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Integrating Disk into Backup for Faster Restores. Presented by W. Curtis Preston President The Storage Group, Inc. Tape backups are taking too long. High speed tape drives in a library are the standard, but the cost of these units causes many people to cut corners elsewhere
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Integrating Disk into Backup for Faster Restores Presented by W. Curtis Preston President The Storage Group, Inc.
Tape backups are taking too long • High speed tape drives in a library are the standard, but the cost of these units causes many people to cut corners elsewhere • The nature of tape drives also creates difficulty when creating off-site tapes • Many people aren’t utilizing the tape drives properly, and are not getting all their backups done • Also, many are not creating off-site copies • Stand-alone tape drives must be swapped
Tape drives – the advantages • High speed, low cost • Good archival solution. Allows multiple copies without significant cost. • Lots of new tape drives on the market • 9940B (30/70 MB/s) • AIT-3 (15/30 MB/s) • LTO (15/30 MB/s) • Super DLT (11/22 MB/s)
Tape - the challenges • Tapes are now too fast! • Must use multiplexing to stream them during network backups • Must use higher multiplexing values than ever before, hurting restore performance even more • Tape to tape copying takes time, and multiplexing increases that time – especially if you de-multiplex • Must perform regular full backups to reduce number of tapes required for restore • Incremental backups do not supply enough data to stream a tape drive.
Tape - the challenges (2) • Cannot write to single tape drive from two shared servers simultaneously • Single tape can cause large restore to fail • You never know if a tape is good until you really need it
Still not making off-site copies • Assuming copy is same speed as backup, must buy at least twice as many drives to perform copies in one day • If copy is not same speed, must accept longer copy window or buy more tape drives • Additional drives cost a lot of money • Result: Many people still not making off-site copies
Solution: New backup media • Really inexpensive disk arrays • IDE/ATA based • Addressable via Fibre Channel, SCSI, Firewire, NFS, or CIFS • JBOD and RAID configurations (Use their RAID controller or a software volume manager.) • As low as $5,000 per TB for off-shelf units, $2,000 for build-your-own units!
What to do with them? • Buy enough disk for two full backups and many, many incremental backups (Can roll full backups) • Connect array to clients or backup servers via Fibre Channel & SANs, or GbE & NFS/CIFS
What to do with them? (2) • Back up to disk first using your backup software of choice • Duplicate disk backups to tape, send off-site • Except in disaster, restores come from disk • Maybe place (another?) disk unit off-site and replicate to it
What to do with them (3) • Most backup products do things that are not necessary when backing up to disk • Occasional full backups • Backing up redundant files • Incremental backups of entire files • New products designed to backup to disk • Forever incremental w/o performance hit • Some even eliminate redundant blocks across hosts
What to do with them? (4) • Replicate many clients to a central array, back that array up using backup software, and duplicate to tape for off-site copies • Allows you to use replication without the cost of traditional RAID arrays
What to do with them (5) • Could also use software-based RAID to create additional mirror, and split mirror for backups • Gives you BCV functionality for a fraction of the price! • Backup large databases with no I/O overhead on server!
Why would you do that? • Don’t require constant stream • No need to multiplex on most disk devices • Depending on implementation, multiplexed backups may still be faster on disk • If you did multiplex your disk backups, you could easily de-multiplex the tape copies with no performance penalty • NFS/CIFS devices can be used simultaneously by many clients, without needing to stream each device
Why would you do that? (2) • Incremental backups with little data will not hurt performance of other backups • Protected via monitored RAID -- the loss of a single disk would be monitored and repaired, while the RAID group continued to protect the data • Disk to tape copies are easier than tape to tape copies • Could perform infrequent full backups without increasing the chance of failure • Full backups can be performed less often, saving networks and CPU utilization
Why not do everything to disk? • Archiving purpose of backups requires older backups to be available • Tapes still much cheaper, allowing for multiple, stable copies to be put on “the shelf” on-site or off-site • Tapes not susceptible to filesystem corruption
Issues… • Staging process needs automation • Need to automatically move data from disk to tape without removing from disk • Should allow you to leave backups on disk ALAP, and automate moving data to tape when necessary (policy based, not just retention based.) • Increase ease of recovery • Need to be able to import disk images • More products should support the creation of a “Synthetic Full,” creating a full from many incrementals • Backup twinning should be able to go to disk and tape
In Short • Doing backups to inexpensive disk first allows for • Faster, easier backups – especially incremental backups • Easier creation of offsite tapes • Easier restores both on- and off-site • Many other features • A directory of ATA Fibre & SCSI addressable arrays is available at: http://www.storagemountain.com • Questions to curtis@thestoragegroup.com
Thank you! W. Curtis Preston President The Storage Group, Inc.