Home > Ask the Storage Technology Experts > Questions & Answers > Advice when researching NAS devices
Ask The Storage Expert: Questions & Answers
EMAIL THIS

Advice when researching NAS devices

Randy Kerns EXPERT RESPONSE FROM: Randy Kerns

Pose a Question
Other Storage Categories
Meet all Storage Experts
Become an Expert for this site
>
QUESTION POSED ON: 18 April 2003
I've been doing some research on NAS devices lately. One of the nice features touted by NetApp, that I'd like to make use of, is SnapShot.

I've spoken to NetApp about this feature. They compare their snapshot technology to other vendors saying theirs is superior since on a block change, the original block is not moved, a new block is written and the pointer is updated. The old block is kept around as long as the snapshot is kept around.

Conversely, other vendors have a snapshot swap space where when a snapshot is taken any changes to the block result in the following. The original block is copied to the swap space and the original block is overwritten, resulting in two physical writes for every logical writes. However, these vendors seem to think these writes won't cause much overhead. Also they point out that the WAFL file system on a NetApp filer will eventually become very fragmented causing a performance hit at about 70%-80% capacity.

Can you shed any light on the two options presented above?


>

You need to always be careful when you get negative marketing. Negative marketing is where a vendor says bad things about a competitor's product rather than saying what's good about theirs and let you make the decision. When I hear negative marketing, I usually ask the person to stop and if they persist, either I leave or they do. It usually comes from a person that is really not competent that is doing the negative marketing and it takes just a few seconds with appropriate questions to expose them. At any rate, they are wasting your time.

Now to answer the question, NetApp does use a log-structure file system (which they call WAFL) that allows them to use pointers to connect the information for file systems (which equal a LUN in this case). A snapshot for NetApp just involves pointer manipulation so there is a minimal amount of overhead and no extra disk space consumed.

The SnapRestore is an interesting function in that the file system is a read-only copy. There are more details on the NetApp Web site that you can read to get the details. A log-structured file system is targeted at writing data at the next available location to minimize electro-mechanical motion on the disk (and thereby same time). There is potential for the next available location to be in disparate places requiring some movement but on average it will be much better than always seeking to a new location. Free space collection to provide localized, contiguous blocks would be a background task that could improve performance somewhat and NetApp will be very likely adding that in the future.

Right now, the competitor's claims are saying it's not optimal and kind of a strange negative marketing statement. I wouldn't be concerned, if it provides the performance you need.

Randy Kerns
Evaluator Group, Inc.

Editor's note: Do you agree with this expert's response? If you have more to share, post it in one of our discussion forums.


Digg This!    StumbleUpon Toolbar StumbleUpon    Bookmark with Delicious Del.icio.us   



RELATED RESOURCES
2020software.com, trial software downloads for accounting software, ERP software, CRM software and business software systems
Search Bitpipe.com for the latest white papers and business webcasts
Whatis.com, the online computer dictionary



Search and Browse the Expert Answer Center
Search and browse more than 25,000 question and answer pairs from more than 250 TechTarget industry experts.
Browse our Expert Advice



Search for Data Management Tools
TechTarget Storage Media
Storage Magazine View this month\\'s issue and subscribe today.
Storage Decisions Apply online for free conference admission.
SearchStorage.com
HomeNewsMagazineTopicsLearningMultimediaWhite PapersBlogsEventsAbout Us

About Us  |  Contact Us  |  For Advertisers  |  For Business Partners  |  Site Index  |  RSS
TechTarget provides technology professionals with the information they need to perform their jobs - from developing strategy, to making cost-effective purchase decisions and managing their organizations' technology projects - with its network of technology-specific websites, events and online magazines.

TechTarget Corporate Web Site  |  Media Kits  |  Site Map




All Rights Reserved, Copyright 2000 - 2009, TechTarget | Read our Privacy Policy
  TechTarget - The IT Media ROI Experts