In this chapter
we'll discuss hardware that we would need in order to run our backup
system. The backup system temporally stores data from servers to
backup's server storage and writes to tape once the server's storage
is becoming full.
Depending on your
requirements you can build your system using single P4 CPU with a
small storage or SMP CPUs server with tape library with hardware
compressing system connected to a SAN storage.
Also backup
procedure uses significant resources of slave servers and if your
servers are pretty loaded, you need would to choose configuration
that would finish daily backup within specific time. And because
writing to tape is usually much slower than collecting data from
servers, you will probably need a storage that would keep data of
daily backup to release servers' resources for your applications at
peak time.
Lets consider 3 levels of hardware of backup:
Entry level. Suitable for small number of servers (for example, 10-20 servers
with 100-200gb each) and if you don't have any limit for backup time.
In this case we can use single or dual CPUs systems with SATA
storage.
Medium level.
Recommended for 200-300 servers but if you still don't have any
limit for backup time. We would suggest to have 2-4 CPUs cores with
400-800GB SCSI storage. You would ask why SCSI is needed? You storage
must capable to transfer about 600-1000GB per day. Currently only
high-end hard drives (ie. SCSI) are capable to survive in this heavy
usage situation.
Enterpise level.Main difference between this solution and previous that your
system will be able to pull all data from slave servers to backup
from your servers within limited time so that backup procedure won't
degrade your servers' performance at peak time. For this
configuration you could use AHA362-PCIX hardware compression PCI-X
board that provides up to 3gbps compressing speed. To be able to save
compressed data at this speed you will need to have a SCSI storage
calculated by the following formula:
hNumber =
bSpeed/hSpeed
where
hNumber – number
of harddrives required for your storage
bSpeed – average
bandwidth of your backup system
hSpeed - average
write performance of hard drives
Lets say if you
want to backup your data at speed 1gbps, and your hard drives are
able to write data at 30Mb/s, you would need at least 5 hard drives.
Of course, higher number of hard drives allows you to write data at
higher speed. Because price of SAN storages with average 14 bays is
getting cheaper recently (about $2500 per for entry SAN storage), SAN
storage could be considered as most poweful and expandable solution
for backup server for its temporal storage.
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