AW: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
Hi, Von: Dirk Heinrichs [mailto:[EMAIL PROTECTED] Hi, since you seem to be german, there's an article about SW-/MoBo-/HW-RAID in the current issue of c't magazine. Thank you, bought the issue - it was rather helpful to me! Ciao, Wolfgang
Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
On Monday 20 October 2008 16:33:24 Volker Armin Hemmann wrote: after a nice person on this list gave me a good tip, I was able to (and I still do) have root on raid1 without initrd/ramfs crap. commandline: root=/dev/md1 md=1,1,/dev/sda3,/dev/sdb3 nopat nmi_watchdog=0 md auto assembling before init kicks in: [...] I don't even need that detail in my command line. (This box has five RAID-1 partitions, composed of identical partitions on identical SATA disks.) Mine just looks like this: kernel /boot/kernel-x86_64-2.6.27-gentoo root=/dev/md0 vga=0x31A video=vesafb:mtrr:3,ywrap fbcon=scrollback:128k splash=silent The md code in the kernel manages to find all the partitions at boot time and stitches them together properly. No problem. -- Rgds Peter
RE: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
On Mon, 20 Oct 2008 13:24:11 +0200 Volker Armin Hemmann [EMAIL PROTECTED] wrote: On Montag 20 Oktober 2008, Conway S. Smith wrote: On Mon, 20 Oct 2008 08:54:20 +0200 Wolfgang Liebich [EMAIL PROTECTED] wrote: Hi, SNIP the howtos on gentoo-wiki worked well for me. I'm working with them, too. Just one question remains: I want to use udev. Do I have to create the md devices or does udev that for me? udev will do it for you. But make sure your initramfs init script unmounts /sys /proc. just don't use an initramfs/initrd. From my reading initramfs/initrd is the preferred way of handling root filesystem on MD RAID - and the only way for metadata 1.[012] (although I'm having trouble finding where I read that only 0.90 works w/ in-kernel detection/assembly). From /usr/share/doc/mdadm-2.6.7/README.initramfs.bz2: The preferred way to assemble md arrays at boot time is using 'mdadm' or 'mdassemble' (which is a trimmed-down mdadm). To assemble an array which contains the root filesystem, mdadm needs to be run before that filesystem is mounted, and so needs to be run from an initial-ram-fs. Conway S. Smith -- The only intuitive interface is the nipple. After that, it's all learned. (Bruce Ediger, [EMAIL PROTECTED], in comp.os.linux.misc, on X interfaces.)
Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
Hi, SNIP the howtos on gentoo-wiki worked well for me. I'm working with them, too. Just one question remains: I want to use udev. Do I have to create the md devices or does udev that for me? - Put the root partition on another RAID1 (I thought about putting the root filesystem into my LVM setup, too -- it is REALLY annoying if the root partition get's to small), yeah, but if you have 20+ gb root is always big enough ;) AFAIK lvm kills barriers. You use raid for better data security. So using lvm is a bit.. contra productive. Sorry, I'm neither a LVM nor a RAID export - could you please elaborate on that? I like LVM because of the convenience it adds. - Build a RAID1 partition for the rest of the system (will be a LVM2 container) - Build a last RAID0 partition for scratch data (/tmp, /var/tmp, /usr/portage, scratch data). I have /tmp and /var/tmp on tmpfs - /tmp is so small it is not worth wasting a partition for it. /tmp --- maybe now (4GB ram). /var/tmp - not sure (OpenOffice compile comes to mind here :-) Ciao, Wolfgang
Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
