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You don’t need a Backup solution!

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Well, not exactly.  What you really need is a restore solution!

I was discussing this with a colleague recently as we compared difficulties multiple customers are having with backups in general.  My colleague was relating a discussion he had with his customer where he told them, “stop thinking about how to design a backup solution, and start thinking about how to design a restore solution!”

Most of our customers are in the same boat, they work really hard to make sure that their data is backed up within some window of time, and offsite as soon as possible in order to ensure protection in the event of a catastrophic failure.  What I’ve noticed in my previous positions in IT and more so now as a technical consultant with EMC is that (in my experience) most people don’t really think about how that data is going to get restored when it is needed.  There are a few reasons for this:

  • Backing up data is the prerequisite for a restore; IT professionals need to get backups done, regardless of whether they need to restore the data.  It’s difficult to plan for theoretical needs and restore is still viewed, incorrectly, as theoretical.
  • Backup throughput and duration is easily measured on a daily basis, restores occur much more rarely and are not normally reported on.
  • Traditional backup has been done largely the same way for a long time and most customers follow the same model of nightly backups (weekly full, daily incremental) to disk and/or tape, shipping tape offsite to Iron Mountain or similar.

I think storage vendors, EMC and NetApp particularly, are very good at pointing out the distinction between a backup solution and a restore solution, where backup vendors are not quite as good at this.  So what is the difference?

When designing a backup solution the following factors are commonly considered:

  • Size of Protected Data – How much data do I have to protect with backup (usually GB or TB)
  • Backup Window – How much time do I have each night to complete the backups (in hours)
  • Backup Throughput – How fast can I move the data from it’s normally location to the backup target
  • Applications – What special applications do I have to integrate with (Exchange, Oracle, VMWare)
  • Retention Policy – How long do I have to hang on to the backups for policy or legal purposes
  • Offsite storage – How do I get the data stored at some other location in case of fire or other disaster

If you look at it from a restore prospective, you might think about the following:

  • How long can I afford to be down after a failure?  Recovery Time Objective (RTO): This will determine the required restore speed.  If all backups are stored offsite, the time to recall a tape or copy data across the WAN affects this as well.
  • How much data can I afford to lose if I have to restore? Recovery Point Objective (RPO):  This will determine how often the backup must occur, and in many cases this is less than 24 hours.
  • Where do I need to restore the application? This will help in determining where to send the data offsite.

Answer these questions first and you may find that a traditional backup solution is not going to fulfill your requirements.  You may need to look at other technologies, like Snapshots, Clones, replication, CDP, etc.  If a backup takes 8 hours, the restore of that data will most likely take at least 8 hours, if not closer to 16 hours.  If you are talking about a highly transactional database, hosting customer facing web sites, and processing millions of dollars per hour, 8 hours of downtime for a restore is going to cost you tens or hundreds of millions of dollars in lost revenue.

Two of my customers have database instances hosted on EMC storage, for example, which are in the 20TB size range.  They’ve each architected a backup solution that can get that 20TB database backed up within their backup window.  The problem is, once that backup completes, they still have to offsite the backup, and replicate it to their DR site across a relatively small WAN link.  They both use compressed database dumps for backup because, from the DBA’s perspective, dumps are the easiest type of backup to restore from, and the compression helps get 20TB of data pushed across 1gbe Ethernet connections to the backup server.  One of the customers is actually backing up all of their data to DataDomain deduplication appliances already; the other is planning to deploy DataDomain.  The problem in both cases is that, if you pre-compress the backup data, you break deduplication, and you get no benefit from the DataDomain appliance vs. traditional disk.  Turning off compression in the dump can’t be done because the backup would take longer than the backup window allows.  The answer here is to step back, think about the problem you are trying to solve–restoring data as quickly as possible in the event of failure–and design for that problem.

How might these customers leverage what they already have, while designing a restore solution to meet their needs?

