January 8 2010 Friday

VMware 4.0 and options for TX Logs

As part of my day job (well, one of my many days jobs) I often get drafted in to perform practical magic on Domino servers. One of the first things we do is to move transaction logs to a separate physical drive. This is all fine when your Domino server is stand-alone and you have a plethora hard drive options and bays, but with virtualization it becomes harder to this. When you "plan" your VMware environment most customers will create huge datastores taking up all available disk storage leaving no spare disks in for transaction logs. They then promptly create virtual machines like rabbits having a gang-bang. By the time you realize either:

1) You need to use transaction logging (and it's not just for DAOS, like fiber and exercise it has always been beneficial)
or
2) Your Domino server is running poorly now you have virtualized it

it is too late to change the datastore layouts (either locally or SAN) as all the space has already been allocated. Bummer.
I know, I'll just slip it on the OS drive. That won't hurt anything, right?


Hummm.

One of the worst things you can do to a Domino server is put the transaction logs on a shared drive hurting performance by up to 60%. By shared drive I mean any of the following:
  • On the OS drive
  • On the Domino application drive
  • On the Domino data drive
  • On a drive with any other data on it

All of the above locations can, and usually will, pretty much toast your Domino server performance.

Now, with vSphere 4.0 and the free ESXi 4.0 you are now able to use local SATA connections for storage. That means you can now place your Domino transaction logs on a separate drive (provided you have a bay) on pretty much any server you can run ESX or ESXi on. And you can do this without needing to change those rabbit infested datastores. Even SAN attached Domino servers. How cool is that?

Now, IBM's official recommendation is to put transaction logs to the fastest possible drive (i.e, SAS or SSD drives), and I don't disagree with this, but moving transactions logs to their own, dedicated drive will help considerably even with plain old SATA. If you really want speed as well, you can get 30GB 2.5" SATA Solid State Drives (SSDs) for under $100 now and these drives has amazing seek, write and read speeds. Get a 2.5 to 3.5 SATA conversion cable and you get the best of both worlds. Obviously if you are using archived transaction logging you may want to RAID 1 this, but for circular, a single drive could suffice.

Remember, if you use local drives for transaction logs in VMware and you are using HA or DRS the Domino server will no longer fail over (the TX Logs are static, remember). In these circumstances use Domino clustering for fail over, not v-motion.

Lastly, to avoid a lengthy consistency check when you move logs to a different drive (Domino will re-create them if you are not careful), follow these instructions (for this example I'm assuming you are storing transaction logs on the E: drive):
1.        Stop Domino and stop the service for restarting should a reboot be necessary
2.        Add the new drive to the VMware guest (you can do this while it is running, trust me!)
3.        In Windows Disk Management, assign it as the J: drive and format it
4.        Assign you existing E: a new letter, for example K:
5.        Copy all the tx logs (and any folders) to the newly added J: drive
6.        Go back to disk manager and re-assign J: as E: (you may have to reboot here, so remember where you get to)
7.        Once the new (SSD) E: drive is recognized by Windows, start Domino
8.        Reset the Domino service back to automatic

This is for ESX and ESXi 4.x, not VMware Server.
Darren Duke   |   January 8 2010 03:52:55 PM   |    domino  ssd  storage  vmware    |  
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Comments (2)

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1 - Stuart McIntyre    http://blog.collaborationmatters.com    01/23/2010 3:15:29 AM

Good post Darren.

We've just finished a Domino 8.5 infrastructure refresh using ESX3.5 and Redhat Linux.

Each Domino server was installed on a Redhat image on shared RAIDed disk. However, the Data directories, DAOS and Translog directories were created as separate filesystems on internal SATA RAID-1 pairs (with Data and DAOS co-residing on the same disks). The Domino Mail and/or Apps sub-directories are out on NAS storage.

This gave us the benefits of virtualisation for snapshots, availability etc, but with super fast disk access.

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2 - Turtle    http://www.wabbitcam.com    01/28/2010 2:55:58 PM

Wabbits having a WHAT?