On Mon, 20 Oct 2008 08:54:20 +0200 Wolfgang Liebich [EMAIL PROTECTED] wrote: Hi, SNIP the howtos on gentoo-wiki worked well for me. I'm working with them, too. Just one question remains: I want to use udev. Do I have to create the md devices or does udev that for me? udev will do it for you. But make sure your initramfs init script unmounts /sys /proc. On the box I'm working on setting up it wasn't unmounting /sys on the initramfs, so when it switched to the real root it thought /sys was already mounted didn't mount /sys under the real root, which meant that udev didn't work - which took me a while to figure out. - Put the root partition on another RAID1 (I thought about putting the root filesystem into my LVM setup, too -- it is REALLY annoying if the root partition get's to small), yeah, but if you have 20+ gb root is always big enough ;) AFAIK lvm kills barriers. You use raid for better data security. So using lvm is a bit.. contra productive. Sorry, I'm neither a LVM nor a RAID export - could you please elaborate on that? I like LVM because of the convenience it adds. Write barriers are a feature to allow write caching on the hard disks w/out endangering filesystem integrity. Write caching helps performance significantly, but also allows the disk to re-order write requests - the disk may actually write a write-request that was received later before a write-request that was received earlier, which in some situations can lead to filesystem corruption. Write barriers are a special type of request that the disk is not allowed to reorder around - everything the disk receives before the write barrier must be written before anything received after the write barrier. But in order to work, write barriers need to be supported by every layer from the filesystem down to the actual disk; if your filesystem is on top of LVM LVM doesn't support write barriers, then you won't be able to use them, and if write caching is enabled on the actual disks, you may be risking fileystem corruption. The Device Mapper kernel subsystem (dm-crypt, dm-raid, LVM, etc.) does not support write barriers - but neither does MD RAID except for RAID1, so write caching is dangerous except for filesystems directly on disk partitions or on RAID1 (if the RAID1 is directly on disk partitions). I personally decided against using LVM because from what I read it's difficult to correctly stripe-align LVM, and incorrect alignment can have a very big performance impact. Good luck, Conway S. Smith -- The only intuitive interface is the nipple. After that, it's all learned. (Bruce Ediger, [EMAIL PROTECTED], in comp.os.linux.misc, on X interfaces.)
Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
On Mon, 20 Oct 2008 13:24:11 +0200 Volker Armin Hemmann [EMAIL PROTECTED] wrote: On Montag 20 Oktober 2008, Conway S. Smith wrote: On Mon, 20 Oct 2008 08:54:20 +0200 Wolfgang Liebich [EMAIL PROTECTED] wrote: Hi, SNIP the howtos on gentoo-wiki worked well for me. I'm working with them, too. Just one question remains: I want to use udev. Do I have to create the md devices or does udev that for me? udev will do it for you. But make sure your initramfs init script unmounts /sys /proc. just don't use an initramfs/initrd. From my reading initramfs/initrd is the preferred way of handling root filesystem on MD RAID - and the only way for metadata 1.[012] (although I'm having trouble finding where I read that only 0.90 works w/ in-kernel detection/assembly). From /usr/share/doc/mdadm-2.6.7/README.initramfs.bz2: The preferred way to assemble md arrays at boot time is using 'mdadm' or 'mdassemble' (which is a trimmed-down mdadm). To assemble an array which contains the root filesystem, mdadm needs to be run before that filesystem is mounted, and so needs to be run from an initial-ram-fs. Conway S. Smith -- The only intuitive interface is the nipple. After that, it's all learned. (Bruce Ediger, [EMAIL PROTECTED], in comp.os.linux.misc, on X interfaces.)
Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
On Montag 20 Oktober 2008, Conway S. Smith wrote: On Mon, 20 Oct 2008 08:54:20 +0200 Wolfgang Liebich [EMAIL PROTECTED] wrote: Hi, SNIP the howtos on gentoo-wiki worked well for me. I'm working with them, too. Just one question remains: I want to use udev. Do I have to create the md devices or does udev that for me? udev will do it for you. But make sure your initramfs init script unmounts /sys /proc. just don't use an initramfs/initrd. Sorry, I'm neither a LVM nor a RAID export - could you please elaborate on that? I like LVM because of the convenience it adds. Write barriers are a feature to allow write caching on the hard disks w/out endangering filesystem integrity. Write caching helps performance significantly, but also allows the disk to re-order write requests - the disk may actually write a write-request that was received later before a write-request that was received earlier, which in some situations can lead to filesystem corruption. Write barriers are a special type of request that the disk is not allowed to reorder around - everything the disk receives before the write barrier must be written before anything received after the write barrier. But in order to work, write barriers need to be supported by every layer from the filesystem down to the actual disk; if your filesystem is on top of LVM LVM doesn't support write barriers, then you won't be able to use them, and if write caching is enabled on the actual disks, you may be risking fileystem corruption. The Device Mapper kernel subsystem (dm-crypt, dm-raid, LVM, etc.) does not support write barriers - but neither does MD RAID except for RAID1, so write caching is dangerous except for filesystems directly on disk partitions or on RAID1 (if the RAID1 is directly on disk partitions). also, reiserfs and xfs turn barriers on by default, ext3 turns it off per default. Because of 'performance reasons'.
Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
On Montag 20 Oktober 2008, Conway S. Smith wrote: On Mon, 20 Oct 2008 13:24:11 +0200 Volker Armin Hemmann [EMAIL PROTECTED] wrote: On Montag 20 Oktober 2008, Conway S. Smith wrote: On Mon, 20 Oct 2008 08:54:20 +0200 Wolfgang Liebich [EMAIL PROTECTED] wrote: Hi, SNIP the howtos on gentoo-wiki worked well for me. I'm working with them, too. Just one question remains: I want to use udev. Do I have to create the md devices or does udev that for me? udev will do it for you. But make sure your initramfs init script unmounts /sys /proc. just don't use an initramfs/initrd. From my reading initramfs/initrd is the preferred way of handling root filesystem on MD RAID - and the only way for metadata 1.[012] (although I'm having trouble finding where I read that only 0.90 works w/ in-kernel detection/assembly). From /usr/share/doc/mdadm-2.6.7/README.initramfs.bz2: The preferred way to assemble md arrays at boot time is using 'mdadm' or 'mdassemble' (which is a trimmed-down mdadm). To assemble an array which contains the root filesystem, mdadm needs to be run before that filesystem is mounted, and so needs to be run from an initial-ram-fs. after a nice person on this list gave me a good tip, I was able to (and I still do) have root on raid1 without initrd/ramfs crap. commandline: root=/dev/md1 md=1,1,/dev/sda3,/dev/sdb3 nopat nmi_watchdog=0 md auto assembling before init kicks in: [4.066796] md: Autodetecting RAID arrays. [4.139083] md: Scanned 8 and added 8 devices. [4.139158] md: autorun ... [4.139232] md: considering sdb6 ... [4.139309] md: adding sdb6 ... [4.139384] md: sdb5 has different UUID to sdb6 [4.139460] md: sdb3 has different UUID to sdb6 [4.139535] md: sdb1 has different UUID to sdb6 [4.139611] md: adding sda6 ... [4.139686] md: sda5 has different UUID to sdb6 [4.139761] md: sda3 has different UUID to sdb6 [4.139837] md: sda1 has different UUID to sdb6 [4.140008] md: created md3 [4.140084] md: bindsda6 [4.140162] md: bindsdb6 [4.140240] md: running: sdb6sda6 [4.140533] raid1: raid set md3 active with 2 out of 2 mirrors [4.140650] md: considering sdb5 ... [4.140726] md: adding sdb5 ... [4.140801] md: sdb3 has different UUID to sdb5 [4.140884] md: sdb1 has different UUID to sdb5 [4.140960] md: adding sda5 ... [4.141034] md: sda3 has different UUID to sdb5 [4.141110] md: sda1 has different UUID to sdb5 [4.141259] md: created md2 [4.141334] md: bindsda5 [4.141413] md: bindsdb5 [4.141491] md: running: sdb5sda5 [4.141757] raid1: raid set md2 active with 2 out of 2 mirrors [4.141872] md: considering sdb3 ... [4.141950] md: adding sdb3 ... [4.142025] md: sdb1 has different UUID to sdb3
Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
