Field notes: OST cache, shared mailboxes and SSD drives
April 23, 2015 1 Comment
As we’ve been running all our staff and students on Office 365 for the best part of a year now we’ve found a few tweaks that may be of interest to a wider audience. Here’s one of them from experiences earlier in the week…
SSD vs HDD
Like many of you out there all our recent machines have been specced with SSD drives as the performance difference is incredible (can you imagine going back to HDD now?!) but the downside being that the size of drive isn’t as large.
This has become less of an issue on newer builds as 120GB drives have dropped right down in price now but for the first-gen machines with 60GB drives we have hit some space issues, mainly due to…
Shared mailbox caching behaviour
In a previous post I’ve mentioned the hybrid cache in Outlook 2013 that makes working with large mailboxes much easier; however what’s hidden away in the small print is that the hybrid cache doesn’t apply to shared mailboxes or other peoples’ mailboxes that you have access to.
That has some knock-on effects that aren’t immediately apparent but have began to manifest themselves recently in a couple of ways:
Low disk space
We’ve had a few calls coming in recently with machines running out of disk space, an issue we’d pretty much consigned to the history books after being spoiled with 160GB+ drives being more than spacious for most generic desktops.
Upon running the old but incredibly useful WinDirStat tool we could see where the space had gone… OST files! The worst case thus far was 35GB in a single file but other machines have had numerous ~7GB files (multiply that by a factor of 3-4 on a machine used by multiple staff and you can soon see where the space goes)
Calendar entries not syncing
Another recent call involved staff responsible for managing other users’ calendars not seeing updates when new entries were added or moved, yet when viewing on another machine or via OWA there was no such problem. What seems to happen is as the OST grows it corrupts and eventually the sync behaviour becomes a bit erratic.
Emails stuck in Outbox
Similar to the calendar scenario above some users have had random emails getting stuck in their Outbox and refusing to send. This particular issue has occurred on smaller OSTs as well as the huge ones above so it seems to be a corruption issue that can pop up from time to time.
The quickest way to fix a corrupted cache is just to delete it. If, however you don’t want to do that for some reason (slow connection, user doesn’t want to wait for cache to reload or has unsynchronised items) you can run the scanpst tool that’s included within Office. It’s not something you’ll find in the Start Menu so run it manually from:
C:\Program Files (x86)\Microsoft Office\Office15\scanpst.exe
In the scenario above where emails were getting stuck in the Outbox scanpst resolved the issue without needing to delete and repopulate the cache so it’s worth a shot as a quick fix
Disable caching for additional mailboxes
Some of our users need to have 10+ additional mailboxes open, others have shared mailboxes with many attachments and have tended to be the ones hit hardest by the caching and disk space issues. If money was no object we could just get them all 250GB+ SSDs but seeing as that’s not the case we need plan b)
The solution is to enable an Office 2013 GPO setting under User Configuration > Administrative Templates:
Outlook 2013 > Outlook Options > Delegates > Disable shared mail folder caching
Once this applies you’ll notice a change in the status bar along the bottom of Outlook, non-cached mailboxes will show up as “Online” (confirmed at the end of the KB article above)
The slight downside is a bit of lag when first opening the folders. For a secondary mailbox that isn’t used as regularly it’s an acceptable compromise, given the issues that users were experiencing with the oversized caches so we’ve rolled it out across the board.
The only thing we’ll have to wait and see is whether the large OSTs reduce in size or if they need deleting to remove the cache that was previously stored for the shared mailboxes.