[TriLUG] SAN file locking

Matt Pusateri mpusateri at wickedtrails.com
Mon Dec 19 20:53:06 EST 2011


Oracle still sells the Sunstore devices.  One nice thing about them, is their built on ZFS, so you get replication and dedupe for free, as opposed to giving EMC/NetApp licensing fees for the same features.  The help system in them is a Mediawiki install, so you can edit the wiki pages to augment the on device documentation with your own companies notes and procedures.


Matt P.

On Dec 19, 2011, at 10:12 AM, Jim Ray wrote:

> It is my understanding the some of the SANs available have the ability
> to combine things like fast and expensive SSD with slow and cheap SATA
> (well, not so cheap after Thailand flood).
> 
> Any recommendation on a starter SAN in the 9 TB+ range? I am interested
> in EMC, netapp and HP/LeftHand yet am open to suggestion.
> 
> Regards,
> 
> Jim Ray, President
> 
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> -----Original Message-----
> From: trilug-bounces at trilug.org [mailto:trilug-bounces at trilug.org] On
> Behalf Of bak
> Sent: Monday, December 19, 2011 9:52 AM
> To: Triangle Linux Users Group General Discussion
> Subject: Re: [TriLUG] SAN file locking
> 
> On 12/18/11 7:35 PM, Joseph Mack NA3T wrote:
>> Thanks everyone
> 
> Anytime Joe; this is a topic I actually know something about, so glad to
> share. :)
> 
>> sorry that went over my head. With a SAN you have blocks, but you're 
>> going to have to partition them and put a FS on them before you use 
>> them. After that the only difference I see is whether the disks are 
>> connected internally or over FC or ethernet. What am I missing?
> 
> Let me put it another way.
> 
> With NAS, the NAS controller owns the blocks and the filesystem and has
> an /etc/exports file.
> 
> With SAN, the SAN controller owns the blocks, but not the filesystem.
> The individual servers connecting to the SAN handle that.
> 
> Some operating systems are OK with having a read-only filesystem
> attached. But solutions like this for the SAN space are not there,
> because the problem to be solved would have to be
> 
> -- Useful even with a read-only filesystem
> -- Requiring the sort of low-latency performance SAN provides
> -- Not more cheaply and easily deployed with a r/o NFS export
> 
> So your discussion with Greg below is interesting from a theoretical
> point of view but I am not aware of any SAN deployments in the real
> world that look like this.
> 
> By the way, SAN is not only FC -- iSCSI and Fibre Channel over Ethernet
> also are considered SAN protocols, since like FC they are basically
> encapsulated SCSI commands.
> 
>> I don't know where redundancy is. I would have expected it at the 
>> block level and the blocks that the SAN hands you are already RAID'ed 
>> before you get them.
> 
> Usually you can specify what sort of RAID levels you'd like (5, 6, 1,
> 0+1 are common). The idea is that any disk problems or failures will be
> invisible to the server.
> 
> Disk arrays that don't do this are known as JBOD (just a bunch of disks)
> and it is up to the host's HBA (SCSI host bus adapter) to handle RAID.
> 
>>> What happens when you have a gaming rig?
>> 
>> I'm assuming a gaming rig is only at home and you won't be having a 
>> SAN at home (too expensive and not enough machines to share the cost 
>> of the SAN).
> 
> Yes.
> 
>> I saw perhaps 10cabs of 42U of disks the other day, all FC SAN. 
>> There's got to be more than boot disks and Oracle databases on there 
>> for the 160 machines I was checking.
> 
> MS Exchange, business analytics, big databases, VMWare guests. It's
> common for SAN environments to have a tiny boot drive and everything
> else lives on shared SAN storage. Especially VMWare. Those 10 cabinets
> of disks plus another cabinet or two of beefy x86 servers with gobs of
> RAM might have been 30 cabinets of stand-alone servers, each with their
> barely-utilized 3-5 disks. Now they have one or two disks, or they boot
> from the SAN.
> 
> Also with SANs, density varies hugely for performance reasons. Every
> disk in a SAN has a maximum number of operations per second it can
> handle. I'm really simplifying here, but all other things being equal,
> 28 drives that are 500GB each are going to be faster than 14 drives that
> are 1TB each. More spinning disks means more disks to satisfy read/write
> requests.
> 
> Of course the SAN controller is doing some coordinating behind the
> scenes to make reads and writes across all those disks as efficient as
> possible, and there's certainly a point of diminishing returns, but
> plenty of folks are happy with more disks and less storage for
> performance reasons.
> 
> Of course the introduction of SSD technology is changing the way all
> this works quite quickly.
> 
> I agree with everything Aaron said. :)
> 
> --bak
> --
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