Tell me how to spend my money!

[JamesR219]

Hello,

Ok, right now I have a 1.5TB array in a few year old linux box running RAID-5 w/ a hot spare (hot spare simply couldn't do 4*750GB in one array). It's a Adaptec 2410SA I think.

I previously had a ReadyNAS NV+, but found the backups to the external drives too slow and it was really underpowered for Rsync usage, which is what I normally use to perform backups. So, I sold it and moved to the RAID DAS to the linux box.

I am currently sitting at about 1TB of usage, and I figure now is a good time to upgrade and I get to make use of some Schedule 179 tax benefits before the end of the year.

I've been looking at NASes for a last few weeks and can't make up my mind what I want. I am wavering back and forth between setting up a DAS on the dedicated server I already have (8 bay and 3ware card) and getting some type of dedicated NAS.

So, my requirements are:

1. ~6TB of usable storage in a RAID-6 configuration. This should allow me to use this device for a few years without having to worry about it. I realize I will need to upgrade my backup storage as my usage increases, for will use 2TB drives for now.

2. Perform Versioned daily/monthly backups to an external drive (at first when under 2TB) or another NAS device. I typically do this with rsync with the --link-dest option to maintain hard links of files which haven't changed to the previous backup.

3. Backups must be performed during off-peak hours and finish in 6-8 hours.

4. Be able to receive daily backups of other servers using the rsync protocol over SSH. These are backups from remote offices running over SSH. This one requirement almost makes me want to stick with DAS.

5. Support Time Machine Backups from a few Mac Machines which are on the network. These are currently going to local disks on the individual machines which we would really like to get rid of.

I was going to pull trigger on QNAP 809, but I have posted some pre-sales questions in the forums and no replies after a few weeks. This is going to hold some important data and I need to be able to contact someone if things go south. Can't post in a forum and wait a week only to never hear back form someone.

I really like the concept of the NAS since it uses less energy and will make my office a little cooler. Right now its hot with all the computers in there.

I have a budget of about $3500 - $4500 to spend on this project including drives and backup media (like 2 x 2TB backup drives) which will give me 50% utilization on my backup from day 1 and hopefully in a year will just be about fill and I will migrate towards a NAS to NAS backup solution or simply use a bigger single disk if capacity has increased by then.

Thanks in advance for all your suggestions.

 

[thiggins]

So you want to backup ~1 TB daily and keep how many versions?

If my math is correct, you'll need 125 MB/s to back up 1 TB in 8 hours.
No NAS is going to give you that. Not even via eSATA.

 

[JamesR219]

So you want to backup ~1 TB daily and keep how many versions?

If my math is correct, you'll need 125 MB/s to back up 1 TB in 8 hours.
No NAS is going to give you that. Not even via eSATA.

Thanks for your reply.

Well, I would likely be doing it via rsync and not all 1TB is going to change every night. Right now my RSYNC (w/o checksum) takes about 45 mins. I run a weekly rsync w/ checksum and it takes about 12 hours.. That is fine though.

The versioning would be done via rsync --link-dest option, which basically just creates a hard link to previous backup and then only "unlinks" the changed files.

I am thinking more and more about just going with a DAS enclosure 8 drives setting up 5x2TB drives giving me 8TB of usable space raid 6 and then using remaining 3 slots as removable 2TB backup disks which I could rsync to and then unmount, remove and take off site. Any thoughts on this approach?

-jr

 

[thiggins]

Best rsync speed I've seen with any NAS is just shy of 70 MB/s backing up to an ext3 formatted eSATA drive (QNAP TS639 Pro).

Re your DAS plan, I might be a bit concerned with the long-term reliability of the SATA connections with so many connect/disconnect cycles.

You may have to go with your DAS plan. Someone else recently asked about backing up to internal drives not in the main array. I don't think that's an option with most NASes.

 

[JamesR219]

Best rsync speed I've seen with any NAS is just shy of 70 MB/s backing up to an ext3 formatted eSATA drive (QNAP TS639 Pro).

Re your DAS plan, I might be a bit concerned with the long-term reliability of the SATA connections with so many connect/disconnect cycles.

You may have to go with your DAS plan. Someone else recently asked about backing up to internal drives not in the main array. I don't think that's an option with most NASes.

That might have been me. Some have said it is possible by treating the NAS as a remote NAS and then just "updating it to itself".

I understand concern about the connect/disconnect cycles. You are thinking just about backplane/drive connection cycles, right?

Say I move it off site once per week.. That is ~50 cycles per year.. 250 cycles in 5 years. 1000 cycles in 20 years?

http://www.calgreg.com/circuit-assembly/sata-specification.pdf

Says "EIA 364-09 50 cycles for internal cabled application; 500 cycles for backplane/blindmate application. Test done at a maximum rate of 200 cycles per hour"

So, given the cable requirements. I think I would be good for 10 years or 500 cycles. Long past the useful lifetime of this hardware which I am pegging at 3-5 years.

The thing is I really don't need much performance in day-to-day use. It's just a file server for a handful of computers in a small office. I'm more concerned about keeping it backed up and safe.

Maybe I should just get 2 x 2TB drives and put them in external enclosure I already have on Mac Pro, set it up as raid 1 and re-evaluate everything in a year. Would give me 2x current space and cost *a lot* less.

-jr

 

[thiggins]

Good job on the calculation. You're right that the backplane connectors should be fine.

Sounds like DAS is the way to go for you.