09-14-2020, 12:37 PM
Now, when you're actually running those backups, the first thing I keep my eye on is consistency. We're talking about application consistency, mostly. It's not enough to just copy the blocks. You need the application to be in a coherent state, like a database transaction finishing perfectly. Otherwise, when you restore it, it's going to be junk, really broken data, and then you're stuck fixing that later. I always make sure I understand the mechanisms for quiescing the guest OS. It's about telling the system, "Hey, pause what you're doing for a second," so the backup sees a clean picture. But you have to be careful about *how* you quiesce. Too aggressively, and you might break something else inside the VM, or maybe the application itself might complain that you're interfering with its operations. It's a tightrope walk, honestly.
Also, I always think about the snapshotting aspect, too. Snapshots are super useful, sure, but you know they aren't free. They consume resources, especially on a fabric like vSAN where space and overhead are always something to watch. You can take snapshots, and that's part of the process, absolutely. But you gotta manage the lifecycle of those snapshots really tightly. If you forget to clean up old ones, your performance will start to noticeably suffer, and then you're in a really bad spot. You're basically trading short-term convenience for long-term pain, which is a rough deal. I always suggest you have a strict policy for how long those temporary retention points can live.
And performance, man, performance matters so much here. You don't want the backup job itself becoming a bottleneck for your production workload. Because vSAN is inherently performance-sensitive, every extra read or write request from the backup job is stressing the whole system. We have to schedule these things really intelligently. Maybe running big backup operations during peak hours is just asking for trouble. You really want to identify the off-peak times, the quiet spots in the day, when the overall system demand is naturally low. If you can stagger the backups across multiple VMs, that spreads the I/O load, which is much better for the underlying storage infrastructure.
Another concept I keep in mind, which isn't directly part of the backup process itself, but it is critical for the success of the restore, is testing. You have to genuinely, rigorously test your restores. Seriously. Don't just assume the backup software works because the job finished green. You need to pop a VM off the backup media and actually power it on. You need to log into it and check the critical databases, verify the user logins, and run the day's transactions. If you haven't practiced the recovery, the recovery will fail. That's a fact, a hard one.
Plus, you need to think about the immutability of the backups, too. Once you've got the data stored, you really want to make sure nobody can sneak in and accidentally or maliciously change it. This is a massive deal right now, given how much bad actors are out there. You need air-gapped concepts, or at least logically air-gapped storage for your copies. If the attackers compromise your production environment and then they compromise your live backup repository, you've sunk your boat, truly. I always recommend going with something that builds in write-once-read-many protection.
And because we're talking consistency, maybe you should think about application awareness beyond just the OS level. If you've got Oracle running in that VM, or maybe a Microsoft Exchange server, those applications have their own internal coordination needs. The backup tool needs to coordinate with those applications to ensure everything is captured atomically. It's deeper than just pausing the VM; you're asking the application to tell the storage layer, "Hey, everything that is happening right now, please ensure it is consistent up to this point in time." That requires the correct integration mechanisms, and I mean the *right* ones.
I also keep thoughts circling about the network architecture. Because vSAN relies on networking to knit everything together, a bad network segment can absolutely tank your backup job. If your network is struggling with latency or experiencing packet loss, your backup process will either slow to a crawl or it will fail entirely. You should really ensure that the network bandwidth dedicated to the backup traffic is separate and robust, perhaps on a separate VLAN or even a dedicated physical link if your budget allows. You can't let backup traffic compete with production traffic across the same pipes, or you're going to see problems popping up when you need them most.
And hey, maybe you should also think about how the storage itself is provisioned. You need enough space for the backups, obviously, but you also need to factor in the operational overhead that the backup process itself imposes. Think about the indexing that happens, the cataloging of metadata, and the pointers that the backup system maintains. That all takes up space and consumes computational cycles, so you can't just allocate the absolute minimum. I usually try to give a buffer that accounts for growth and overhead, just so we don't run out of room in a panic.
But another thing I always worry about is credential management. Who has access to the backup system? And more importantly, who has access to the *restored* system? You gotta implement a very strict zero-trust model around the backup credentials. You don't want the people managing the backup system to have unrestricted access to the production VMs, and vice versa. Layering those permissions makes the whole setup much tougher to compromise, and that is such a huge part of making sure your recovery plan actually works when the worst happens. You really need those checkpoints, you know. It's complex, but it's worth all the thought, trust me.
