Kevin OBrien

How To Lower Virtualized Data Center Expense With USB Flash Discussion

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One of the little known or little explored secrets with servers running VMware ESXi 5.x is they can be booted off of USB or SD flash media. In such a scenario, enterprises could dump HBAs or RAID cards and the hard drives or SSDs that are used to boot the servers. Going this route yields a CAPEX benefit for new systems, the cost of flash media for boot is insignificant compared to the drives and storage adapter cards required to spin up a server. There are also gains in OPEX; the implications of moving to USB or SD flash media have a big advantage when considering the power required for a small flash media drive for boot vs. the more common practice of adapters and drives.

How To Lower Virtualized Data Center Expense With USB Flash

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There are another angles in use of Flash media to boot VMware servers.

It is a separation between boot volume and datastores in a smaller enviroments. For example we can configure datastore on disks with RAID card which can be moved to another server if needed. Also when there is some problem with vSphere you can simply overwrite the installation of vSphere without interfering with Datastores.

Yes, you can configure two separate volumes on a RAID card but you lost at least 2 disk slots for such a solutions (RAID1). In a common 8x2,5" server configuration it is a 25% of storage slots lost.

One of most effective scenario of using flash media are also in blade servers that works with any SAN/NAS solution, where you can eradicate expensive media from multiple servers.

We use different flash media to boot VMware since last 3 years in several vSphere hosts and until now there are no a single incindent of flash media failure.

p.s.

From our perspective the most advanced in using of SD/Flash is Dell. They offering dual (mirrored) SD card slots to most of their servers. It can be mounted even after initial purchase so nothing is lost if you missed this on start.

bgs

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p.s.

From our perspective the most advanced in using of SD/Flash is Dell. They offering dual (mirrored) SD card slots to most of their servers. It can be mounted even after initial purchase so nothing is lost if you missed this on start.

bgs

Definitely agree there, would be great to see more major server vendors adopt this as an option.

Nothing wrong with that route, just not what we chose to focus on here.

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I'm curious about the reliability aspect here since the flash drive would be a single point of failure. And with manufacturers seemingly cutting corners everywhere nowadays to have the best prices, flash drives just don't seem that robust to me (although I have yet to have one fail). I'm sure you could replace the flash drive and reload it fairly quickly, I'd rather not have to deal with it.

I'm not familiar with the mirrored flash/SD slots but I'm guessing this is something specifically built into the server. Is there any way to run redundant flash drives if your server doesn't have mirrored flash/SD slots?

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I guess you could break out the USB slot with a splitter but that introduces more points of failure potentially, it just depends on what keeps you up at night ;) I suppose in our example you could also use the internal USB slot and one on the front of the machine too as a physical backup.

Dell offers the dual SD option, most others don't offer this by default though you can add it yourself pretty easily. Here's a PDF on the Dell solution

http://www.dell.com/learn/us/en/04/business~solutions~whitepapers~en/documents~poweredge-idsdm-whitepaper-en.pdf

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Actually my Supermicro servers already have multiple USB slots. My larger question is how to get the server BIOS/VMware to use them in a fashion like RAID 1 so one takes over if the other one fails.

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Even if you could use software raid to get that done, I'm not sure that helps you on reliability. I'd take my chances with a USB drive, which by the way we haven't seen fail nearly at the pace SSDs do. We kill SSDs all the time, $10 USB drive, much less often.

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