978 2165 <tel:%2B49%20371%206978%202165>
> Mobile: +49 175 575 2877 <tel:%2B49%20175%20575%202877>
> E-Mail: uwefalke at de.ibm.com <mailto:uwefalke at de.ibm.com>
> -------------------------------------------------------------------------------------------------------------------------------------------
> IBM Deutschland Business & Technology Services GmbH / Geschäftsführung:
> Frank Hammer, Thorsten Moehring
> Sitz der Gesellschaft: Ehningen / Registergericht: Amtsgericht
> Stuttgart,
> HRB 17122
>
>
>
>
> From: "Oesterlin, Robert" <Robert.Oesterlin at nuance.com
> <mailto:Robert.Oesterlin at nuance.com>>
> To: gpfsug main discussion list
> <gpfsug-discuss at spectrumscale.org
> <mailto:gpfsug-discuss at spectrumscale.org>>
> Date: 11/30/2016 03:34 PM
> Subject: [gpfsug-discuss] Strategies - servers with local SAS
> disks
> Sent by: gpfsug-discuss-bounces at spectrumscale.org
> <mailto:gpfsug-discuss-bounces at spectrumscale.org>
>
>
>
> Looking for feedback/strategies in setting up several GPFS servers with
> local SAS. They would all be part of the same file system. The
> systems are
> all similar in configuration - 70 4TB drives.
>
> Options I?m considering:
>
> - Create RAID arrays of the disks on each server (worried about the RAID
> rebuild time when a drive fails with 4, 6, 8TB drives)
> - No RAID with 2 replicas, single drive per NSD. When a drive fails,
> recreate the NSD ? but then I need to fix up the data replication via
> restripe
> - FPO ? with multiple failure groups - letting the system manage
> replica
> placement and then have GPFS due the restripe on disk failure
> automatically
>
> Comments or other ideas welcome.
>
> Bob Oesterlin
> Sr Principal Storage Engineer, Nuance
> 507-269-0413 <tel:507-269-0413>
>
> _______________________________________________
> gpfsug-discuss mailing list
> gpfsug-discuss at spectrumscale.org <http://spectrumscale.org>
> http://gpfsug.org/mailman/listinfo/gpfsug-discuss
> <http://gpfsug.org/mailman/listinfo/gpfsug-discuss>
>
>
>
>
> _______________________________________________
> gpfsug-discuss mailing list
> gpfsug-discuss at spectrumscale.org <http://spectrumscale.org>
> http://gpfsug.org/mailman/listinfo/gpfsug-discuss
> <http://gpfsug.org/mailman/listinfo/gpfsug-discuss>
>
>
>
>
> --
> Zach Giles
> zgiles at gmail.com <mailto:zgiles at gmail.com>
>
>
> _______________________________________________
> gpfsug-discuss mailing list
> gpfsug-discuss at spectrumscale.org
> http://gpfsug.org/mailman/listinfo/gpfsug-discuss
>
--
Aaron Knister
NASA Center for Climate Simulation (Code 606.2)
Goddard Space Flight Center
(301) 286-2776
More information about the gpfsug-discuss
mailing list