Software raid OK?
Hi List! I installed a software raid, level1 with 3 disks, one of them is a spare. I have 2 partitions: md0 is for / and is made of sda1,sdb1, sdc1 md1 is for swap and made of sda2,sdb2, sdc2 - I can boot form both disks, - the system works fine. - mdstat says the raids are active - mdmadm --detail seems to be fine ( Superblock is persistent ) However mdadm -E says: no md superblock detected on /dev/md0 and fdisk -l says: no valid partition table found on md0 Is the raid OK or not? If not, how can I fix it? THX Akos -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org
Re: Software raid OK?
Le Monday 20 April 2009 11:44:31 BAGI Akos, vous avez écrit : Hi List! I installed a software raid, level1 with 3 disks, one of them is a spare. I have 2 partitions: md0 is for / and is made of sda1,sdb1, sdc1 md1 is for swap and made of sda2,sdb2, sdc2 - I can boot form both disks, - the system works fine. - mdstat says the raids are active - mdmadm --detail seems to be fine ( Superblock is persistent ) However mdadm -E says: no md superblock detected on /dev/md0 mdadm -E handles RAID components, not the resulting RAID device. You can have informations with mdadm -E /dev/sda1 for example. To see the state of your RAID device, you can do : $ cat /proc/mdstat or $ mdadm --details /dev/md0 and fdisk -l says: no valid partition table found on md0 fdisk handles disks, not partitions. md0 = RAID of sda1,sdb1,sdc1 partitions = a partition, with a filesystem on it. Is the raid OK or not? If not, how can I fix it? No problem with your raid. signature.asc Description: This is a digitally signed message part.
Re: Software raid OK?
When the date was Monday 20 April 2009, BAGI Akos wrote: Hi List! I installed a software raid, level1 with 3 disks, one of them is a spare. I have 2 partitions: md0 is for / and is made of sda1,sdb1, sdc1 md1 is for swap and made of sda2,sdb2, sdc2 There is no particularly good reason to have the swap on RAID. You should define three independed swap partitions; if disk fails, kernel will use the other available. -- Michael Iatrou -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org
Re: Software raid OK?
On Mon, Apr 20, 2009 at 03:29:00PM +0300, Michael Iatrou wrote: When the date was Monday 20 April 2009, BAGI Akos wrote: Hi List! I installed a software raid, level1 with 3 disks, one of them is a spare. I have 2 partitions: md0 is for / and is made of sda1,sdb1, sdc1 md1 is for swap and made of sda2,sdb2, sdc2 There is no particularly good reason to have the swap on RAID. You should define three independed swap partitions; if disk fails, kernel will use the other available. If swap fails, what happens if something important to the running of the system (not just a user app) is swapped-out? I've seen advice on this list many times that to avoid a crash, if other system stuff is on raid, that swap should be as well. Doug. -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org
Re: Software raid OK?
When the date was Monday 20 April 2009, Douglas A. Tutty wrote: On Mon, Apr 20, 2009 at 03:29:00PM +0300, Michael Iatrou wrote: When the date was Monday 20 April 2009, BAGI Akos wrote: Hi List! I installed a software raid, level1 with 3 disks, one of them is a spare. I have 2 partitions: md0 is for / and is made of sda1,sdb1, sdc1 md1 is for swap and made of sda2,sdb2, sdc2 There is no particularly good reason to have the swap on RAID. You should define three independed swap partitions; if disk fails, kernel will use the other available. If swap fails, what happens if something important to the running of the system (not just a user app) is swapped-out? I've seen advice on this list many times that to avoid a crash, if other system stuff is on raid, that swap should be as well. I cannot confirm that; instead I am assuming a workflow like the following: 1. A disk is about to fail 2. Notification from SMART hits sysadmin's mailbox 3. # swapoff /dev/sdXY 4. Replace disk, create partitions 5. # swapon /dev/sdXY 6. # mdadm /dev/mdK -a /dev/sdXZ -- Michael Iatrou -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org
Re: Software raid OK?
Michael, 2009/4/20 Michael Iatrou m.iat...@freemail.gr When the date was Monday 20 April 2009, Douglas A. Tutty wrote: On Mon, Apr 20, 2009 at 03:29:00PM +0300, Michael Iatrou wrote: There is no particularly good reason to have the swap on RAID. You should define three independed swap partitions; if disk fails, kernel will use the other available. If swap fails, what happens if something important to the running of the system (not just a user app) is swapped-out? I've seen advice on this list many times that to avoid a crash, if other system stuff is on raid, that swap should be as well. I cannot confirm that; instead I am assuming a workflow like the following: 1. A disk is about to fail 2. Notification from SMART hits sysadmin's mailbox 3. # swapoff /dev/sdXY 4. Replace disk, create partitions 5. # swapon /dev/sdXY 6. # mdadm /dev/mdK -a /dev/sdXZ If the system is running unattended - for instance if it's a server being run by a hobbyist, which doesn't have a sysadmin permanently available to respond to problems - then step 3 may not occur before the disk fails. In this scenario, isn't Douglas right that it's better to have the swap on (redundant) RAID? Many thanks, Sam
Re: Software raid OK?
