David Jonas put forth on 1/14/2011 2:08 PM:
Raid10 is our normal go to, but giving up half the storage in this case seemed unnecessary. I was looking at SAS drives and it was getting pricy. I'll work SATA into my considerations.
That's because you're using the wrong equation for determining your disk storage needs. I posted a new equation on one of the lists a week or two ago. Performance and reliability are far more important now than total space. And today performance means transactional write IOPS not streaming reads. In today's world, specifically for transaction oriented applications (db and mail) smaller faster more expensive disks are less expensive in total ROI that big fat slow drives. The reason is that few if any organizations actually need 28TB (14 2TB Cavier Green drives--popular with idiots today) of mail storage in a single mail store. That's 50 years worth of mail storage for a 50,000 employee company, assuming your employees aren't allowed porn/video attachments, which which most aren't.
Having both SSD and spinning drives in the same SAN controller eliminates the high latency low bandwidth link you were going to use with drbd. It also eliminates buying twice as many SSDs, PCIe RAID cards, and disks, one set for each cluster server. Total cost may end up being similar between the drbd and SAN based solutions, but you have significant advantages with the SAN solution beyond those already mentioned, such as using an inexpensive FC switch and attaching a D2D or tape backup host, installing the cluster filesystem software on it, and directly backing up the IMAP store while the cluster is online and running, or snapshooting it after doing a freeze at the VFS layer.
As long as the SATAboy is reliable I can see it. Probably would be easier to sell to the higher ups too. They won't feel like they're buying everything twice.
Hit their website and look at their customer list and industry awards. They've won them all pretty much. Simple, reliable, inexpensive SAN storage arrays. No advanced features such as inbuilt snapshots and the like. Performance isn't the fastest on the market but it's far more than adequate. The performance per dollar ratio is very high. I've installed and used a SATABlade and SATABoy myself and they're extremely reliable, and plenty fast. Those were spinning models. I've not used SSDs in their chassis yet.
You configure the controller and drives via a web interface over an ethernet port. There's a lot to love in the way Nexsan builds these things. At least, if you're a HardwareFreak like me.
-- Stan