Raid: software or hardware
in [Linux Hardware]
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From: vertigo on 11 Jun 2008 01:49 Hello I have mainboard: gigabyte P965S3. I have 2 SATA interfaces using builtin Jmicron controller (and another 4 SATA interfaces) I upgraded bios to version F12. I want to make mirror raid. What's better to use: software or hardware(jmicron)? 1. Using hardware, jmicron (creating raid from bios). Will gentoo see it ? Is it stable ? If one disk fails how will i know ? Will there be no problem with replacing bad disk with new one ? 2. Software raid (using mdadm) What's better ? Has anybody used this jmicron raid ? thanx
From: Aragorn on 11 Jun 2008 05:33 On Wednesday 11 June 2008 07:49, *vertigo* wrote in /comp.os.linux.hardware:/ > Hello > > I have mainboard: gigabyte P965S3. > I have 2 SATA interfaces using builtin Jmicron controller > (and another 4 SATA interfaces) > I upgraded bios to version F12. > I want to make mirror raid. > > What's better to use: software or hardware(jmicron)? Hardware RAID is always preferable over software RAID *if* it is available. However, I sincerely doubt that the onboard SATA RAID of your motherboard will be a hardware RAID. Most likely, it'll be a hardware-assisted software RAID, or if you will, a "WinRAID", just like a Winmodem isn't a real modem. > 1. Using hardware, jmicron (creating raid from bios). > Will gentoo see it ? Is it stable ? I do not know the JMicron, but true hardware SATA RAID from a chip on the motherboard is extremely rare and would also make the board more expensive than its peers. Even if you enable the RAID functionality of an SATA onboard hardware-assisted software RAID, this will only be seen as a RAID by Windows, and then will require you to load the appropriate driver for it, if Windows doesn't have a driver for it by itself. In GNU/Linux, such a device is seen as a simple SATA controller, regardless of whether the RAID functionality is enabled or not, because basically that's what it is. > If one disk fails how will i know ? Both true hardware RAID and software RAID would report this via /syslogd,/ or possibly via an additional daemon like Adaptec's Storage Manager for Adaptec RAID adapters. > Will there be no problem with replacing bad disk with new one ? The replacement of a failed drive in a RAID array is always subject to certain delays and restrictions. Not all RAID adapters (or hard disks!) support hotplugging. When a drive has been replaced, most hardware RAID adapters will automatically rebuild the array - which takes some time and will slow down the machine's performance somewhat - but in software RAID, I believe you have to rebuild the array manually using /mdadm./ -- *Aragorn* (registered GNU/Linux user #223157)
From: vertigo on 11 Jun 2008 06:16 > >> Hello >> >> I have mainboard: gigabyte P965S3. >> I have 2 SATA interfaces using builtin Jmicron controller >> (and another 4 SATA interfaces) >> I upgraded bios to version F12. >> I want to make mirror raid. >> >> What's better to use: software or hardware(jmicron)? > > Hardware RAID is always preferable over software RAID *if* it is > available. > However, I sincerely doubt that the onboard SATA RAID of your motherboard > will be a hardware RAID. > > Most likely, it'll be a hardware-assisted software RAID, or if you will, > a > "WinRAID", just like a Winmodem isn't a real modem. > >> 1. Using hardware, jmicron (creating raid from bios). >> Will gentoo see it ? Is it stable ? > > I do not know the JMicron, but true hardware SATA RAID from a chip on the > motherboard is extremely rare and would also make the board more > expensive > than its peers. > > Even if you enable the RAID functionality of an SATA onboard > hardware-assisted software RAID, this will only be seen as a RAID by > Windows, and then will require you to load the appropriate driver for it, > if Windows doesn't have a driver for it by itself. > > In GNU/Linux, such a device is seen as a simple SATA controller, > regardless > of whether the RAID functionality is enabled or not, because basically > that's what it is. > >> If one disk fails how will i know ? > > Both true hardware RAID and software RAID would report this via > /syslogd,/ > or possibly via an additional daemon like Adaptec's Storage Manager for > Adaptec RAID adapters. > >> Will there be no problem with replacing bad disk with new one ? > > The replacement of a failed drive in a RAID array is always subject to > certain delays and restrictions. Not all RAID adapters (or hard disks!) > support hotplugging. > > When a drive has been replaced, most hardware RAID adapters will > automatically rebuild the array - which takes some time and will slow > down > the machine's performance somewhat - but in software RAID, I believe you > have to rebuild the array manually using /mdadm./ > thanx for this info. That's true - jmicron is not real hardware RAID. Linux kernel has drivers for jmicron software/hardware RAID. So - what is better ? 1. fully software RAID based on mdadm tool 2. or software/hardware jmicron RAID ? What would you suggest ? What is faster ? What makes CPU works less ? Which solution is more reliable ? Thanx