Since they are already using EMC storage, the first step would be to start taking snapshots and/or clones of the database.  These snapshots can be used for multiple purposes…

  • In the event of database corruption, or other host/filesystem/application level problem, the production volume can be reverted to a snapshot in a matter of minutes regardless of the size of the database (better RTO).  Snapshots can be taken many times a day to reduce the amount of data loss incurred in the event of a restore (better RPO).
  • A snapshot copy of the database can be mounted to a backup server directly and backed up directly to tape or backup disk.  This eliminates the requirement to perform database dumps at all as well as any network bottleneck between the database server and backup server.  Since there is no dump process, and no requirement to pre-compress the data, de-duplication (via DataDomain) can be employed most efficiently.  Using a small 10gbps private network between the backup media servers and DataDomain appliances, in conjunction with DD-BOOST, throughput can be 2.5X faster than with CIFS, NFS, or VTL to the same DataDomain appliance.  And with de-duplication being leveraged, retention can be very long since each day’s backup only adds a small amount of new data to the DataDomain.
  • Now that we’ve improved local restore RTO/RPO, eliminated the backup window entirely for the database server, and decreased the amount of disk required for backup retention, we can replicate the backup to another DataDomain appliance at the DR site.  Since we are taking full advantage of de-duplication now, the replication bandwidth required is greatly reduced and we can offsite the backup data in a much shorter period of time.
  • Next, we give the DBAs back the ability to restore databases easily, and at will, by leveraging EMC Replication Manager.  RM manages the snapshot schedules, mounting of snaps to the backup server, and initiation of backup jobs from the snapshot, all in a single GUI that storage admins and DBAs can access simultaneously.

So we leveraged the backup application they already own, the DataDomain appliances they already own, storage arrays they already own, built a small high-bandwidth backup network, and layered some additional functionality, to drastically improve their ability to restore critical data.  The very next time they have a data integrity problem that requires a restore, these customer’s will save literally millions of dollars due to their ability to restore in minutes vs. hours.

If RPO’s of a few hours are not acceptable, then a Continuous Data Protection (CDP) solution could be added to this environment.  EMC RecoverPoint CDP can journal all database activity to be used to restore to any point in time, bringing data loss (RPO) to zero or near-zero, something no amount of snapshots can provide, and keeping restore time (RTO) within minutes (like snapshots).  Further, the journaled copy of the database can be stored on a different storage array providing complete protection for the entire hardware/software stack.  RecoverPoint CDP can be combined with Continuous Remote Replication (CRR) to replicate the journaled data to the DR site and provide near-zero RPO and extremely low RTO in a DR/BC scenario.  Backups could be transitioned to the DR site leveraging the RecoverPoint CRR copies to reduce or eliminate the need to replicate backup data.  EMC Replication Manager manages RecoverPoint jobs in the same easy to use GUI as snapshot and clone jobs.

There are a whole host of options available from EMC (and other storage vendors) to protect AND restore data in ways that traditional backup applications cannot match.  This does not mean that backup software is not also needed, as it usually ends up being a combined solution.

The key to architecting a restore solution is to start thinking about what would happen if you had to restore data, how that impacts the business and the bottom line, and then architect a solution that addresses the business’ need to run uninterrupted, rather than a solution that is focused on getting backups done in some arbitrary daily/nightly window.

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Capacity vs Performance: Thin Provisioning-Reclaiming Free Space

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A comment about HDS’s Zero Page Reclaim on one of my previous posts got me thinking about the effectiveness of thin provisioning in general.  In that previous post, I talked about the trade-offs between increased storage utilization through the use of thin-provisioning and the potential performance problems associated with it.

There are intrinsic benefits that come with the use of thin provisioning.  First, new storage can be provisioned for applications without nearly as much planning.  Next, application owners get what they want, while storage admins can show they are utilizing the storage systems effectively.  Also, rather than managing the growth of data in individual applications, storage admins are able to manage the growth of data across the enterprise as a whole.

