Lvm striping-Pick Your Pleasure: RAID-0 mdadm Striping or LVM Striping? - Linux Today Blog

Red Hat's documentation publication system recently went through an upgrade to enable speedier, more mobile-friendly content. We decided to re-evaluate our commenting platform to ensure that it meets your expectations and serves as an optimal feedback mechanism. During this redesign, we invite your input on providing feedback on Red Hat documentation via the discussion platform. Creating Striped Volumes. When you create a striped logical volume, you specify the number of stripes with the -i argument of the lvcreate command.

Lvm striping

Lvm striping

Lvm striping

Lvm striping

Lvm striping

In example 1 the stripe width is 2. Save my name, email, and website in this browser for the next time I comment. Here are the performance numbers between linear and striped logical volumes. Once one devices is full, it flows over to the striiping, etc. The real goal of this episode was to teach the difference between linear and striped logical volumes and I think we have done that so far. Layton on May Smart and sexy women,Lvm striping Comments 0. Step by step installing an Identity Lvm striping server in Linux using At this point, you can see that all of our SSD disks are getting exercised.

Bust a move bash. If You Appreciate What We Do Here On TecMint, You Should Consider:

For example, if you have a two-way stripe that uses up an entire volume group, adding a single physical volume to the volume group will not enable dtriping to extend the stripe. Another issue is IOPS. It is this flexibility that allows you to do data striping. Unlike tests from previous articles, each test was only run 1 time using ext4. There are also some issues with the way I did today tests. Ending In: 3 days. In practice, stripinf HA-LVM configuration works as an "anti-ignorance interlock" too: even regular Linux-savvy sysadmins who haven't Read The Fine Manual about cluster configurations are usually Lvm striping unaware of VG tags and their effects Because different segments of data are kept on different storage devices, the failure of one device Lvm striping the corruption of the full data sequence. You did a Lvm striping -a n volgroup. Tags: lvm. In this example, the first data piece, A1, is sent to disk 0, the second piece, A2, is sent to disk 1, and so on.

Given the price of hard drives and the number of drives you can put into a single system albeit a desktop or a server, a very common question is how to arrange the drives to improve performance.

  • Go to Solution.
  • By using our site, you acknowledge that you have read and understand our Cookie Policy , Privacy Policy , and our Terms of Service.
  • In this episode, I wanted to look at the performance characteristics between linear and striped logical volumes using LVM.
  • LVM Striping is one of the feature which will writes the data over multiple disk, instead of constant write on a single Physical volume.
  • Given the price of hard drives and the number of drives you can put into a single system albeit a desktop or a server, a very common question is how to arrange the drives to improve performance.

In this episode, I wanted to look at the performance characteristics between linear and striped logical volumes using LVM. We will examine what is happening behind the scenes along with some preliminary benchmarks using an AWS i2. Lets say for example that you have a requirement for an extremely fast storage subsystem on a single machine. But for today, lets say you have narrows the selection down to LVM.

So, do you choose to use LVM linear and striped logical volumes and which one has the best performance? The machine type is an i2. I should note that when using LVM striped logical volumes, typically the more disks you have, the better performance you will see. I was originally going to use the AWS hs1. For example, it could take 8 or more hours to pre-warm the disks on this instance type since it has 24 disks. I just wanted to highlight this in case you wanted to replicate my results on similar AWS hardware.

Lets briefly review what the system looks like before we get on with the demo. We are going to be using Ubuntu Here is what the mounts look like along with our 8GB OS disk which we talked about earlier. At a high level here is what our design is going to look like. Now that we have the prerequisites installed, and I have given you an overview of the designs, lets run pvdisplay to verify we have no physical volumes configured.

We can verify this worked by running vgdisplay. At this point we pretty much have things configure so we can dive into the demos. By the way, the b through i, in those boxes under the linear and striped headings, are my attempt to display the physical volume SSD devices. Next, lets verify it worked by running lvdisplay.

