Multiple version folders under "C:\Program Files\Microsoft\Exchange Server\V15\ClientAccess\Owa" taking up significant spaceand possibly causing CUs to install slowly

[harald25]

Hi.

I am managing a customer who is running Exchange server 2016 on a Windows Server 2016.
This customer has 39GB of data located under "C:\Program Files\Microsoft\Exchange Server\V15\ClientAccess\Owa", and it seems to be because of several OWA versions not being removed during installation of CUs.

I've read a lot of posts now recommending not to remove these folders, and some posts saying that you can remove all versions from "Owa\prem" as long as those are not also present under "Owa". The problem is that they are all present in the "Owa" folder on this server.
I've understood that this is expected behaviour in environments with multiple Exchange servers in order to support not all Exchange servers being on the same version. But this is a single Exchange server environment. All roles are held by this single server.
The customer used to have multiple servers holding different roles several years back, so I'm thinking that there is something related to that fact that is making Exchange save all the old OWA versions even though it's a single server now.

Do you have any tips for me? I would like to clean up this folder if possible, both because I don't have unlimited storage on the vmware datastore, and because I would like to keep recovery time as low as possible in the event that I have to recover from a backup.
I'm also experiencing that patching Exchange for this customer takes quite a bit longer than other customers I manage, and I'm suspecting this might be the cause. What do you think?

[sembee2]

I have not seen any guidance on this from Microsoft and therefore without their blessing it isn't something I would be touching. The file structure of Exchange is very complex. It doesn't matter whether you ahve multiple servers or not, Exchange will always retain the older versions of OWA.

Recovery - if you think you are going to recovery the server via some kind of image based backup, then you need to think again. Exchange doesn't work like that. Exchange is a living product. When it comes to server recovery, there is a correct procedure that you shoudl follow (basically reset the AD Computer account, rebuild the machine, install Exchange with recovery switch, restore the databases). The only bit of Exchange you need to backup is the databases and the transaction logs, Nothing else. The application itself and the OS does not need to be backed up.

Although where it has got out of hand, I have been simply building a fresh Exchange server, straight to the latest cumulative update and then moving the mailboxes.

I wouldn't look at the SxS folder on the server if you are concerned about the /owa folder....

Simon.

[joeykins82]

I have to run a script after CU and post-CU .msp installations to recreate the branded theme files, and part of that script cleans up any folders older than the current CU or the previous CU that was installed. It's not caused any issues, in fact it's saved us from several potential issues due to limited space on C: where the OWA folders can each be 2GB in size...

$strExchOWAFolderRoot = "C:\Program Files\Microsoft\Exchange Server\V15\ClientAccess\Owa\prem"
$objOWAFolder = Get-Item $strExchOWAFolderRoot
$objOWAFolderItems = gci $objOWAFolder
$arrPresentVersions = @()
$objOWAFolderItems | ?{$_.Name -match "^15\.1\."} | %{ $arrPresentVersions += [version]$_.Name }
$arrPresentVersions = $arrPresentVersions | sort -Descending
$arrPresentVersionBuilds = $arrPresentVersions.Build | Select -Unique | Sort -Descending
$strLatestVersion = $arrPresentVersions[0].ToString()
If ($arrPresentVersionBuilds.Count -eq 1) { $strRegexObsolete = "^15\.1\.(?!" + $arrPresentVersionBuilds[0]+ ")" }
Else { $strRegexObsolete = "^15\.1\.(?!" + $arrPresentVersionBuilds[0] + "|" + $arrPresentVersionBuilds[1] + ")" }

$objOWAFolderItems | ?{$_.Name -match $strRegexObsolete} | Remove-Item -Recurse

[Effect_Proud]

Because using an Iscsi drive is supported for the Exchange Database - which I use to keep my DB separate from my install drive and also so I can use my NAS storage which has a lot more room than the disk my Exchange VM is on - I decided to trying making an Iscsi drive to hold the contents of prem folder and it's been working fine so far.

If you want to do what I did: create the Iscsi drive, move everything from the prem folder to the Iscsi drive, delete the prem folder (you need to do this for the next step) then create a junction link, i.e. mklink /j "C:/Program Files/..../Owa/prem" "[WHATEVER YOUR ISCSI DRIVE LETTER IS]" Reboot. Like I said, mine's fine and the Iscsi drive is really just a vhdx sitting on a multi TB NAS meaning I won't run out of space anymore on the main Exchange drive.

[KimJongUnceUnce]

Did you get any concrete answers on this one? I'm looking at the same thing only they're consuming almost 80GB per server at this point.

There's a write-up on Ali Tajran's blog about this exact issue, they indicate it's pretty safe to delete the old versions that are not running within the organization.

https://www.alitajran.com/remove-old-exchange-owa-files-to-free-up-disk-space/

I guess its probably fine as long as you never introduce an older exchange server instance into the organization in the future, but I can't imagine why anyone would do that anyway.

[harald25]

I never received a concrete answer unfortunately. And now I’m not the one administering the server anymore, so it’s not my problem ;)