On Friday 17 October 2008 12:43:15 Volker Armin Hemmann wrote: I have /tmp and /var/tmp on tmpfs - /tmp is so small it is not worth wasting a partition for it. Yes, and you can enlarge it by creating plenty of swap. My 4GB of real RAM isn't enough to compile the biggest programs, but setting /etc/fstab thus: tmpfs /tmp tmpfs nodev,nosuid,size=6g 0 0 I get enough /tmp space when I need it without have to go out and spend money on more RAM. Neat. -- Rgds Peter
Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
Hi, Alan McKinnon schrieb: On Wednesday 15 October 2008 15:13:45 Pintér Tibor wrote: I'm in the process of setting up a new private computer. I've bought one with two drives b/c I wanted to setup a RAID system - RAID1 for important partitions, RAID0 for scratch files maybe. Additionally I would like to use LVM2 --- on my work PC I've grown to like the flexibility of that. The Intel DQ35JO motherboard now supports some kind of mobo based RAID. Is it better to use this HW raid, or to ignore that and use only the linux kernel's software RAID. thats not hardware raid, it never was, it never will be. Rule of thumb: For any machine you buy to use at home, dump the on-board RAID and use Linux software raid instead. Reason: kernel raid works, that on-board crap doesn't Other reason: real hardware raid costs many times more than that entire computer you bought for home use OK - nearly everyone here (and at work, too) told me to forget the onboard fake raid controller. So this is what I will do :-) The RAID-Howto as well as the LVM howto are however woefully out of date. I will try to work with the linux-raid website's info. Basically I plan to do: - Put the boot partition on a RAID1 - Put the root partition on another RAID1 (I thought about putting the root filesystem into my LVM setup, too -- it is REALLY annoying if the root partition get's to small), but it seems safer to let root be an own partition. Or are there any different opinions here? I'm very interested in hearing experiences... - Build a RAID1 partition for the rest of the system (will be a LVM2 container) - Build a last RAID0 partition for scratch data (/tmp, /var/tmp, /usr/portage, scratch data). Any comments? Obviously insane? :-) Don't think so. - Wolfgang
Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
On Fri, 17 Oct 2008 12:40:52 +0200, Wolfgang Liebich wrote: Basically I plan to do: - Put the boot partition on a RAID1 - Put the root partition on another RAID1 (I thought about putting the root filesystem into my LVM setup, too -- it is REALLY annoying if the root partition get's to small), but it seems safer to let root be an own partition. Or are there any different opinions here? I'm very interested in hearing experiences... I have a small root partition on RAID1 and everything else (except swap) in an LVM group, also on RAID. This avoids the need for a separate /boot. -- Neil Bothwick Isn't 'Criminal Lawyer' rather redundant? signature.asc Description: PGP signature
Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
On Freitag 17 Oktober 2008, Wolfgang Liebich wrote: Hi, Alan McKinnon schrieb: On Wednesday 15 October 2008 15:13:45 Pintér Tibor wrote: I'm in the process of setting up a new private computer. I've bought one with two drives b/c I wanted to setup a RAID system - RAID1 for important partitions, RAID0 for scratch files maybe. Additionally I would like to use LVM2 --- on my work PC I've grown to like the flexibility of that. The Intel DQ35JO motherboard now supports some kind of mobo based RAID. Is it better to use this HW raid, or to ignore that and use only the linux kernel's software RAID. thats not hardware raid, it never was, it never will be. Rule of thumb: For any machine you buy to use at home, dump the on-board RAID and use Linux software raid instead. Reason: kernel raid works, that on-board crap doesn't Other reason: real hardware raid costs many times more than that entire computer you bought for home use OK - nearly everyone here (and at work, too) told me to forget the onboard fake raid controller. So this is what I will do :-) The RAID-Howto as well as the LVM howto are however woefully out of date. I will try to work with the linux-raid website's info. the howtos on gentoo-wiki worked well for me. - Put the root partition on another RAID1 (I thought about putting the root filesystem into my LVM setup, too -- it is REALLY annoying if the root partition get's to small), yeah, but if you have 20+ gb root is always big enough ;) AFAIK lvm kills barriers. You use raid for better data security. So using lvm is a bit.. contra productive. - Build a RAID1 partition for the rest of the system (will be a LVM2 container) - Build a last RAID0 partition for scratch data (/tmp, /var/tmp, /usr/portage, scratch data). I have /tmp and /var/tmp on tmpfs - /tmp is so small it is not worth wasting a partition for it.
Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
Wolfgang Liebich wrote: Hi, OK - nearly everyone here (and at work, too) told me to forget the onboard fake raid controller. So this is what I will do :-) The RAID-Howto as well as the LVM howto are however woefully out of date. I will try to work with the linux-raid website's info. Basically I plan to do: - Put the boot partition on a RAID1 - Put the root partition on another RAID1 (I thought about putting the root filesystem into my LVM setup, too -- it is REALLY annoying if the root partition get's to small), but it seems safer to let root be an own partition. Or are there any different opinions here? I'm very interested in hearing experiences... - Build a RAID1 partition for the rest of the system (will be a LVM2 container) - Build a last RAID0 partition for scratch data (/tmp, /var/tmp, /usr/portage, scratch data). Any comments? Obviously insane? :-) Don't think so. - Wolfgang Likewhoa has a nice writedown of raid and LVM2 on gentoo forums http://forums.gentoo.org/viewtopic-t-702681-highlight-likewhoa+recipe.html?sid=e9df56d90808ed712323ca693936a004. Using that it should be easy enough to adjust to your needs. Greets jormaa
Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
On Wed, Oct 15, 2008 at 8:08 AM, Wolfgang Liebich [EMAIL PROTECTED] wrote: Hi, I'm in the process of setting up a new private computer. I've bought one with two drives b/c I wanted to setup a RAID system - RAID1 for important partitions, RAID0 for scratch files maybe. Additionally I would like to use LVM2 --- on my work PC I've grown to like the flexibility of that. The Intel DQ35JO motherboard now supports some kind of mobo based RAID. Is it better to use this HW raid, or to ignore that and use only the linux kernel's software RAID. Additionally the LVM2 utilities seem to have limited mirroring/striping capabilities of their own - I only want to use RAID levels 0 and 1 anyways -- would LVM's methods be better here? Hi, I've got 4 regular 500gb SATA drives in a linux software RAID5 (BIOS fakeraid disabled), not using LVM, and with a AES dmcrypt on top of it, and the performance is really good in my opinion. The encrypted RAID has a faster read speed than a single, non-RAID, non-encrypted SATA drive of the same model. Obviously with the encryption parity calculations the writes are not as fast, but it's still 25 megabytes per second write speed which seems pretty good to me. I have a Core 2 E6600 (overclocked to 3ghz). The time to rebuild the RAID after a system failure for this 4x500gb is about 90 minutes. Good luck, Paul
Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
I'm in the process of setting up a new private computer. I've bought one with two drives b/c I wanted to setup a RAID system - RAID1 for important partitions, RAID0 for scratch files maybe. Additionally I would like to use LVM2 --- on my work PC I've grown to like the flexibility of that. The Intel DQ35JO motherboard now supports some kind of mobo based RAID. Is it better to use this HW raid, or to ignore that and use only the linux kernel's software RAID. thats not hardware raid, it never was, it never will be. t
Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
If you want to be sure your data is still readable in the event that your mobo dies and you can't find a replacement with the same fake RAID controller, stick with Linux kernel RAID. ...or buy a 3ware/areca/adaptec card, which is 100% supported. (but those are heavy bucks) t
[gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