Today, I am going to use XFS since it is used in many large scale computing environments and allows you to quickly create a filesystem over a large chunk of disk, in our case, roughly 6TB. Lets run mkfs. At this point we are ready to do some benchmarking. I am going to open two terminal windows. In the first terminal window, we will run the bonnie benchmark software, then in the second we can monitor the SSD disk activity.

The hope is that we can differentiate linear vs striped logical volumes both by the disk activity and benchmark results. Okay, so lets get the bonnie benchmark software sorted out first. I found this pretty nice blog posting about how to run bonnie benchmarks along with a useful chain of commands to run. I have linked to this site in the episode notes below if you are interested in reading more. Basically, we are running the bonnie benchmark software, along with taking into account the amount of RAM the machine has, making sure that we write well above the limit, in this case, we are going for twice the amount of RAM.

The reason for this, is that we do not want to system to cache our benchmark in RAM, thus blowing the results. Before I start the benchmark, lets jump over to the second terminal, here we are going to watch the SSD disk activity to see how the reads and writes are spread across the disks.

While doing research for this episode, I came across a very useful utility called bwm-ng, and we will use this tool to monitor reads and writes to each SSD device. I have pasted the exact bwm-ng command in the episode notes below. We are finally ready to run our benchmark now that we have the command ready to go and our monitoring pointed at the SSD devices.

Lets start the benchmark in the first window, then jump over to the second window, where we have the monitoring software running. I should mention, that the entire benchmark took over an hour to run, so you are seeing a heavily edited summary. Well, it is probably best described through a series of diagrams. When using liner logical volumes, you are essentially connecting these devices in series or daisy chaining them together. So, the reads and writes happen like this. Once one devices is full, it flows over to the next, etc.

Kind of like a water fall effect. So, in this example, even though we have 8 SSD devices, our benchmark is only hitting the first device! Okay, now that we have our results and know a little about how linear volumes work, lets move onto how striped volumes work.

But first, lets clean up the linear volume, by unmounting the disk. Okay, so lets just jump back to the diagrams for a minute.

Easy enough right, and you will notice this command looks almost exactly the same as the earlier version, just with the added stripes and stripesize options.

These rather simple options dramatically change the performance profile as we will see in a minute. I just wanted to mention that it is not always clear by looking at lvdisplay whether you are running in linear or striped mode.

You can see that the default lvdisplay output does not tell you anything interesting in that regard. You can use lvs segments to give you a little information about the logical volume, but if you are looking for detailed information about the logical volume, try running lvdisplay -vm, as you can see there is a bunch of output, lets just scroll up here.

So, we have our default output about the volume up top, then down here, we have detailed info about the stripe size and the devices which back it. Just as we did last time, lets go ahead and create a filesystem on this device by running, mkfs. Finally, lets verify it is mounted correctly.

Just as we did last time, lets configure the bonnie benchmark to run in the first terminal window, and use the second for the disk monitoring software. Lets just quickly hop over to the second window and verify there is no disk activity before running the benchmark command. Looks good, so lets execute the benchmark and then watch the disk activity. At this point, you can see that all of our SSD disks are getting exercised.

While doing research for this episode, it was explained that writes go to the disks in a round-robin fashion, and as you can see, this certainly seems to be the case, and this time around the benchmark completed much more quickly because we are actually using all of the disks. So, lets just recap with a couple diagrams and some closing notes.

Linear volumes, like we saw in the earlier example, write to the disks in series, as one disk fills up, the next fills, and so on. This is in comparison to how striped logical volumes work. With striped logical volumes, writes head to the disk in a round-robin fashion, so you will actually see much better performance because you are using more disks, and not creating hot spots, or saturating one disk in the array.

This is probably a good place to leave this episode, as I think this one slide highlights the entire discussion. However, our results do raise some interesting questions, these are ones that you will likely run into too, if you venture down this path. Here are the performance numbers between linear and striped logical volumes. As you can see, striped logical volumes absolutely kill linear volume types.

