File system alignment still needed?

Question

We are about to do a major expansion on our CX array and in the past we simply created LUNS and assigned them to the host OS. We've had the SAN for nearly 3 years and is used mostly by VMware, Netware and Windows. We are dropping the Netware server, will be removing the Windows servers, expanding VMware and adding Linux Oracle servers.

It was my understanding that the "file alignment" thing was not needed in FLARE19 or above. Is this true? If not, I assume I should go back and "align" all of my LUNS?

We haven't done much detail work on the SAN the past 3 years - mostly left it running as-is so I am starting to learn the specifics of maintaining it.

thanks

Bowling1 · Accepted Answer

CX, DMX, HP, Hitachi, etc. are all the same. It is as Aaron stated an "Intel" issue and not an array or code issue.

The following is a step-by-step guide on how to set up the Disk Offset for ESX 3.x.
http://www.vmware.com/pdf/esx3_partition_align.pdf

ZaphodB · Answer

It may seem a bit self-serving but I believe that current recommendations are to perform the alignment using tools at the OS level. Windows can certainly handle this as can Linux and most of the platforms that I can readily think of.

The chief advantage is that as you manage the storage it is extremely difficult to track and maintain alignment as you snap, expand, move, etc. By using LUNs which are all 0-aligned you avoid the pitfall of having something become unaligned later in its data lifecycle.

Just my $0.02

AranH1 · Answer

File system alignment is required in all iterations of FLARE in Intel based systems. See the "Best Practices for Fibre Channel Storage" document on Powerlink for the full details.

Quick note: You will have to delete and re-create the partitions on existing LUNs to create a properly aligned LUN. So you may not want to undertake the work it involves (backing up and restoring data) unless you are seeing performance problems with the LUNs in question.

Aran

AranH1 · Answer

President Beeblebrox,You are correct and I was not suggesting that the alignment be set using array based tools. In fact the CLARiiON Fibre Channel Storage Best Practices recommends using OS based tools primarily because of the reasons you mentioned.For windows diskpart is the best tool for it ....Aran

fullers1 · Answer

My understanding is that only the Windows OS suffers from this alignment problem. VMWare and NetWare are "immune" and do not need to be aligned. Since you are getting rid of your Windows servers, you shouldn't need to go back and align anything.

If you do need to align the Windows LUNs, you can do it by creating a new LUN and setting an alignment offset of 64 when you create it. Then migrate the existing Windows LUN to the new LUN that has the alignment offset.

It's better to do this at the host level with DISKPART or DISKPAR depending on the version of Windows OS but at this point, you'd have to backup and restore your data. Doing it with the new LUN and migration method will avoid downtime and having to do the backup and restore.

I hope this makes sense.

Bowling1 · Answer

Here is a step-by-step guide on how to set up the Disk Offset for ESX 3.x.http://www.vmware.com/pdf/esx3_partition_align.pdf

AranH1 · Answer

Sean,That is not correct. The disk alignment issue is not related to Windows, it is an issue with intel based platforms. So any system on an intel platform can be affected by this issue. The recommendation is for Linux and VMWare as well as Windows. Read the CLARiiON Fibre Channel Best Practices white paper on Powerlink for more information.Aran

fullers1 · Answer

Thank you for correcting me. I must have misunderstood that the Windows machines on a VMWare host do not need their partitions aligned but the VMWare host itself does.Sorry for the misinformation.

dynamox · Answer

Thanks for the link , i did not know you could align VMFS.

AranH1 · Answer

Yeah, thanks Bowling. That is a good reference to keep handy.

CLARiiON

File system alignment still needed?

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