Comments on: Linux Software RAID – A Belt and a Pair of Suspenders http://www.linux-mag.com/id/7475/ Open Source, Open Standards Sat, 05 Oct 2013 13:48:18 +0000 hourly 1 http://wordpress.org/?v=3.1 By: vu2lid http://www.linux-mag.com/id/7475/#comment-6872 vu2lid Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7475/#comment-6872 <p>Other interesting/useful GNU/Linux replication ideas:</p> <p>DRBD http://www.drbd.org<br /> (over tcp/ip, easy to setup High Availability if required)</p> <p>Unison http://www.cis.upenn.edu/~bcpierce/unison/<br /> (user-space, cross platform) </p> Other interesting/useful GNU/Linux replication ideas:

DRBD http://www.drbd.org
(over tcp/ip, easy to setup High Availability if required)

Unison http://www.cis.upenn.edu/~bcpierce/unison/
(user-space, cross platform)

]]> By: j3 http://www.linux-mag.com/id/7475/#comment-6873 j3 Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7475/#comment-6873 <p>Typo: \"These are /dev/sdb and /dev/sdb\" s/b \"These are /dev/sdb and /dev/sdc\" </p> Typo: \”These are /dev/sdb and /dev/sdb\” s/b \”These are /dev/sdb and /dev/sdc\”

]]> By: laytonjb http://www.linux-mag.com/id/7475/#comment-6874 laytonjb Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7475/#comment-6874 <p>@j3:</p> <p>Yep - good catch. I\'ll fix that typo later.</p> <p>Jeff </p> @j3:

Yep – good catch. I\’ll fix that typo later.

Jeff

]]> By: wodenickel http://www.linux-mag.com/id/7475/#comment-6875 wodenickel Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7475/#comment-6875 <p>I have an existing fakeraid 5 created from within Windows XP Home. Is it possible to access this from Ubuntu 9.04 using dm? My goal would be to dual boot & access it from both Win & Linux.</p> <p>thanks!<br /> GREAT ARTICLE - I read the docs but a worked example made it sink in. </p> I have an existing fakeraid 5 created from within Windows XP Home. Is it possible to access this from Ubuntu 9.04 using dm? My goal would be to dual boot & access it from both Win & Linux.

thanks!
GREAT ARTICLE – I read the docs but a worked example made it sink in.

]]> By: dbbd http://www.linux-mag.com/id/7475/#comment-6876 dbbd Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7475/#comment-6876 <p>The two articles, about LVM and about software raid, require a 3rd<br /> talking about the two in conjunction.<br /> To raid LVs or to PV raid groups? What is better? from performance, functionality and stability point of views?</p> <p>The article are good, introductions. I\'d like to see you going deeper. </p> The two articles, about LVM and about software raid, require a 3rd
talking about the two in conjunction.
To raid LVs or to PV raid groups? What is better? from performance, functionality and stability point of views?

The article are good, introductions. I\’d like to see you going deeper.

]]> By: laytonjb http://www.linux-mag.com/id/7475/#comment-6877 laytonjb Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7475/#comment-6877 <p>@dbbd:</p> <p>I\'m working on that article :) Determining which one is \"best\" is becoming somewhat subjective. In general, the best approach is to use RAID (md) on the lowest level and then use LVM on top of that. The simple reason is that you can expand the file system much easier using LVM than md. </p> <p>The questions I\'ve been examining become things such as,</p> <ul> <li>Do you split the drives into partitions and if so, how? </li> <li>How do combine the drives into RAID groups depending upon the RAID level? </li> <li>Do you use LVM for striping as well as md or is it one or other? </li> </ul> <p>So there are a bunch of considerations which makes the article much more difficult to write - I need to examine lots of options.</p> <p>Ultimately what I would like to produce is something of a \"contrast\" list. It will list the various approaches or ideas and then list the pros and cons because I think choosing the \"best\" is subjective (I haven\'t seen an article like this - have you?).</p> <p>Thanks for the feedback!</p> <p>Jeff </p> @dbbd:

I\’m working on that article :) Determining which one is \”best\” is becoming somewhat subjective. In general, the best approach is to use RAID (md) on the lowest level and then use LVM on top of that. The simple reason is that you can expand the file system much easier using LVM than md.

The questions I\’ve been examining become things such as,

  • Do you split the drives into partitions and if so, how?
  • How do combine the drives into RAID groups depending upon the RAID level?
  • Do you use LVM for striping as well as md or is it one or other?

So there are a bunch of considerations which makes the article much more difficult to write – I need to examine lots of options.