What is interesting, is that I expected to see higher numbers, specifically for sequential reads for the striped volume type. AWS is a bit of a black box, in that if we had physical hardware, we could play around with various typologies to see if we can get better performance.

Personally, I think we are saturating some type of link, but this is hard to diagnose without knowing the typology layout, or having access to the physical hardware. The real goal of this episode was to teach the difference between linear and striped logical volumes and I think we have done that so far. But, if I was to implement this for a project I was working on, there are likely other bits I would want to test and profile. For example, try hardware typology designs to make sure you have IO channel separation and are not saturating a link somewhere.

Try other filesystems or maybe try and align LVM stripe and filesystem block sizes. What about tuning for your specific workload? There are also some issues with the way I did today tests. The disk activity monitoring might throw off our benchmarks, also maybe XFS was not a good filesystem choice. Not to mention, that if this was for a real project, I would have run multiple bonnie tests and averaged the results, but since this is just an illustration, I did not want to spend too much money on running the AWS instance for long periods of time.

Personally, this episode highlights what I love about Amazons Cloud Computing platform. Typically, as a sysadmin you will often be asked to spec something out for a particular project without having hardware.

You are essentially guessing, hoping, and then praying that the hardware you spent tens of thousands of dollars on will meet your needs. But with AWS, you can fire up a beefy instance, test your ideas, and then come up with a working plan, typically within hours. As was demonstrated today, we used hardware which typically costs many thousands of dollars for several hours to test some ideas, which ultimately allowed us to get a firm idea of what we can expect on this hardware.

Writing intelligently Version 1. Get Notified. You may also like Nomad 74 - How to Create Architecture Diagrams 62 -

I have linked to this site in the episode notes below if you are interested in reading more. Check Stripe Size. Email Required, but never shown. LVM takes the first few stripes from the first physical volume PV0 and maps them to the first stripes on the logical volume LV0. Related 0. Striped Logical Volumes. If you are familiar with logical volume you can go head to setup the logical volume stripe.

Lvm striping

Lvm striping

Lvm striping

Lvm striping

Lvm striping

Lvm striping. Your Answer

Striping enhances performance by writing data to a predetermined number of physical volumes in round-round fashion. In some situations, this can result in near-linear performance gain for each additional physical volume in the stripe.

The following illustration shows data being striped across three physical volumes. In this figure:. In a striped logical volume, the size of the stripe cannnot exceed the size of an extent. Striped logical volumes can be extended by concatenating another set of devices onto the end of the first set. I found this pretty nice blog posting about how to run bonnie benchmarks along with a useful chain of commands to run.

I have linked to this site in the episode notes below if you are interested in reading more. Basically, we are running the bonnie benchmark software, along with taking into account the amount of RAM the machine has, making sure that we write well above the limit, in this case, we are going for twice the amount of RAM.

The reason for this, is that we do not want to system to cache our benchmark in RAM, thus blowing the results. Before I start the benchmark, lets jump over to the second terminal, here we are going to watch the SSD disk activity to see how the reads and writes are spread across the disks. While doing research for this episode, I came across a very useful utility called bwm-ng, and we will use this tool to monitor reads and writes to each SSD device.

I have pasted the exact bwm-ng command in the episode notes below. We are finally ready to run our benchmark now that we have the command ready to go and our monitoring pointed at the SSD devices.

Lets start the benchmark in the first window, then jump over to the second window, where we have the monitoring software running. I should mention, that the entire benchmark took over an hour to run, so you are seeing a heavily edited summary. Well, it is probably best described through a series of diagrams. When using liner logical volumes, you are essentially connecting these devices in series or daisy chaining them together. So, the reads and writes happen like this.

Once one devices is full, it flows over to the next, etc. Kind of like a water fall effect. So, in this example, even though we have 8 SSD devices, our benchmark is only hitting the first device! Okay, now that we have our results and know a little about how linear volumes work, lets move onto how striped volumes work. But first, lets clean up the linear volume, by unmounting the disk. Okay, so lets just jump back to the diagrams for a minute. Easy enough right, and you will notice this command looks almost exactly the same as the earlier version, just with the added stripes and stripesize options.

