Managing RAID on Linux

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Author: Derek Vadala
Binding: Paperback
EAN: 9781565927308
Label: O'Reilly Media, Inc.
Dimension: 0.71 x 9.13 x 7.01 inches
ISBN: 1565927303
Manufacturer: O'Reilly Media, Inc.
Publisher: O'Reilly Media, Inc.
Number of items: 1
Number of pages: 260
Publication date: December, 2002
Studio: O'Reilly Media, Inc.

Redundant Array of Independent Disks (RAID) technology is becoming a standard feature of computer systems that support mission-critical services like file sharing, mail exchange, or Web servers. RAID offers two benefits to these essential systems: improved I/O performance and fail-safe data storage. RAID has become the low-cost solution of choice to deal with the ever-increasing demand for data storage space. Managing RAID on Linux covers everything system administrators, power users, and tech managers need to know to put together a system that can support RAID. You will learn about the different types of RAID, along with associated technologies and issues, and how to choose the best RAID system for your needs. With a step-by-step, hands-on approach, the author guides you through the installation of either Linux software RAID or a hardware RAID card. The book shows how to build an array and optionally install a high-performance file system. Managing RAID on Linux sidesteps the often-confusing vendor-specific approach you'll find elsewhere to give you the straight story on RAID. Even non-Linux users will find this book full of valuable material.

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Ratings & Comments(Average:)

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- Will need Google if you want to recover from disk failure
I have to echo Lamar Thomas's review -- there is precious little on how to recover from a failed drive. You will have to go back to Google to learn how to recover from a single failed disk if using software raid to provide redundancy for your data. Having a paper reference for various types of disk recovery (in the case of not having a readily available web browser at the same site as the raid server machine) was the main reason I bought this book. So I was quite disappointed. Most of the book's material on hardware raid controllers is dated and by nature vendor specific. Moreover much of the material on creation of software raid that this book provides is unnecessary if one creates the raid partitions at installation.

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- Fairly good summary of Linux RAID information
Description

Some 230 pages that read easily. The first two chapters explain what RAID and the RAID levels are, what Linux offers, and compares software to hardware implementations. The third chapter gives detailed instructions on how to build a software RAID, using mdtools or mdadm. It tells you how to build the kernel with the right options, which may be unnecessary for you. There's some history of versions of the kernel, raidtools, mdadm. Furthermore, we get detailed information about creating arrays by hand, including hybrid arrays for combining the benefits of different RAID levels. The forth chapter gives a detailed reference about mdtools and mdadm, and the /proc pseudo-files provided by Linux. The fifth chapter presents some general issues of hardware RAIDs, and then goes into detail of five specific products. The sixth chapter is not about RAID at all: it gives an overview of the Linux filesystems. The last chapter is a mix containing managing RAIDs, configuring hard disks, performance, and booting. The book is rounded off by literature abd internet references. The book uses kernel 2.4.

Comment

By now we know that Linux is important. Linux software RAID comes for free and is fairly good. Therefore the book is justified. The book gives a good introduction explaining the RAID levels. The discussion about ATA versus SCSI is good. The comparison is an important complementary topic. The comparison between software and hardware implementations of RAID is good, too. The author expresses his opinion. I like my author to have an opinion. Vadala argues the case of software RAID in Linux. The material about filesystem discussion is okay, but not necessary here. As others have also noted, some topics must come earlier and clearer. For example a discussion of boot loaders. The material about fault detection and correction could be improved. On the whole, the book could be more problem-oriented.

Who should read it?

To set up a RAID, there's not much secret and the book will give you some added detail, but no big surprises. If you are a home user you probably don't need this book, although you might be curious. If you are a system admin, the book is useful as it resumes the tools necessary to create and manage RAIDs by hand and contains much information in gathered, well-presented form. Most of the information is available on the net.

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- Great intro to RAID
"Managing RAID on Linux" by Derek Vadala is a great intro and reference for understanding and setting up your own Linux RAID system at home or at work. The book does a great job of defining the terminology, covering the various RAID levels and explaining the technology. It covers both software as well as hardware RAID solutions, planning and tuning. The chapter on file systems was informative and the chapter on performance, tuning and maintenance was very useful.

This book would have been perfect a few years ago when I was setting up my current home file server which uses a pair of 40 GB drives in a software RAID-1 (mirroring) configuration. Since then, some of my partitions are now nearly full while others have plenty of free space. Rather than repartition, I've decided to build a replacement server with a RAID-5 configuration using three 120 GB drives.

While you can try and search the Internet for articles, I prefer reading from hard copy so I value books that do a good job of covering the material. This book came pretty darn close to addressing all of my questions except for one area.

At the time I ordered the book, a few people had mentioned "Linux Volume Management" which sounded very interesting. The copy I received was the first edition, dated December 2002, a time when LVM was itself relatively new. As such, there is no mention of LVM in this edition. Granted you'd almost need another book just to cover all of the details of LVM but since it is almost always used in concert with some kind of RAID, I felt the book should have had a section devoted to this important topic. Perhaps a chapter or two on this topic as well as a troubleshooting section could be added in a future edition.

The biggest difficulty with producing any book on Linux is that because it is constantly evolving, anything you write about can quickly become dated. I'd recommend this book as a good starting point for anyone interesting in learning about RAID on Linux especially if they come out with a 2nd edition with more info on LVM.

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- Don't count on this to help you recover!
I agree with all of the other reviews except the one that gave this book 5 stars! One of the most important topics that this book should have covered is how to recover from a disaster! How to replace a hard drive and re-sync the data to the new hard drive.

GURB is now an important boot loader and it doesn't even talk about it! Did you know that if you mirror (RAID 1) your drives during install and use GRUB as your boot loader your second disk won't boot if the first disk fails?

GURB doesn't copy the boot sector to the second (mirrored) disk during the RAID setup! You will be laboring under the mistaken thought that you will be ready *when* your system fails. What you don't know is that it is VERY hard to find out how to copy the boot sector to drive #2 using GURB. I still haven't found out after weeks of searching and posting in newsgroups.

If you can't recover from a failed drive, then you may as well NOT have a RAIDed system cause it wont do you any good. I can't believe that this book would leave a topic like that out! Just my two cents.

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- For RAID beginners that don't want to dig too deep
I was pretty diappointed by the content of that book.
The graphs and the explanations on what is RAID are nice, but there are only a few lines about what to do if something goes wrong, which is the kind of situation you would like to have a strong reference on how to save your data.

I would rate this book as ok for beginners, but when you want to know more, you don't have much help, so a bad mark for advanced users.
I expected a more advanced work like on the O'Reilly book 'Using Samba' which is very nice, especially the Troubleshooting section.

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