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let's have P2000 G3 with SAS Dual Controller and DL120 G6 with HP SCO3e SAS HBA cards.

1) I know it's bit dumb question, but just to be sure. The array will be filled by SATA disks. Will be the SAS connection to the host degraded to SATA performance ? I hope not ..
2) Does SAS support multipathing ? (XenServer)

Thanks.

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1 Answer 1

Terribly written question, but;

  1. In multi-user environments a single SAS disk is typically quicker than a same size/speed SATA disk due to its superior queue and cache management functions, not by a lot, perhaps onlt 10% but under heavy usage this can be as much as 50% quicker. So on a disk-by-disk basis id could be said that accessing a SATA disk over a SAS link (especially those particular SAS links as they support 4 x 6Gbps channels with those parts) could be slower than going 'fully SAS' yes.
  2. Yes SAS supports dual pathing, but so does SATA in this configuration. Please consider that the particular disk shelf you've bought (I can't honestly call it a SAN as it's not in that configuration) support 8 single pathed hosts or 4 dual pathed ones.

I'm a huge fan of the P2000 range but have never found a use for the SAS version - what are you planning to use it for? I'm just a bit confused/concerned about any cluster functionality you may have in mind.

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So, I have two possibilities, FC/iSCSI single controller with FC HBAs for 2 hosts, or SAS dualcontroller with SAS HBAs for these 2 hosts. As I would like to have dual controllers, and dual FC/iSCSI is out of my budget, I do not have any other option (MSA60 does not have any raid and so on, does it). Do you think it will be working or not ? :/ Or what do you recommend.. (array+2 hosts) –  John Feb 16 '11 at 11:35
    
What is it you're actually trying to build here, as in functionality/operating-systems etc. ? –  Chopper3 Feb 16 '11 at 11:58
    
2xXenServer (linux guests) with HA feature connected to the array. –  John Feb 16 '11 at 12:31
    
So you want two or more hosts to access the same LUN at the same time then right? have you thought about how you're going to do this within the OS? i.e. what file system and locking/cluster manager and do those choices work with SAS? You need to think of these otherwise it will either not work or cause immediate and huge corruption. –  Chopper3 Feb 16 '11 at 14:10
    
Yes, the machines access the same LUN but not at the same time. If one host fails (for ex. management interface goes down) it activates host fencing [it will be restarted so that there will be no VM running - everything done by HA feature of XenServer] , and the VMs are re-run on the second host (designated as a new master of the pool) accessing the same LUN. XenServer sees SAS HBA as FC HBA. –  John Feb 16 '11 at 14:53

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