Michael Iatrou wrote: When the date was Monday 20 April 2009, Douglas A. Tutty wrote: On Mon, Apr 20, 2009 at 03:29:00PM +0300, Michael Iatrou wrote: When the date was Monday 20 April 2009, BAGI Akos wrote: Hi List! I installed a software raid, level1 with 3 disks, one of them is a spare. I have 2 partitions: md0 is for / and is made of sda1,sdb1, sdc1 md1 is for swap and made of sda2,sdb2, sdc2 There is no particularly good reason to have the swap on RAID. You should define three independed swap partitions; if disk fails, kernel will use the other available. If swap fails, what happens if something important to the running of the system (not just a user app) is swapped-out? I've seen advice on this list many times that to avoid a crash, if other system stuff is on raid, that swap should be as well. I cannot confirm that; instead I am assuming a workflow like the following: 1. A disk is about to fail 2. Notification from SMART hits sysadmin's mailbox 3. # swapoff /dev/sdXY 4. Replace disk, create partitions 5. # swapon /dev/sdXY 6. # mdadm /dev/mdK -a /dev/sdXZ Relying on S.M.A.R.T. is playing with atomic bombs. Put everything on redundant storage, even swap. Mark Allums -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org
Re: Software raid OK?
When the date was Monday 20 April 2009, Sam Kuper wrote: Michael, 2009/4/20 Michael Iatrou m.iat...@freemail.gr When the date was Monday 20 April 2009, Douglas A. Tutty wrote: On Mon, Apr 20, 2009 at 03:29:00PM +0300, Michael Iatrou wrote: There is no particularly good reason to have the swap on RAID. You should define three independed swap partitions; if disk fails, kernel will use the other available. If swap fails, what happens if something important to the running of the system (not just a user app) is swapped-out? I've seen advice on this list many times that to avoid a crash, if other system stuff is on raid, that swap should be as well. I cannot confirm that; instead I am assuming a workflow like the following: 1. A disk is about to fail 2. Notification from SMART hits sysadmin's mailbox 3. # swapoff /dev/sdXY 4. Replace disk, create partitions 5. # swapon /dev/sdXY 6. # mdadm /dev/mdK -a /dev/sdXZ If the system is running unattended - for instance if it's a server being run by a hobbyist, which doesn't have a sysadmin permanently available to respond to problems - then step 3 may not occur before the disk fails. In this scenario, isn't Douglas right that it's better to have the swap on (redundant) RAID? I don't think there is a silver bullet for this. There is a performance penalty related to soft-RAID. Also swappiness configuration must be taken into account. Physical memory and memory usage patterns from application perspective count too. And of course the required availability for the application is an important factor. All I am saying is that when thorough evaluation of parameters like the above is out of scope, there is probably no good reason to have swap on RAID. -- Michael Iatrou -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org
Re: Software raid OK?
On Mon, Apr 20, 2009 at 10:08:22PM +0300, Michael Iatrou wrote: When the date was Monday 20 April 2009, Sam Kuper wrote: Michael, [snip] I don't think there is a silver bullet for this. There is a performance penalty related to soft-RAID. Also swappiness configuration must be taken into account. Physical memory and memory usage patterns from application perspective count too. And of course the required availability for the application is an important factor. All I am saying is that when thorough evaluation of parameters like the above is out of scope, there is probably no good reason to have swap on RAID. with the cost of hd's being so low, I would suggest the default should be swap on a raid1 -- Microsoft is not the answer. Microsoft is the question. NO (or Linux) is the answer. (Taken from a .signature from someone from the UK, source unknown) signature.asc Description: Digital signature
Re: Software raid OK?
2009/4/21 Alex Samad a...@samad.com.au On Mon, Apr 20, 2009 at 10:08:22PM +0300, Michael Iatrou wrote: When the date was Monday 20 April 2009, Sam Kuper wrote: Michael, [snip] I don't think there is a silver bullet for this. There is a performance penalty related to soft-RAID. Also swappiness configuration must be taken into account. Physical memory and memory usage patterns from application perspective count too. And of course the required availability for the application is an important factor. All I am saying is that when thorough evaluation of parameters like the above is out of scope, there is probably no good reason to have swap on RAID. with the cost of hd's being so low, I would suggest the default should be swap on a raid1 I'm grateful to Mark, Michael and Alex for their replies. I'm planning to go ahead with using RAID 1 for swap, as a possible slight performance hit is more acceptable to me than a crash or data loss would be. Indeed, that's why I'm using redundant RAID in the first place. Apologies for hijacking Bagi's thread! Best, Sam -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org
Re: Software raid OK?
2009/4/21 Sam Kuper sam.ku...@uclmail.net: Apologies for hijacking Bagi's thread! s/Bagi/Akos/ -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org