These rather simple options dramatically change the performance profile as we will see in a minute. I just wanted to mention that it is not always clear by looking at lvdisplay whether you are running in linear or striped mode.

You can see that the default lvdisplay output does not tell you anything interesting in that regard. You can use lvs segments to give you a little information about the logical volume, but if you are looking for detailed information about the logical volume, try running lvdisplay -vm, as you can see there is a bunch of output, lets just scroll up here. So, we have our default output about the volume up top, then down here, we have detailed info about the stripe size and the devices which back it.

Just as we did last time, lets go ahead and create a filesystem on this device by running, mkfs. Finally, lets verify it is mounted correctly. Just as we did last time, lets configure the bonnie benchmark to run in the first terminal window, and use the second for the disk monitoring software. Lets just quickly hop over to the second window and verify there is no disk activity before running the benchmark command.

Looks good, so lets execute the benchmark and then watch the disk activity. At this point, you can see that all of our SSD disks are getting exercised. While doing research for this episode, it was explained that writes go to the disks in a round-robin fashion, and as you can see, this certainly seems to be the case, and this time around the benchmark completed much more quickly because we are actually using all of the disks.

So, lets just recap with a couple diagrams and some closing notes. Linear volumes, like we saw in the earlier example, write to the disks in series, as one disk fills up, the next fills, and so on.

This is in comparison to how striped logical volumes work. With striped logical volumes, writes head to the disk in a round-robin fashion, so you will actually see much better performance because you are using more disks, and not creating hot spots, or saturating one disk in the array. This is probably a good place to leave this episode, as I think this one slide highlights the entire discussion. However, our results do raise some interesting questions, these are ones that you will likely run into too, if you venture down this path.

Here are the performance numbers between linear and striped logical volumes. As you can see, striped logical volumes absolutely kill linear volume types.

What is interesting, is that I expected to see higher numbers, specifically for sequential reads for the striped volume type. AWS is a bit of a black box, in that if we had physical hardware, we could play around with various typologies to see if we can get better performance. Personally, I think we are saturating some type of link, but this is hard to diagnose without knowing the typology layout, or having access to the physical hardware. The real goal of this episode was to teach the difference between linear and striped logical volumes and I think we have done that so far.

But, if I was to implement this for a project I was working on, there are likely other bits I would want to test and profile.

LVM PE Striping to maximize Hyper-Converged storage throughput |

Red Hat's documentation publication system recently went through an upgrade to enable speedier, more mobile-friendly content.

We decided to re-evaluate our commenting platform to ensure that it meets your expectations and serves as an optimal feedback mechanism.

During this redesign, we invite your input on providing feedback on Red Hat documentation via the discussion platform. Creating Striped Volumes. When you create a striped logical volume, you specify the number of stripes with the -i argument of the lvcreate command. This determines over how many physical volumes the logical volume will be striped.

The number of stripes cannot be greater than the number of physical volumes in the volume group unless the --alloc anywhere argument is used. If the underlying physical devices that make up a striped logical volume are different sizes, the maximum size of the striped volume is determined by the smallest underlying device. For example, in a two-legged stripe, the maximum size is twice the size of the smaller device. In a three-legged stripe, the maximum size is three times the size of the smallest device.

The following command creates a striped logical volume across 2 physical volumes with a stripe of 64kB. The logical volume is 50 gigabytes in size, is named gfslv , and is carved out of volume group vg0. As with linear volumes, you can specify the extents of the physical volume that you are using for the stripe. The following command creates a striped volume extents in size that stripes across two physical volumes, is named stripelv and is in volume group testvg.

Creating Linear Logical Volumes 5. Creating Mirrored Volumes. Where did the comment section go? Here are the common uses of Markdown. Learn more Close.

Lvm striping

Lvm striping