Is your backup server a modern, state of the art machine with high speed disk, significant IO throughput capabilities and ample RAM so as to not be a bottleneck in your environment?
If not, why?
Given the nature of what it does – support systems via backup and recovery – your backup server is, by extension, “part of” your most critical production server(s). I’m not saying that your backup server should be more powerful than any of your production servers, but what I do want to say is that your backup server shouldn’t be a restricting agent in relation to the performance requirements of those production servers.
Let me give you an example – the NetWorker index region. Using Unix for convenience, we’re talking about /nsr/index. This region should either be on equally high speed drives as your fastest production system drives, or on something that is still suitably fast.
For instance, in much smaller companies, I’ve often seen the production servers have SCSI drives or SCSI JBODs, but the backup server just be a machine with a couple of mirrored SATA drives.
In larger companies, you’ll have the backup server connected to the SAN with the rest of the production systems, but while the production systems will get access to 15,000 RPM SCSI drives, the backup server will get instead 7,200 RPM SATA drives (or worse, previously, 5,400 RPM ATA drives).
This is a flawed design process for one very important reason – for every file you backup, you need to generate and maintain index data. That is, NetWorker server disk IO occurs in conjunction with backups*.
More importantly, when it comes time to do a recovery, and indices must be accessed, do you want to pull index records for say, 20,000,000 files from slow disk drives or fast disk drives?
(Now, as we move towards flash drives for critical performance systems, I’m not going to suggest that if you’re using flash storage for key systems you should also use it for backup systems. There is always a price point at which you have to start scaling back what you want vs what you need. However, in those instances I’d suggest that if you can afford flash drives for critical production systems, you can afford 15,000 RPM SCSI drives for the backup servers’ /nsr/index region.)
Where cost for higher speed drives becomes an issue, another option is to scale back the speed of the individual drives but use more spindles, even if the actual space used on each drive is less than the capacity of the drive**.
In that case for instance, you might have 15,000 RPM drives for your primary production servers, but the backup servers’ /nsr/index region might reside on 7,200 RPM SATA drives successfully, so long as they’re arrayed (no pun intended) in such a way that there’s sufficient spindles to make reading back data fast. Equally then, in such a situation, hardware RAID (or software RAID on systems that have sufficient CPUs and cores that it equals or exceeds hardware RAID performance) will allow for faster processing of data for writing (e.g., RAID-5 or RAID-3).
In the end, your backup server should be like a butler (or a personal assistant, if you prefer the term) – always there, always ready and able to assist with whatever it is you want done, but never, ever an impediment.
* I see this as a similar design flaw to say, using 7,200 RPM drives as a copy-on-write snapshot area for 15,000 RPM drives.
** Ah, back in the ‘old’ days, where a database might be spread across 40 x 2GB drives, using only 100 MB from each drive!