Zerowait Corporation

An Article worth reading in Computerworld

I have written about this issue many times before, but it seems that the Main Stream Tech Media is finally picking it up.

Most savvy enterprise storage customers understand that to get a decent ROI they need to get a usable life of at least 5 years. So, how come the big three storage vendors raise maintenance costs exponentially for systems that are more than 3 years old? A lot of our customers have read the big three’s ROI spreadsheets and calculations that show customers how if they spend hundreds of thousands now to replace their out of maintenance equipment with new, that over 3 years (the vendor desired life of the new equipment) that you’ll actually save money. Then they call Zerowait, and they see a whole new world on what ROI means.

The hardware vendors make money by forcing you to do a forklift upgrade after 3 years. Zerowait’s business model works because we help our customers extend their ROI calculations well beyond 3 years. When a customer extends their systems lifespan they also don’t need to purchase new or upgraded Backup software or monitoring software. There is no additional employee training, or implementation costs. Our customers save on maintenance costs and all of the secondary & tertiary costs also.

So how come vendors don’t include all of these additional infrastructure costs in their little spreadsheet from the marketing department? How much money would you save if you get 3rd party support (for a fraction of OEM support cost) and keep the old stuff around for another 2 years? Certainly that “enterprise class” system you bought 3 years ago is still a good system. It was enterprise class when you bought it, did it stop being enterprise class when the manufacturer’s new model came out?

Real Integrity is doing the right thing, knowing that nobody’s going to know whether you did or not – Oprah Winfrey

In the long run I think people figure out that certain companies have integrity and do the right thing over and over again. For instance, I like ordering from L.L Bean. I get what I want and satisfaction is guaranteed. My Dad used to order from them because once he got a shirt and somehow it was just not right, they took it back, and replaced it with a new one – no questions.

Working with High Availability technical equipment and storage we have to spend literally hundreds of hours documenting how we do some things so we can repeat them over and over again. This is because we need to constantly improve our processes and procedures as the technologies we work with change. Very few of our customers realize how much we do in the background to document, test and improve our procedures. But I think all of them recognize that the Zerowait staff is dedicated to providing them with the parts they need, and that the engineering support we provide will be excellent every time they call.

-- 

Character is much easier kept, than recovered. – Thomas Paine

Company reputations are gained and lost one customer at a time. Because our company deals with NetApp’s customers who have lost the faith, or can no longer afford the cost of NetApp maintenance we hear a lot of grumbling about NetApp. They come to Zerowait because they want an Affordable Alternative to NetApp that provides service, support and upgrades and can be depended on. And we work hard to build our reputation one customer at a time.

It saddens me to get a note from a NetApp customer trying to sell us his equipment that says ” …we have already purchased another SAN product, we would just like to put the NetApp behind us.”

When NetApp totally alienates a customer everyone loses. NetApp won’t get any more software revenue from the customer, the customer won’t have the great features a NetApp filer provides, and Zerowait won’t get a continuing service and support contract. It is one of the strange things about our business, the more business we do, the more OnTap software revenue NetApp gets to keep from our customers.

Getting together

This weekend there was a fly in and chili feast at a local grass strip (MD1). A whole bunch of us flew in. As you can see there was a great variety of aircraft on the field. And although the airplanes look a lot different from each other, when you get down to the engines and instruments , we all use the same parts from the same manufacturers. Although Cessna and Piper assemble them in different ways.

So the similarity with a storage network is there, the underlying bits and pieces all come from the same vendors. Hard drives, cards and so many other parts. But each of our diagrams is a little different.

Cross referencing parts can be interesting, but next time you are negotiating with your storage vendor ask them where they get the cards I’ll bet it’ s Intel and Qlogic. And the Hard drives are likely to be from Seagate.

” We simply can’t afford NetApp pricing and have moved in a different direction”

This is what a former NetApp customer told me as they were trying to sell us their old NetApp system which they loved. And since his Purchasing Agent did not write ‘ Transferable licenses required” on their PO when they purchased their system from NetApp, they only have a residual parts value.

So many people call us up after they have turned off their filers. They complain about the price of continuing maintenance from NetApp & how NetApp’s pricing forced them to move to another system. Although they love their filers, they have gone to an inferior product that is affordable.

When we speak to them and they hear that Zerowait provides an affordable alternative to NetApp for service and support they are quite dismayed, because they did not call us sooner. Before you give up on your filers CALL ZEROWAIT 888.811.0808 . We offer affordable service and support for NetApp.

Customer comments

On Monday, we had a customer call us up because they were having a NetApp problem in their New York City Data Center. They wanted us to take care of their problem for them because they are physically located in Russia.

We sent an engineer up on the train on Tuesday morning and took care of their problem. Taking care of problems with NetApp systems is what we do, so it all seemed pretty routine to us. Imagine how happy we were to receive the following comment from the customer via email this morning.

As of yesterday afternoon EDT, NYDR is back in operation.

I would like to point out the service we received from Zerowait was prompt,
flexible, and 100% professional -- they truly met our needs the best it can
be done. The downtime was minimized as much as possible.

