Here's what the hosting company posted about it, verbatim. All times quoted are Pacific Standard Time, which is UTC - 8 hours.
The Outage seems to have begun at about 22:56 on 2013-01-15 UTC and ended at around 02:00 on 2013-01-17 UTC.Hello,
Update - 10:00 PM -- Data migration is still completing. We hope to be able to call this finished very soon!
Update - 6:54 PM -- Data migration to the new hardware is nearly complete. Most customers should be seeing their sites loading, but a few may still not be seeing their content yet. I am very sorry for the delay, and thank you for your continued patience!
Update - 12:45pm PST -- The replacement hardware had some bad disks which needed to be replaced. Now that the drives are all in good health, we are rebuilding the RAID array to finalize the preparation of the server. Once that is complete, we will be able to migrate data back to the new server and bring everything back online. Thanks for your patience!
Update - 10:00am PST -- The replacement server is almost done being set up and once it is ready we will be migrating everything to the new hardware. This process is taking longer than expected, but should be underway shortly. Please check back here for more updates!
Update! We are still in the process of replacing this hardware and getting everything back online. We are actively moving data and taking a different approach so that we can get this server back online as quickly as possible. Please check back here for more updates throughout the morning!
As a reminder...
You are receiving this message because your web hosting services are being affected by hardware maintenance due to issues with your shared MySQL server perch.
Due to issues with the RAID controller, we are replacing the hardware for this server and will be restoring all data from our backup server to the new hardware. Unfortunately, this will cause your databases to be offline until they are restored. We sincerely apologize for the inconvenience and will work to bring them back online as quickly as possible.
Once the 'all clear' is given by us, if you're still having trouble loading your sites or access your server, please let us know the specifics, so we can take a look for you. You may contact us either by replying to this message from your inbox, or by submitting a support ticket in the DreamHost panel (https://panel.dreamhost.com/), under Support/Contact Support.
This notice will also appear on that page in your DreamHost Panel and will be updated throughout the process with the latest details we can provide.
This incident is only related to the shared MySQL server perch, and no other servers or services (such as web or email) are affected.
Thank you for your patience!
The Happy DreamHost Server Fixing Team
Being a computing professional, and having worked on hardware in a field-engineering gig, I feel for the guys in the trenches and machine-rooms; it's no fun when you're dealing with a dead system and likely have everybody from your immediate boss to most of the way up the food chain harassing you for current status (and, no, they do not like the very accurate answer of, "It'll be done when it's done.). So this one, at around 24 hours must've been excruciating.