From: Aragorn on 11 Jun 2008 06:35 On Wednesday 11 June 2008 12:16, *vertigo* wrote in /comp.os.linux.hardware:/ >>> [...] >>> 1. Using hardware, jmicron (creating raid from bios). >>> Will gentoo see it ? Is it stable ? >> >> I do not know the JMicron, but true hardware SATA RAID from a chip on the >> motherboard is extremely rare and would also make the board more >> expensive than its peers. >> >> Even if you enable the RAID functionality of an SATA onboard >> hardware-assisted software RAID, this will only be seen as a RAID by >> Windows, and then will require you to load the appropriate driver for it, >> if Windows doesn't have a driver for it by itself. >> >> In GNU/Linux, such a device is seen as a simple SATA controller, >> regardless of whether the RAID functionality is enabled or not, because >> basically that's what it is. >> >> [...] > > thanx for this info. That's true - jmicron is not real hardware RAID. > Linux kernel has drivers for jmicron software/hardware RAID. > > So - what is better ? > 1. fully software RAID based on mdadm tool > 2. or software/hardware jmicron RAID ? In this particular case, there wouldn't be much of a difference performancewise. However, if the Linux kernel has a driver for this chip, then it might be wise to use it, just in the event that using the chipset with the proper driver provides extra functionality - e.g. with regard to error or status reporting - over the default software RAID mechanisms in the rather "universal" Linux software RAID. > What would you suggest ? Try using the /jmicron/ driver and see what gives. If stability issues were to ensue from this driver, then you know you have a safe fallback solution using traditional Linux software RAID. > What is faster ? What makes CPU works less ? There would normally not be any difference in performance or CPU load between a complete software RAID and a hardware-assisted software RAID. They both use the mechanism of software RAID, but the "native" driver might add some functionality. > Which solution is more reliable ? Well, I have no experience with or reports on the /jmicron/ driver, but what I do know is that Linux software RAID is a timeproven and robust solution. If however the /jmicron/ driver is part of the stock Linux kernel tree, then it means that the driver is released under the GPL, and if so, it'll be quite reliable as well, because Linus would never sanction the inclusion of an unstable driver in his stable kernel tree. Just as an illustration (and for what it's worth), a survey conducted by an American university - I forgot which one - a few years ago showed that if one compares two equal amounts of proprietary and FOSS code - i.e. an equal number of lines of code - then the proprietary code contains about 300% to 400% as many bugs as the comparable amount of FOSS code. So in other words, if the driver is included in the stock Linux kernel, then it should statistically be considered about 300 to 400 times more stable than a proprietary driver, even if that proprietary driver were released from the hardware manufacturers themselves - cfr. nVidia and the likes. Bottom line: If this /jmicron/ driver is indeed part of the stock kernel - I keep repeating this because in all honesty I don't know whether it is; I myself tend to favor SCSI solutions instead for RAID and I'm therefore less interested in the PATA/SATA RAID stuff - then the reliability of this driver /should/ be on par with the generic Linux software RAID mechanisms. Basically, the only difference between regular software RAID and the /jmicron/ driver would be the driver for the chipset. In the former case, you would be using a generic SATA driver, and in the latter a driver that appeals to the extra functionality in this chip. Hope this was helpful... ;-) -- *Aragorn* (registered GNU/Linux user #223157)
From: Anton Ertl on 11 Jun 2008 15:01
vertigo <teknet7(a)poczta.onet.pl> writes: >What's better to use: software or hardware(jmicron)? > >1. Using hardware, jmicron (creating raid from bios). >Will gentoo see it ? Is it stable ? >If one disk fails how will i know ? >Will there be no problem with replacing bad disk with new one ? > >2. Software raid (using mdadm) > >What's better ? Has anybody used this jmicron raid ? "Hardware" RAID has the following disadvantages: - When the controller dies, you to install the same hardware to get at your data. At that time, you will probably not be able to buy it anymore, so better buy it now. If you do RAID1, then you may be able to get to the data without additional hardware (but better try that first to be sure), but then you won't have a performance advantage over md even if the jmicron RAID is really hardware RAID. - "Hardware" RAID works on whole disks, md can be applied to partitions; so with md you can RAID1 your valuable data, RAID0 some scratch stuff, and have non-RAID swap partitions. In conclusion, I recommend using md unless you have really good reasons to use something else. BTW, I just wasted a day playing around with an ICH9R-based RAID; the idea was to use the ICH9R RAID1 on Windows and md on Linux, but it does not work that way: contrary to what some people have claimed, Intel's Matrix-RAID does not work on partitions, but allows to divide the disks into two (not more) parts in a different way; the idea is probably that you use RAID1 for one part and RAID0 for the other part. Anyway, I finally gave up on that idea, so Windows just has to do without RAID; it's not so important anyway:-). The aftereffects of my experiments with the RAID cost me another half-day (even after changing the mode to AHCI and writing over the start of the disk, the Windows driver still saw the RAID I had created during the experiments. One other thing worth noting: For md, make sure you create RAIDs with a version 0.90 superblock (mdadm option -e 0.90), because lilo (if you boot from RAID) and kernels as recent as 2.6.19 don't grok the newer superblock formats; even though the documentation says that 0.90 is the default, the Knoppix (5.3 IIRC) mdadm created 1.0 superblocks for me by default:-(. - anton -- M. Anton Ertl Some things have to be seen to be believed anton(a)mips.complang.tuwien.ac.at Most things have to be believed to be seen http://www.complang.tuwien.ac.at/anton/home.html |