rphilippe
Contributor
Contributor

Boot on SAN or local disks ?

Hello,

We are wondering which is better between booting on SAN and booting on a internal RAID 1 array ?

How does VMWare react on a SAN failure or path failure when it's all on SAN ?

VMFS will alway be on the SAN.

Rémi

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16 Replies
MR-T
Immortal
Immortal

Boot from SAN works really well & will handle path failures, but quite honestly it's not as easy to setup.

I tend to go with local installations of ESX and then have VMFS on the SAN.

It's the simple solution which works every time!

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mstahl75
Virtuoso
Virtuoso

We currently boot from SAN. I really couldn't say which is better though. If the SAN is unavailable then even if you are booting locally you won't have access to any of your VMFS volumes anyway so really can't do much.

We have had some SAN issues in the past and on the 3.0.x servers when the SAN came back they were still running. They had a number of errors while the SAN was down but seemed to weather the issue.

Kind of anecdotal but thought I would throw that out there.

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BUGCHK
Commander
Commander

Boot from SAN could be a time-saver if you can use array snapshots (e.g. rollback from corruptions) or data replication in some situations. Very often this can be compensated with an automatic re-installation.

The downside, I think, is that access to logfiles and the contents of the diagnostic partition gets lost when the SAN is down. Especially the logfiles can contain useful troubleshooting information which might not get written if there are errors in the SAN.

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juchestyle
Commander
Commander

rphilippe,

When ever possible keep the setup simple. Only add more complexity (boot from SAN) if there is a feature or need to do so. Go for local boot, that is easy to do.

Respectfully,

Matthew

Kaizen!
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whynotq
Commander
Commander

my personal preference is local disk for the installation and Raid 1 where ever possible.

I have deployed SAN boot in the past but that was for a customer doing array based replication to a DR site, it meant that if the primary went down we could come up on the DR in ~30 minutes with some zoning tweaks and BIOS setup. But then again we can rebuild in ~30 minutes (then of course we have the 1 hour patching experience).

at the end of the day you have a choice and it will depend on your SAN reliability, DR plan, Budget and GUT Feeling...

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depping
Leadership
Leadership

I also deployed boot from SAN a couple of times but i'm definitely no fan. Especially when installing patches I encountered purple screens several times. although the server started normally it's definitely not normal. besides that, local storage seems to be a better option for caching etc.

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TomHowarth
Leadership
Leadership

I'm with Mr-T here, althought Boot form SAN works and handles path failures, I believe in the military paradigm KISS (keep it simple stupid)

Tom Howarth VCP / VCAP / vExpert
VMware Communities User Moderator
Blog: http://www.planetvm.net
Contributing author on VMware vSphere and Virtual Infrastructure Security: Securing ESX and the Virtual Environment
Contributing author on VCP VMware Certified Professional on VSphere 4 Study Guide: Exam VCP-410
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torontoguy
Contributor
Contributor

i;'d boot from SAN for the simple fact of being able to easily move virtual machines from one ESX host to another.

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juchestyle
Commander
Commander

Hey man, you don't have to BOOT from a san to be able to vmotion. You can store your vms on a SAN to accomplish this while still booting from local disks.

Respectfully,

Matthew

Kaizen!
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kreischl
Enthusiast
Enthusiast

I started with boon from SAN on our older IBM HS20 blades and our first SAN but switched to local disk since then on the new servers. Easier setup and the cost of local drives are cheaper. Why waste potential FC bandwidth is my thought.

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grasshopper
Virtuoso
Virtuoso

local disk all the way!

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torontoguy
Contributor
Contributor

ok, you;ll have to excuse me.

"You can store your vms on a SAN to accomplish this while still booting from local disks. "

if your VMDK file that holds your virtual OS is on the SAN, how do you boot from the local drives that reside on your ESX host?

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jesse_gardner
Enthusiast
Enthusiast

This is really simple straightforward best-practice setup of ESX, so I think someone is getting confused here.

The discussion is about where to install ESX (the service console & kernel). General consensus is to install to local SCSI/SAS disks. Then you use fiber channel (etc) to connect to SAN storage and create VMFS volumes on that SAN storage which will hold the VMDK's. Your VM's boot of SAN, in a way, but your host boots off local disks.

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juchestyle
Commander
Commander

Don't over think this torontoguy.

Your ESX is installed locally, and your esx will boot from the local disks. You then connect storage from a SAN to your esx and put your vmdk files for your vms on the SAN storage.

Make sense?

Respectfully,

Matthew

Kaizen!
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msmenne17
Enthusiast
Enthusiast

I think I understand what you're asking here..

ESX Server is installed and booted locally..

Each VM Guest OS is installed and booted from the VMFS (stored on the SAN). So, essentially your VMs are booted from the SAN (they don't know it) while your ESX server is booted locally.

ESX Server is booted, then once that's booted, you start booting VMs inside of the ESX server as processes within the ESX server/vmkernel.

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dpomeroy
Champion
Champion

Besides added complexity we never went with boot from SAN also because our SAN storage is quite expensive.

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