Providing an affordable alternative to Netapp for Service, Support and Upgrades is what Zerowait specializes in, and we really appreciate it when customers notice.

It is always interesting to see who hits the Zerowait websites and Blog.

Lately NetApp ( nat-198.95.226.224..netapp.com ) has been stopping by a lot, and so has their attorneys Bowman and Brooke. (12.162.212.128) . The folks at Hitachi stop by a lot also (px2.hitachi.co.jp ) , we also see a lot of visits from EMC (psuedo-nat -29.isus.emc.com). The most popular site that people hit us from is www.netapp.org, and second is www.drunkendata.com. Google is the most popular search engine that sends people our way.

I am always amazed at the number of hits we get from overseas. And how many people are interested in my opinions. I appreciate your visits and also your comments, and I hope that you find my perspectives worthwhile. I remember that John Wanamaker said something like his advertising was 50% effective, he just did not know which 50%. Sometimes I feel the same way.

Zerowait and many of our customers will be at the summit. At Zerowait we use load balancing and mirroring to protect ourselves from data loss. Although, we also use our Spectra Logic library for a weekly backup. You can’t be too careful!

By the way, customers also need to be aware of the ways to cleanse their disks when they get ready to dispose of them. The other side of data protection is knowing how to cleanse your data.

I am not certain whether there will be a session on Disk cleaning techiques or not. But I hope that in the future these will be included. There are many aspects to data protection, this summit is a start in the right direction. I look forward to seeing you there!

Finally — An answer of sorts from NetApp on the BCS & ZCS issue

These answers below give a great perspective on the switch back to 512 sectors, from 520 sectors. And it is worth reading all the way through.

But I still think NetApp should release reliable, repeatable and verifiable performance data so that customers can make informed, economical business decisions based on the costs and risk factors of storing D/R data on ATA disk as compared to FC disk. Additionally, since there are costs associated with additional disks and wasted disk space due to the penalty of running Dual Parity disks to protect from a parity disk failure, customers need to know what are the percentages of wasted disk space and their costs in these configurations? Is it possible that because you don’t need to run DP with FC disks that in certain smaller raid configurations it could be cheaper to run FC than ATA on NetApp filers?

Finally, is there a read or write penalty to running databases on ATA disks with Dual DP and ZCS formatting, as compared to the faster Fibre channel disks with BCS formatting?

April 22nd, 2006 at 10:57 am
Cross Posted from the previous thread: From Dave Hitz, CTO, Network Appliance:
Let me take a shot at this. I asked one of our engineers to take a look at this thread as well, so if I mess up the details, hopefully he can set me right. (Hi Steve.)
Reformatting the disk drives from 512 bytes blocks to 520 byte blocks and putting the checksum right in each individual block is the best solution, because it doesn’t take any extra seeks or reads to get the chunksum data you need. This is called BCS or Block Checksum. (Most high-end storage vendors have something similar. EMC and Hitachi certainly do.)
Unfortunately, we aren’t able to format ATA drives with 520 byte blocks. Maybe someday, but not yet. So with ATA we use a different technology called Zoned Checksum (or ZCS) where we steal every Nth block on the disk and use it for the checksums. (I think N is 64, but can’t remember for sure.) This is less efficient because you have to read extra data, but it allows you to get the reliability benefits of checksums even with ATA drives, which is important because ATA drives are less reliable.
And what about the RAID-DP (DP = “double parity”)? I think that RAID-DP is a wise choice for all drives, Fibre Channel or ATA, but given that ATA drives are less reliable we make RAID-DP the default there. I’m wondering if it’s time to make it the default for Fibre Channel drives as well, but as far as I know, we haven’t done that yet.
Why sell less reliable drives? ATA drives are cheaper! If you’ve got the money, then by all means keep buying Fibre Channel drives and keep using block checksums.
On the other hand, if you want to save money, and your application can get by with a bit less performance, then the combination of RAID-DP and Zoned Checksums can make ATA drives very safe. We used to recommend ATA only for disk-based backup or for archival storage, but now that we have RAID-DP and ZCS, we see lots of customers using it for primary storage, which is why we are starting to support ATA through the entire product line, and not just in the R-Series.

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1. Steve Strange Says:
   April 22nd, 2006 at 2:36 pm

   Let me see if I can fill in a few more details (Hi Dave).

   First, let me try to clear up the confusion about BCS vs. ZCS, and provide a little history. As Dave says, ZCS works by taking every 64th 4K block in the filesystem and using it to store a checksum on the preceding 63 4K blocks. We originally did it this way so we could do on-the-fly upgrades of WAFL volumes (from not-checksum-protected to checksum-protected). Clearly, reformatting each drive from 512 sectors to 520 would not make for an easy, on-line upgrade.

   As Dave says above, the primary drawback to ZCS is performance, particularly on reads. Since the data does not always live adjacent to its checksum, a 4K read from WAFL often turns into two I/O requests to the disk. Thus was born the NetApp 520-byte-formatted drive and Block Checksums (BCS). For newly-created volumes, this is the preferred checksum method. Note that a volume cannot use a combination of both methods — a volume is either ZCS or BCS.

