phaq

Last week we had a discussion at the office wether it would possible to span a RAID across USB sticks.
That question came up as a joke while I was working on some RAID system for evaluation purposes.
Well, my friend doubted it when I replied that it would definitely work out with a FreeBSD software RAID using gmirror (geom vinum as a matter of fact works, too).

Proof?
Read more…

Back some time I announced reviewing FreeBSD’s geom software RAID implementations.

Todays article compares geom stripe (gstripe) along with geom gvinum (gvinum) for disk striping (RAID0).

All testing was done on the same hardware as before to get results comparable to previous tests.

Benchmarks were taken using stripe sizes of 64k, 128k and 256k and measured using dd, bonnie++ and rawio as before.

As for the technology gstripe follows the same approach than gmirror which I look at previously.

# rawio benchmark results

rawio was choosen to measure I/O speed during concurrent access. rawio was set to run all tests (random read, seq read, random write, seq write) with eight processes on the /dev/stripe/* and /dev/gvinum/* devices.

Results for the single disk are provided as well to compare performance not only between the different frameworks but also against the native disk performance.

Click the images to see the actual result values and a chart.

529

532

# dd benchmark results

dd was choosen to measure raw block access to /dev/mirror/* and /dev/gvinum/* devices. dd was set to run sequential read and write tests using block sizes from 16k to 1024k.

Click the images to see the actual result values and a chart.

523

520

# bonnie++ benchmark results

finally, bonnie++ was used get pure file system performance.

Click the images to see the actual result values and a chart.

517

513

# conclusion

Looking at raw disk access I must conclude that none of the frameworks beats single disk performance in overall when it comes to blockwise input/output with dd.
gvinum generally performs better than gstripe except when using 256k stripe sizes.

Now since ‘dd’ is very synthetic by it’s nature, rawio is much better to see how the devices would perform under a more “real-life” situation.
Although rawio benchmark results may look low, these numbers where achieved by running 8 processes at once. They’ll reflect best what could be expected in a true multi-user environment with concurrent access.
As from the results there is no absolute winner, as depending on the stripe sizes either of both implementations out-performs the other.

Finally for bonnie++ we see some interesting results. Performance is almost identical for all implementations.
One notable exception was seen with gvinum (64k stripe size) which clearly outperformed its competitors..
One must keep in mind that the first six tests performed by bonnie++ (rand delete/read/create, seq delete/read/create) are limited by I/O performance of both the system bus and the device itself. The hardware I used for testing was capable of about 160 – 170 I/Os per second. I admit that results could be different if the tests are re-run on decent hardware with a higher I/O throughput. It’s possible that modern hardware reveals an I/O barrier for abstracted devices which cannot be seen from my tests.

Personally I prefer using gstripe over gvinum because of it’s more simplistic configuration approach. In terms of performance, gvinum seems to offer superiour performance when it comes to disk striping.

The next article will discuss gvinum and gstripe for RAID10.

This article should have been published already last month, unfortunately the draft was left forgotten for a while in my mailbox.

As some may remember I published two articles on how to setup GEOM disk mirroring on alpha and sparc earlier this year. These articles were originally based upon Ralf Engelschalls disk mirroring howto.

I had installed GEOM disk mirrors on various occasions since then, though I always felt that converting to a GEOM mirror like that involved too much work.

So I went on to find a better and faster way to achieve the task and I found one.
Read more…

This article describes a concept on how to implement realtime file system replication on a dual-node FreeBSD cluster to provide real HA services.
Maybe you are familiar with DRBD (distributed replicated block device) from the Linux world already, which basically does something we could call network-RAID1.
Read more…

Yet another software RAID howto, I seem to be growing these in a hurry after all 😉

This time I will cover NetBSD’s RaidFrame and how to setup RAID1 disk mirroring on a Digital Alpha PWS433au.
Read more…

Not long ago a friend of mine generously donated me a Sun E450 server for use with my current networking projects.

The machine came along with four IBM DDRS34560 hard drives. Since a capacity of 4 GB per drive is not that overwhelming by today’s standards I was looking forward to incorporate them into a RAID5 array.
Read more…

After my recent article about FreeBSD GEOM mirroring on Sparc64 I was asked how to boot from a degraded array if the primary hard disk had failed.
The point was how to prevent the admin to interact with OpenBoot in that case.
I’m sure this will only apply to people not very familiar with Sun’s OpenBoot, as most other people will surely know about this.
Read more…

Actually my experience in GEOM disk mirroring on Alpha dates back to FreeBSD 5.3, though it seems to work out perfectly after upgrading to FreeBSD 6.0.

Again, the concept is similar to setting up a mirror on intel boxes, though – again – there are some minor differences which may cause some headaches!
Read more…

As I promised earlier I will have a look at setting up a GEOM mirror on Sparc64 using FreeBSD 6.

Though it is quiet similar to the Intel world, there are some minor differences which I’m going to show you.
Read more…

It was already the 5.x branch of FreeBSD which included the GEOM driver for creating RAID arrays of any kind.

As Ralf S. Engelschall pointed out in his famous howto, GEOM was eventually to replace ATA, CCD and good old vinum.

It may not always make sense to put a full-featured RAID controller into a box when it serves only some “minor” purpose or performance is not an issue (costs may also be a consideration), so a software RAID solution may sometimes be good enough.
Read more…