BACKUP/MASTER: Immediate Relief with Disk Backup Presented by W. Curtis Preston VP, Service Development Glass. House Technologies, Inc
Tape backups are taking too long l High-speed tape drives in a library are the standard, but the cost of these units causes many people to cut corners elsewhere l The nature of tape drives also creates difficulty when creating offsite tapes l Many people aren’t utilizing the tape drives properly and are not getting all their backups done l Also, many are not creating offsite copies l Stand-alone tape drives must be swapped
Tape drives: The advantages l High-speed, low cost l Good archival solution. Allows multiple copies without significant cost. l Lots of new tape drives on the market: • • 9940 B (30/70 MB/s) AIT-3 (15/30 MB/s) LTO (15/30 MB/s) Super DLT (11/22 MB/s)
Tape: The challenges l 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 more l Tape-to-tape copying takes time, and multiplexing increases that time – especially if you de-multiplex l Must perform regular full backups to reduce number of tapes required for restore l Incremental backups do not supply enough data to stream a tape drive
Tape: The challenges (2) l Cannot write to single tape drive from two shared servers simultaneously l Single tape can cause large restore to fail l You never know if a tape is good until you really need it
Still not making offsite copies l Assuming copy is same speed as backup, must buy at least twice as many drives to perform copies in one day l If copy is not same speed, must accept longer copy window or buy more tape drives l Additional drives cost a lot of money l Result: Many people still not making offsite copies
Solution: New backup media l Really inexpensive disk arrays • • IDE/ATA-based • 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! Addressable via Fibre Channel, SCSI, Firewire, NFS, or CIFS
What to do with them? l Buy enough disk for two full backups and many, many incremental backups l Connect array to clients or backup servers via Fibre Channel & SANs, or Gb. E & NFS/CIFS
What to do with them? (2) l Back up to disk first using your backup software of choice l Duplicate disk backups to tape l Except in disaster, restores come from disk l Maybe place (another? ) disk unit offsite and replicate to it
What to do with them? (3) l 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 l New products designed to back up to disk • • Forever incremental w/o performance hit Some even eliminate redundant blocks across hosts
What to do with them? (4) l Replicate many clients to a central array, back up that array using backup software, and duplicate to tape for offsite copies l Allows you to use replication without the cost of traditional RAID arrays
What to do with them? (5) l Could also use software-based RAID to create additional mirror, and split mirror for backups l Gives you BCV functionality for ¼ the price! l Back up large databases with no I/O overhead on server!
Why would you do that? l Don’t require constant stream l No need to multiplex on most disk devices l Depending on implementation, multiplexed backups may still be faster on disk l If you did multiplex your disk backups, you could easily de-multiplex the tape copies with no performance penalty l NFS/CIFS devices can be used simultaneously by many clients, without needing to stream each device
Why would you do that? (2) l Incremental backups with little data will not hurt performance of other backups l Protected via monitored RAID -- the loss of a single disk would be monitored and repaired, while the RAID group continued to protect the data l Disk-to-tape copies are easier than tape-totape copies l Could perform infrequent full backups without increasing the chance of failure l Full backups can be performed less often, saving networks and CPU utilization
Why not back up everything to disk? l Archiving purpose of backups requires older backups to be available l Tapes still much cheaper, allowing for multiple, stable copies to be put on “the shelf” onsite or offsite l Tapes not susceptible to filesystem corruption
Issues… l 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 (policybased, not just retention-based. ) l Increase of recovery • Need to be able to import disk images l Creation of a “Synthetic Full” would be very nice l Backup twinning should be able to go to disk and tape
In Short l Doing backups to inexpensive disk first allows for: • • Faster, easier backups – especially incremental backups Easier creation of offsite tapes Easier restores both on- and offsite Many other features l A directory of ATA Fibre & SCSI addressable arrays is available at: http: //www. storagemountain. com l Questions to cpreston@glasshouse. com
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