My adventures using rack mount ReadyNAS with an external drive array.
I have been experimenting with using an external SAS chassis with a rack-mount ReadyNAS. My test beds are an RN4200V2 and RD5200 running OS6 and a Netapp DS4243 24-bay chassis with SAS and SATA drives (actual spinning drives, not SSDs). I used a PCI LSI 9200-8E SAS HBA on the RN4200V2 and the built-in SAS expansion ports of the RD5200. For those not aware, the RN4200V2 and RD5200 motherboards are basically the same (OEMed SuperMicro X8SI6), but the RD5200 uses a SAS2 expansion backplane, which allows it to also have external SAS ports without a second controller, where the RN4200V2 uses a dumb backplane, so can only host 8 drives total on SAS (the other 4 being driven by SATA ports). How this and the end results of my tests would differ on a newer rack-mount native OS6 systems, I cannot say.
The results are mixed, and not something useful for any but the stout-hearted with at least some basic Linux skills. But, here they are.
SAS vs. SATA makes no difference, except that SAS drives lack most of the SMART capabilities of SATA. But since fewer can use them, I bought a batch of used SAS for half the price of SATA. They can be mixed with no problems (though I did not mix in a single volume). It might make a difference if I was using a chassis capable of >3Gb/sec transfer (the NetApp isn't), but I rather doubt it. Turning on the motherboard SAS BIOS extension made no difference except to slow down the boot while it initializes. This is definitely far faster than an EDA500 on an RN516 eSATA port.
It works better with the RD5200 than the RN4200V2. Neither shows more than the 12 internal drives and bays on the Volumes or Performance pages. With the RN4200V2, the PCI HBA apparently gets seen before the onboard SAS or SATA controllers, so the GUI confuses what drives are internal and external. At one point, I saw external drive one as internal drive one and two drive fives. Just putting in the HBA "reserves" internal drive 1, with the drive in actual slot 1 showing up as drive 2, etc. With the RD5200, all the drives are in the right places when seen with SSH, but the GUI shows none of them as drives. Both do recognize when a drive is inserted or removed (alert and log entry), with the RD5200 properly indicating the position (external chassis, drive X). Interestingly, RAIDar 6.5 picks them all up.
From SSH, I can create volumes and shares, and those do get seen by the NAS. I can also export and import volumes on drives in the chassis. But that's a lot of work that would be a lot easier via the GUI.
Since the RD5200 was designed to work with the EDA4000 (though under ReadyData OS, not ReadyNAS OS), which is another 24-drive chassis, maybe none of this is too surprising. Maybe not so surprising, either, that the drives don't show in the GUI. Unlike an eSATA chassis (where the NAS can't tell an EDA500 from a generic chassis), SAS expanders can identify themselves. And I suppose Netgear wants to sell folks an EDA4000 rather than let them use slightly outdated NetApp chasses that can be picked up for 1/10 the price. Then again, the EDA4000 may not show up either under ReadyNAS OS6 on these machines not intended to run that OS.
If anyone has any ideas on how to get the drives in the external chassis to show up in the GUI, preferably as an EDA4000, or make the drives in the chassis take their rightful places when attached by an HBA, even if still not shown in the GUI, give me a shout. I plan to experiment for a while longer.
It would be interesting to see if an HBA could be shoehorned into a desktop NAS with a PCI slot for the 10GB NIC and see how that works.
