2011-04-13 10:57 AM
We just published a white paper on the NetApp Virtual Storage Tier. The intent here is to show how intelligent caching provides a level of "virtual tiering" without the need to physically move any data among HDD types.
Hope this sheds some light on our approach.
2011-04-14 01:59 AM
Most people don't realize that compellent autotiers SNAPPED data, NOT production data!
Yep, I wasn't aware of this either. If that's the case then why actually Dell bought them? Didn't they notice that?
So how about 3Par autotiering? Marketing-wise they are giving me hard time recently, so I would love to discover few skeletons in their cupboard too!
2011-04-14 03:10 AM
Is the problem in the way they do it or the granularity of the block?
There is talk that Dell/Compellet will move to 64bit software soon, thus enabling them to have smaller blocks and then the granularity will problably not be a problem.
You could turn the argument around and say that Ontap never tiers down (transparently) snapshots to cheaper disk, no matter how seldom you access it.
So you will be wasting SSD/FC/SAS disk for data that you might, maybe, need once in a while.
2011-04-14 03:20 AM
Well … I guess, NetApp answer to this would be snapvault,
For me one of main downsides of NetApp snapshots is inability to switch between them – volume restore wipes out everything after restore point; and file restore is unacceptable slow (which I still do not understand why) and not really viable for may files.
CLARiiON can switch between available snapshots without losing them. Not sure about Celerra, I do not have experience with their snapshot implementation.
2011-04-14 03:43 AM
From what I'm told with snapvault the users loose the possibility of doing "previous versions" restore from snapvaulted snapshots of the files, right?
So the "transparently" thing is kicking in and a system administrator has to be involved, with all the extra work and time it takes to restore a file.
2011-04-14 03:56 AM
That’s true (except that previous versions does not work with block access anyway).
Does it (previous versions from snapshots) work with other vendors for SMB? Celerra in the first place (given we discuss VNX)?
2011-04-15 09:03 AM
The granularity is part of the problem (performance is the other). Page size is 2MB now, if you move it to 512K the box can't grow.
With the 64-bit software they claim they might be able to go real small like 64K (unconfirmed) but here's the issue...
The way Compellent does RAID with pages is two-fold:
It follows that for RAID-1 the 64K page could work (64K written per drive - reasonable), but for RAID-5 it will result in very small pieces going to the various drives, not the best recipe for performance.
At any rate, this is all conjecture since the details are not finalized but even at a hypothetical 64K if you have random modifications all over a LUN (not even that many) you will end up using a lot of snap space.
The more stuff you have, the more this all adds up.
My argument would be that by design, ONTAP does NOT want to move primary snap data around since that's a performance problem other vendors have that we try very, very hard to avoid. Creating deterministic performance is very difficult with autotiering - case in point, every single time I've displaced Compellent it wasn't because they don't have features. It was performance-related. Every time.
We went in, put in 1-2 kinds of disk + Flash Cache, problem solved (in most cases performance was 2-3x at least). It wasn't even more expensive. And THAT is the key.
Regarding Snapvault: it has its place, but I don't consider it a tiering mechanism at all.
I wish I could share more in this public forum but I can't. Suffice it to say, we do things differently and as long as we can solve your problems, don't expect us to necessarily use the same techniques other vendors use.
For example, most people want
If we can do all 4 for you, be happy but don't dictate HOW we do it
2011-07-01 11:09 AM
EMC doesn't have Metrocluster in the VNX, but offers VPLEX Metro as an equivilent configuration. VNX + VPLEX can be the same cost as a NetApp Metrocluster. With their 5.0 code, they have transparent failover (no similair "cf takeover" command), if you install a witness at a third site running in a VM or standalone server.
It would be good for NetApp to offer similiar witness support to handle the total datacenter failure/split-brain scenerio. I'm currently comparing NetApp MetroCluster and EMC VPLEX Metro in my own blog http://dctools.blogspot.com.
No one ever has it all. EMC's VPLEX will rely on VNX or RecoverPoint to do snapshots. NetApp has snapshots nicely integrated into one package. NetApp doesn't offer redundent nodes at each datacenter, EMC VPLEX does. NetApp MetroCluster will have storage traffic trombone, EMC VPLEX will offer local access at each site.
The point is, no one vendor has everyone. Most are wearing blinders to what other's can do and their own limitations. I would love NetApp to offer sub-lun tiering within an aggregate. I would love NPIV-style virtual target FC ports into a vFiler. I would love NetApp to offer a web-based GUI to all the administrative commands people use (vFiler...).
VNX may have two different OSes for block and NAS, but customers don't usually see it or have to learn it, as Unisphere covers that up.
I am a huge NetApp fan and sell a lot of NetApp boxes. They work well. They offer some of the richest functionality, but the user interface (GUI, web-based) is often lacking in NetApp's best features.
2011-07-01 12:28 PM
Most disk storage vendors have support through previous versions.
Saying SnapVault is the answer is like saying RAINfinity is auto-tiering. It's a seperate poorly integrated product/option/feature.