BACKUP/MASTER:Immediate Relief with Disk Backup

Presented byW. Curtis Preston

VP, Service DevelopmentGlassHouse Technologies, Inc

Tape backups are taking too longHigh-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 offsite tapes

Many people aren’t utilizing the tape drives properly and are

not getting all their backups done

Also, many are not creating offsite 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 challengesTapes 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

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 offsite copiesAssuming 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 offsite 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

Connect array to clients or backup

servers via Fibre Channel & SANs, or GbE

& NFS/CIFS

BackupClient

BackupServer

ATA DiskArray

Tape

Copy or secondbackup

NFS/CIFS/SAN

What to do with them? (2)Back up to disk first using your backup

software of choiceDuplicate disk backups to tapeExcept in disaster, restores come from diskMaybe place (another?) disk unit offsite

and replicate to it

BackupClient

BackupServer

ATA DiskArray

Tape

Copy or secondbackup

NFS/CIFS/SAN

ATA DiskArray

Offsite

ATA DiskArray

Offsite

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 back up 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 up that

array using backup

software, and

duplicate to tape for

offsite copies

Allows you to use

replication without

the cost of traditional

RAID arrays

BackupClient

BackupClient

BackupClient

ATA Array

ReplicationServer

Tape

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 ¼ the price!

Back up 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 back up 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” onsite or offsite

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

Creation of a “Synthetic Full” would be very nice

Backup twinning should be able to go to disk and tape

In ShortDoing 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

A directory of ATA Fibre & SCSI addressable arrays is available at:

http://www.storagemountain.com

Questions to cpreston@glasshouse.com