   Pq65 provides some spare-disk output from a filer running ONTAP 7.x showing spares that could be used in either a BCS or a ZCS. The FC drive shown here is formatted with 520-byte sectors. If it is used in a ZCS volume, ONTAP will simply not use those extra 8 bytes in each sector.

   When ATA drives came along, we were stuck with 512-byte sectors. But we wanted to use BCS for performance reasons. So rather than going back to using ZCS, we use what we call and “8/9ths” scheme down in the storage layer of the software stack (underneath RAID). Every 9th 512-byte sector is deemed a checksum sector that contains checksums for each of the previous 8 512-byte sectors (which is a single 4K WAFL block). This scheme allows RAID to treat the disk as if it were formatted with 520-byte sectors, and therefore they are considered BCS drives. And because the checksum data lives adjacent to the data it protects, a single disk I/O can read both the data and checksum, so it really does perform similarly to a 520-byte sector FC drive (modulo the fact that ATA drives have slower seek times and data transfer/rotational speeds).

   Starting in ONTAP 7.0, the default RAID type for aggregates is RAID-DP, regardless of disk type. For traditional volumes, the default is still RAID-4 for FC drives, but RAID-DP for ATA drives. You cannot mix FC drives and ATA drives in the same traditional volume or aggregate.

   The default RAID group size for RAID-DP is typically double the number of disks as for RAID-4, so if you are deploying large aggregates, the cost of parity is quite similar for either RAID type. But the ability to protect you from a single media error during a reconstruct is of course far superior with RAID-DP (the topic of one of Dave’s recent blogs on the NetApp website).

   You can easily upgrade a RAID-4 aggregate to RAID-DP, or downgrade a RAID-DP aggregate to RAID-4. But you cannot shrink a RAID group, so you do want to be careful about how you configure your RAID groups before you populate them with data (assuming you don’t like the defaults).

   There was an implication earlier in this blog that we used to use RAID 4, but on newer systems we use RAID 5. That’s not the case — we do not use RAID 5 on any of our systems (though an HDS system sitting behind a V-series gateway might use it internally). This is a whole topic in itself, but the reason, stated briefly, is that RAID-4 is more flexible when it comes to adding drives to a RAID group, and because of WAFL, RAID-4 does not present a performance penalty for us, as it does for most other storage vendors. RAID-DP looks much like RAID-4, but with a second parity drive.

   Our “lost-writes” protection capability was also mentioned. Though it is rare, disk drives occasionally indicate that they have written a block (or series of blocks) of data, when in fact they have not. Or, they have written it in the wrong place! Because we control both the filesystem and RAID, we have a unique ability to catch these errors when the blocks are subsequently read. In addition to the checksum of the data, we also store some WAFL metadata in each checksum block, which can help us determine if the block we are reading is valid. For example, we might store the inode number of the file containing the block, along with the offset of that block in the file, in the checksum block. If it doesn’t match what WAFL was expecting, RAID can reconstruct the data from the other drives and see if that result is what is expected. With RAID-DP, this can be done even if a disk is currently missing!

   We’re constantly looking for opportunities for adding features to ONTAP RAID and WAFL that can hide some of the deficiencies and quirks of disk drives from clients. I think NetApp is in a unique position to be able to do this sort of thing. It’s great to see that you guys are noticing!

   Steve

2. Administrator Says:
   April 22nd, 2006 at 3:56 pm

   Wow: great historical and technical clarification. My hat is off to Dave and Steve for jumping to the task of helping clear up the confusion around this 512/520 issue.

   Truly appreciated by all.

I agree with Jon on this, I guess it is my turn to invite Dave out for dinner to thank him for clarifying the issues so well.

The ZCS(512) & BCS(520) Saga continues

Jon Toigo asked me to respond to a post on his blog .

Hi Jon:

I find PQ65’s comments very interesting, but I don’t understand the reasoning behind his comments. If BCS (520) is better then ZCS (512) and NetApp uses ZCS on their Nearstore products, doesn’t this mean that customers D/R and backup drives are more vulnerable to corruption? It would seem so, because NetApp recommends Dual Parity on ZCS drives. This seems to leave customers relying on a less resilient technology for their backups. How much less reliable are ZCS systems than BCS systems, and is it worth the risk? That is what my customers and I are trying to find out.

Can NetApp provide reliable, repeatable and verifiable data to show their consumers that the Nearstore products that use ZCS drives are as reliable as NetApp’s products that use BCS technology? Does NetApp keep its financial data on ZCS drives or BCS drives? Why not allow consumers to judge their cost to risk ratio by disclosing test results that can be duplicated and verified?

Clearly there are performance and cost advantages to each technology and drive type. NetApp could easily disclose accurate and repeatable test results, consumers could then make informed and economical decisions on where to store their D/R and back up data. And everyone would be a winner.