tapeless solution - DISK versus FILE

[r.kennedy]

We have a tapeless nearline solution for our data storage, remotely mirrored offsite.



What is the practical difference between just having primary DISK pools and creating a FILE-based devclass stgp? All I can figure is that one of them I will have to reclaim, and the other I don't. Is there an advantage to the FILE solution that I'm not seeing?

 

[heada]

One more advantage of the diskpool based system is the ability to use raw logical volumes. Creating raw volumes is MUCH faster that normal volumes and it seems to me that read/write operations(via direct I/O) happen faster them them as well.



-Aaron

 

[moon-buddy]

Cost?



Disk based solution is expensive as the volume of data increases. However, if you definitely know that you will not exceed you initial design levels (capacity), then disk based is faster and better.



File based offers robustness where disk based solutions falls short on. Disk crashes will be often, maybe in the magnitude of 1000 to 1, than file based crashes.



Just my two cents ...

 

[moon-buddy]

Cost?



Disk based solution is expensive as the volume of data increases. However, if you definitely know that you will not exceed you initial design levels (capacity), then disk based is faster and better.



File based offers robustness where disk based solutions falls short on. Disk crashes will be often, maybe in the magnitude of 1000 to 1, than file based crashes.



Just my two cents ...

 

[heada]

Would not the number of hardware issues be exactly the same as you have to store the files on a disk somewhere? Raw logical volumes are just volumes on disk and files are just files in a filesystem on disk. If you are using a journaling filesystem, you have an added safty net but you also have the overhead of the journal. With proper hardware (HP EVA, EMC DMX/DMX3, IBM ESS) losing a disk or two can happen and no one would even know (I've lost 4 disks at the same time across multiple arrays in an ESS 800 and didn't know until IBM showed up to replace them)



Most people I know that are looking at purely disk based systems(raw or file) are doing so for speed. When you require the speed of disk for your backup, it is assumed that you will be paying more than if you were using tape.



Personally, I like the feeling I have by being able to walk out of the datacenter with 4 3592 tapes in my hand and know I'm carrying 3+TB....but thats just me.



-Aaron