Hi, I'm in the process of setting up a new private computer. I've bought one with two drives b/c I wanted to setup a RAID system - RAID1 for important partitions, RAID0 for scratch files maybe. Additionally I would like to use LVM2 --- on my work PC I've grown to like the flexibility of that. The Intel DQ35JO motherboard now supports some kind of mobo based RAID. Is it better to use this HW raid, or to ignore that and use only the linux kernel's software RAID. Additionally the LVM2 utilities seem to have limited mirroring/striping capabilities of their own - I only want to use RAID levels 0 and 1 anyways -- would LVM's methods be better here? Inquiring mind wants to know! - Wolfgang Liebich
Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
Hi guys, I've had some experience in the past with software (BIOS) RAID. Obviously there would be a big performance difference with hardware vs BIOS RAID. Has anyone done any benchmarks to the effect of BIOS vs linux kernel RAID? Thanks, D Wolfgang Liebich wrote: Hi, I'm in the process of setting up a new private computer. I've bought one with two drives b/c I wanted to setup a RAID system - RAID1 for important partitions, RAID0 for scratch files maybe. Additionally I would like to use LVM2 --- on my work PC I've grown to like the flexibility of that. The Intel DQ35JO motherboard now supports some kind of mobo based RAID. Is it better to use this HW raid, or to ignore that and use only the linux kernel's software RAID. Additionally the LVM2 utilities seem to have limited mirroring/striping capabilities of their own - I only want to use RAID levels 0 and 1 anyways -- would LVM's methods be better here? Inquiring mind wants to know! - Wolfgang Liebich signature.asc Description: OpenPGP digital signature
Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
Hi, since you seem to be german, there's an article about SW-/MoBo-/HW-RAID in the current issue of c't magazine. Bye... Dirk -- Dirk Heinrichs | Tel: +49 (0)162 234 3408 Configuration Manager | Fax: +49 (0)211 47068 111 Capgemini Deutschland | Mail: [EMAIL PROTECTED] Wanheimerstraße 68 | Web: http://www.capgemini.com D-40468 Düsseldorf | ICQ#: 110037733 GPG Public Key C2E467BB | Keyserver: wwwkeys.pgp.net signature.asc Description: This is a digitally signed message part.
Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
Your mobo RAID is most likely software/BIOS RAID (what some people call fake RAID). The point is it's software that's doing the real work. If you want to be sure your data is still readable in the event that your mobo dies and you can't find a replacement with the same fake RAID controller, stick with Linux kernel RAID.
Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
On Mittwoch 15 Oktober 2008, Dan Cowsill wrote: Hi guys, I've had some experience in the past with software (BIOS) RAID. Obviously there would be a big performance difference with hardware vs BIOS RAID. Has anyone done any benchmarks to the effect of BIOS vs linux kernel RAID? yes. google for it. linux software always wins. Faster, more flexible.
Re: [gentoo-user] Is an Intel motherboard RAID better or worse than software RAID?
On Wednesday 15 October 2008 15:13:45 Pintér Tibor wrote: I'm in the process of setting up a new private computer. I've bought one with two drives b/c I wanted to setup a RAID system - RAID1 for important partitions, RAID0 for scratch files maybe. Additionally I would like to use LVM2 --- on my work PC I've grown to like the flexibility of that. The Intel DQ35JO motherboard now supports some kind of mobo based RAID. Is it better to use this HW raid, or to ignore that and use only the linux kernel's software RAID. thats not hardware raid, it never was, it never will be. Rule of thumb: For any machine you buy to use at home, dump the on-board RAID and use Linux software raid instead. Reason: kernel raid works, that on-board crap doesn't Other reason: real hardware raid costs many times more than that entire computer you bought for home use -- alan dot mckinnon at gmail dot com