Ultimately what I would like to produce is something of a \”contrast\” list. It will list the various approaches or ideas and then list the pros and cons because I think choosing the \”best\” is subjective (I haven\’t seen an article like this – have you?).

Thanks for the feedback!

Jeff

]]> By: laytonjb http://www.linux-mag.com/id/7475/#comment-6878 laytonjb Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7475/#comment-6878 <p>@wodenickel</p> <p>I don\'t know if you can do that. I\'m guessing that it ill be very difficult. md would have to understand how Windows builds the RAID. Then Linux will have to understand the file system (if it\'s NTFS then read-only is fairly straight forward and you can use NTFS-3G for read/write).</p> <p>Did a google search turn up anything?</p> <p>Jeff </p> @wodenickel

I don\’t know if you can do that. I\’m guessing that it ill be very difficult. md would have to understand how Windows builds the RAID. Then Linux will have to understand the file system (if it\’s NTFS then read-only is fairly straight forward and you can use NTFS-3G for read/write).

Did a google search turn up anything?

Jeff

]]> By: lesatairvana http://www.linux-mag.com/id/7475/#comment-6879 lesatairvana Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7475/#comment-6879 <p>Thanks for this informative article. However, you say that \"you can now put a filesystem onto /dev/md0\". Actually, it has been my experience that you MUST put the filesystem onto /dev/md0 and NOT any drive used in the RAID. If you have two drives that you want in your RAID and you mkfs.ext3 each then when they are included in the RAID, the size of the filesystem will be larger than what the RAID can handle and you\'ll get \"attempt to write beyond end of device\". Doing mkfs-ext3 on /dev/md0 effectively puts a filesystem onto the whole RAID group but the number of available blocks is slightly smaller than the individual members could accomodate. </p> Thanks for this informative article. However, you say that \”you can now put a filesystem onto /dev/md0\”. Actually, it has been my experience that you MUST put the filesystem onto /dev/md0 and NOT any drive used in the RAID. If you have two drives that you want in your RAID and you mkfs.ext3 each then when they are included in the RAID, the size of the filesystem will be larger than what the RAID can handle and you\’ll get \”attempt to write beyond end of device\”. Doing mkfs-ext3 on /dev/md0 effectively puts a filesystem onto the whole RAID group but the number of available blocks is slightly smaller than the individual members could accomodate.

]]> By: laytonjb http://www.linux-mag.com/id/7475/#comment-6880 laytonjb Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7475/#comment-6880 <p>@lesatairvana:</p> <p>You are correct, sort of. If you want to stay with a simple RAID-1 with two disks, then yes you have to put the file system on /dev/md0. But you can also uses /dev/md0 as a building block for something else. For example, you can create /dev/md0 and /dev/md1 each from two pairs of disks, and then create a RAID-0 on top of that.</p> <p>Disclaimer - I\'ve never done this but I\'ve been told you can do it. (if I can get a couple more disks into my case, I will try it).</p> <p>Jeff </p> @lesatairvana:

You are correct, sort of. If you want to stay with a simple RAID-1 with two disks, then yes you have to put the file system on /dev/md0. But you can also uses /dev/md0 as a building block for something else. For example, you can create /dev/md0 and /dev/md1 each from two pairs of disks, and then create a RAID-0 on top of that.

Disclaimer – I\’ve never done this but I\’ve been told you can do it. (if I can get a couple more disks into my case, I will try it).

Jeff

]]> By: almac http://www.linux-mag.com/id/7475/#comment-6881 almac Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7475/#comment-6881 <p>More title than topic - in the UK, we\'d say \"a belt and braces approach\" - \"suspenders\" being the things which ladies used to hold up stockings, before the invention of tights. So what do you call those? I\'d like to know, my wife would like to know, but we don\'t want to get into porno hell trying to find out. She tells me. </p> More title than topic – in the UK, we\’d say \”a belt and braces approach\” – \”suspenders\” being the things which ladies used to hold up stockings, before the invention of tights. So what do you call those? I\’d like to know, my wife would like to know, but we don\’t want to get into porno hell trying to find out. She tells me.

]]> By: levonshe http://www.linux-mag.com/id/7475/#comment-6882 levonshe Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7475/#comment-6882 <p>Hi, thanks for the article. One thing I do not understand - why to synchronize disks before any data was put on them (even mkfs was done after sync)? </p> Hi, thanks for the article. One thing I do not understand – why to synchronize disks before any data was put on them (even mkfs was done after sync)?

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