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Re: [Lias] NAS/SAN storage recommendations?

Les Bell wrote:
"Ian Ralph" <ian@sceggs.nsw.edu.au> wrote:


After a few months the mainboard and 2 of the 4 IDE HDDs failed and it was
returned under warranty <lesson> Don't trust IDE drives for network
critical devices</lesson>.
<<

Although this is really an issue of quality, rather than architecture, I'd
generally agree. A lot of IDE drives have a quality level set by a target
low price. And no-one can accuse SCSI drive manufacturers of being driven
to pursue the low-cost end of the market. . .

Anyone noticed that the fastest IDE drives you can get are 7200 RPM? SCSI is all about performance and quality. If you need speed, you need SCSI. If you need reliable drives, you need SCSI. Having said that, if you have important data, you are nuts if you don't use raid.

The other problem with IDE is you can only have 4 IDE drives in a "normal" system. I'd recommend buying a couple of external drive enclosures that can whole 4 drives each (rack mount if you have it). Attach each external enclosure to a scsi controller and then raid the whole lot and mirror each enclosure against the other. This would give 4 x 72 = 288GB effective space and superb performance.

Does anyone have any other recommendations for tape backup?

Buy a flavour of DLT or LTO. DDS and most older tape technologies wrap the tape around a roller (just like video tapes) and stretch the tape making it unreliable over time. If possible, implement backup schemes so that "daily" tapes get promoted after only a few uses into a weekly and then further into monthly tapes. The idea being if you only use your tapes < 10 times or the like, then they are likely to still be in good condition.

At work we only have two pools of tapes: daily tapes and weekly tapes. New tapes go into the daily pool and weekly tapes get promoted as the oldest tape from the daily pool. The daily pool usually has 1-3 tapes per week (depends on the capacity) and we usually have around 4 to 5 months worth of dailys. As it turns out, we moved from DDS (2GB) to DLT (20GB) to DLT (40GB) to LTO1 (100GB) over the last 7 years. The DLT drives happened to use the same tape (DLT IV) and so we ended up recycling some weeklies after 18 months or so. Aside from that, the changes in tape technology have been at a pace that we haven't wanted to recycle old weeklies back.

Cost. Go get quotes on the different tape media and you will find that in general you get better $/GB as you get higher capacity tapes. So while staying within your budget, try to get the highest capacity tape technology you can. Similarly with tape drives, you will get better $/GB, smaller backup windows (probably not important in schools, but everyone knows the only reliable way to backup ANY DB is to do a backup with the DB shutdown), and fewer tapes. If you can afford it, autoloaders or libraries are good, but you should have at least two tape drives that can recover your data and possibly backup to both at the same time. If you end up wasting 1/2 a tape because your next backup will use 60% of a tape, you are wasting (cost of tape)/2. This can add up. If your backup SW can't estimate how much tape you have left, find something that can (this rules our dump and tar). The "big" tape drives will generally only come as SCSI.

Backup SW. If possible, you should find something that keeps online indexes. This means you can browse through a file system tree as it appeared 2 months ago and find the file that was only there for one day. Mark the file for recovery and the SW prompts you for the appropriate tape. We use Legato Networker at work, but while it is really good, its pretty expensive (I think the base product starts at around $5K). Amanda is another product that is free that I have heard good things about, but I have never used it and I'm not sure if it keeps online indexes (I suspect it does). It is also useful if the backup SW can use mulitple drives concurrently and backup multiple clients across the network to one or more drives.

Whatever solutions you choose, make sure you TEST your backups. Do complete recoveries from a whole tape onto a scrap area. There are numerous horror stories on the 'net for you to add to if you don't test your backups.

Hope that helps.

Regards,

Robert