Thin provisioning can also provide performance benefits…  For example, consider a set of virtual Windows servers running across several LUNs contained in the same RAID group.  Each Windows VM stores its OS files in the first few GB of their respective VMDK files.  Each VMDK file is stored in order in each LUN, with some free space at the end.  In essence, we have a whole bunch of OS sections separated by gaps of no data.  If all VMs were booting at approximately the same time, the disk heads would have to move continuously across the entire disk, increasing disk latency.

Now take the same disks, configured as a thin pool, and create the same LUNs (as thin LUNs) and the same VMs.  Because thin-provisioning in general only writes data to the physical disks as it’s being written by the application, starting from the beginning of the disk, all of those Windows VMs’ OS files will be placed at the beginning of the disks.  This increased data locality will reduce IO latency across all of the VMs.  The effect is probably minor, but reduced disk latency translates to possibly higher IOPS from the same set of physical disks.  And the only change is the use of thin-provisioning.

So back to HDS Zero Page Reclaim.  The biggest problem with thin provisioning is that it doesn’t stay thin for long.  Windows NTFS, for example, is particularly NOT thin-friendly since it favors previously untouched disk space for new writes rather than overwriting deleted files.  This activity eventually causes a thin-LUN to grow to it’s maximum size over time, even though the actual amount of data stored in the LUN may not change.  And Windows isn’t the only one with the problem.  This means that thin provisioning may make provisioning easier, or possibly improve IO latency, but it might not actually save you any money on disk.  This is where HDS’s Zero Page Reclaim can help.  Hitachi’s Dynamic Provisioning (with ZPR) can scan a LUN for sections where all the bytes are zero and reclaim that space for other thin LUNs.  This is particularly useful for converting thick LUNs into thin LUNs.  But, it can only see blocks of zeros, and so it won’t necessarily see space freed up by deleting files.  Hitachi’s own documentation points out that many file systems are not-thin friendly, and ZPR won’t help with long-term growth of thin LUNs caused by actively writing and then deleting data.

Although there are ways to script the writing of zeros to free space on a server so that ZPI can reclaim that space, you would need to run that script on all of your servers, requiring a unique tool for each operating system in your environment.  The script would also have to run periodically, since the file system will grow again afterward.

NetApp’s SnapDrive tool for Windows can scan an NTFS file system, detect deleted files, then report the associated blocks back to the Filer to be added back to the aggregate for use by other volumes/LUNs.  The Space Reclamation scan can be run as needed, and I believe it can be scheduled; but, it appears to be Windows only.  Again, this will have to be done periodically.

But what if you could solve the problem across most or all of your systems, regardless of operating system, regardless of application, with real-time reclamation?  And what if you could simultaneously solve other problems?  Enter Symantec’s Storage Foundation with Thin-Reclamation API.  Storage Foundation consists of VxFS, VxVM, DMP, and some other tools that together provide dynamic grow/shrink, snapshots, replication, thin-friendly volume usage, and dynamic SAN multipathing across multiple operating systems.  Storage Foundation’s Thin-Reclamation API is to thin-provisioning what OST is to Backup Deduplication.  Storage vendors can now add near-real-time zero page reclaim for customers that are willing to deploy VxFS/VxVM on their servers.  For EMC customers, DMP can replace PowerPath, thereby offsetting the cost.

As far as I know, 3PAR is the first and only storage vendor to write to Symantec’s thin-API, which means they now have the most dynamic, non-disruptive, zero-page-reclaim feature set on the market.  As a storage engineer myself, I have often wondered if VxVM/VxFS could make management of application data storage in our diverse environment easier and more dynamic.  Adding Thin-Reclamation to the mix makes it even more attractive.  I’d like to see more storage vendors follow 3PAR’s lead and write to Symantec’s API.  I’d also like to see Symantec open up both OST and the Thin-Reclamation API for others to use, but I doubt that will happen.

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