Re: SWAP file on a RAID-10 array possible?
Tomas France wrote: This wouldn't be probably the best solution in my situation. The computer we are talking about will be quad-core web server with 8GB RAM and initially 2x500GB SATA HDDs setup in a RAID-1 array. When it begins running low on space or more HDDs performance is needed, I plan to convert the RAID-1 to RAID-10 by adding 2-4 more hard disks (I've found some info on how to do this so hopefully it will work). If I should follow the commonly accepted strategy saying that the swap space should be 2X+ the amount of RAM, that means 16GB. If I add 4 more HDDs in RAID-1 pairs later, then I would end up with 3 swap partitions on RAID-1 taking 96GB (6*16GB) of space on the harddrives which would be a considerable waste of space. Sure, when adding the more hard disks I could probably create a smaller swap partition on each of them but that would be yet another complication. Using a swap file initally on the RAID-1 array and then on the RAID-10 array sounds like a much simpler solution to me as it will allow me to change the size of the swap space more flexibly. After you go to 3-4 drives, most systems don't swap enough to justify the effort of spreading the swap over more drives. Three drives and RAID-10 work well, surely you can use the space on the other drives for another useful purpose. Or just use it, RAID-10 should handle similar partition sizes IIRC. -- bill davidsen [EMAIL PROTECTED] CTO TMR Associates, Inc Doing interesting things with small computers since 1979 - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: SWAP file on a RAID-10 array possible?
This wouldn't be probably the best solution in my situation. The computer we are talking about will be quad-core web server with 8GB RAM and initially 2x500GB SATA HDDs setup in a RAID-1 array. When it begins running low on space or more HDDs performance is needed, I plan to convert the RAID-1 to RAID-10 by adding 2-4 more hard disks (I've found some info on how to do this so hopefully it will work). If I should follow the commonly accepted strategy saying that the swap space should be 2X+ the amount of RAM, that means 16GB. If I add 4 more HDDs in RAID-1 pairs later, then I would end up with 3 swap partitions on RAID-1 taking 96GB (6*16GB) of space on the harddrives which would be a considerable waste of space. Sure, when adding the more hard disks I could probably create a smaller swap partition on each of them but that would be yet another complication. Using a swap file initally on the RAID-1 array and then on the RAID-10 array sounds like a much simpler solution to me as it will allow me to change the size of the swap space more flexibly. Tomas - Original Message - From: Michael Tokarev [EMAIL PROTECTED] To: Tomas France [EMAIL PROTECTED] Cc: linux-raid@vger.kernel.org Sent: Wednesday, August 15, 2007 11:42 PM Subject: Re: SWAP file on a RAID-10 array possible? Tomas France wrote: Thanks for the answer, David! I kind of think RAID-10 is a very good choice for a swap file. For now I will need to setup the swap file on a simple RAID-1 array anyway, I just need to be prepared when it's time to add more disks and transform the whole thing into RAID-10... which will be big fun anyway, for sure ;) By the way, you don't really need raid10 for swap. Built-in linux swap code can utilize multiple swap areas just fine - mkswap + swapon on multiple devices/files. This is essentially a raid0. For raid10, one thing needed is the mirroring, with is provided by raid1. So when you've two drives, use single partition on both to form a raid1 array for swap space. If you've 4 drives, create 2 raid1 arrays and specify them both as swap space, giving them appropriate priority (prio=xxx in swap line in fstab). With 6 drives, have 3 raid1 arrays and so on... This way, the whole thing is much simpler and more manageable. /mjt - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
SWAP file on a RAID-10 array possible?
Hi everyone, I apologize for asking such a fundamental question on the Linux-RAID list but the answers I found elsewhere have been contradicting one another. So, is it possible to have a swap file on a RAID-10 array? Thanks! Tomas - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: SWAP file on a RAID-10 array possible?
Tomas France wrote: Hi everyone, I apologize for asking such a fundamental question on the Linux-RAID list but the answers I found elsewhere have been contradicting one another. So, is it possible to have a swap file on a RAID-10 array? yes. mkswap /dev/mdX swapon /dev/mdX Should you use RAID-10 for swap? That's philosophy :) David - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: SWAP file on a RAID-10 array possible?
Thanks for the answer, David! I kind of think RAID-10 is a very good choice for a swap file. For now I will need to setup the swap file on a simple RAID-1 array anyway, I just need to be prepared when it's time to add more disks and transform the whole thing into RAID-10... which will be big fun anyway, for sure ;) By the way, does anyone know if there is a comprehensive how-to on software RAID with mdadm available somewhere? I mean a website where I could get answers to questions like How to convert your system from no RAID to RAID-1, from RAID-1 to RAID-5/10, how to setup LILO/GRUB to boot from a RAID-1 array etc. Don't take me wrong, I have done my homework and found a lot of info on the topic but a lot of it is several years old and many things have changed since then. And it's quite scattered too.. Tomas - Original Message - From: David Greaves [EMAIL PROTECTED] To: Tomas France [EMAIL PROTECTED] Cc: linux-raid@vger.kernel.org Sent: Wednesday, August 15, 2007 12:10 PM Subject: Re: SWAP file on a RAID-10 array possible? Tomas France wrote: Hi everyone, I apologize for asking such a fundamental question on the Linux-RAID list but the answers I found elsewhere have been contradicting one another. So, is it possible to have a swap file on a RAID-10 array? yes. mkswap /dev/mdX swapon /dev/mdX Should you use RAID-10 for swap? That's philosophy :) David - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: SWAP file on a RAID-10 array possible?
Tomas France wrote: Thanks for the answer, David! you're welome By the way, does anyone know if there is a comprehensive how-to on software RAID with mdadm available somewhere? I mean a website where I could get answers to questions like How to convert your system from no RAID to RAID-1, from RAID-1 to RAID-5/10, how to setup LILO/GRUB to boot from a RAID-1 array etc. Don't take me wrong, I have done my homework and found a lot of info on the topic but a lot of it is several years old and many things have changed since then. And it's quite scattered too.. Yes, I got to thinking that. About a year ago I got a copy of the old raid FAQ from the authors and have started to modify it when I have time and it bubbles up my list. Try http://linux-raid.osdl.org/ It's a community wiki - welcome to the community :) Please feel free to edit,,, Also feel free to post questions/suggestions here if you're not sure. David - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: SWAP file on a RAID-10 array possible?
I used this site to bring my existing Linux install to a RAID 1. It worked great for me. http://wiki.clug.org.za/wiki/RAID-1_in_a_hurry_with_grub_and_mdadm - Original Message - From: [EMAIL PROTECTED] on behalf of Tomas France Sent: Wed, 8/15/2007 5:28am To: linux-raid@vger.kernel.org Subject: Re: SWAP file on a RAID-10 array possible? Thanks for the answer, David! I kind of think RAID-10 is a very good choice for a swap file. For now I will need to setup the swap file on a simple RAID-1 array anyway, I just need to be prepared when it's time to add more disks and transform the whole thing into RAID-10... which will be big fun anyway, for sure ;) By the way, does anyone know if there is a comprehensive how-to on software RAID with mdadm available somewhere? I mean a website where I could get answers to questions like How to convert your system from no RAID to RAID-1, from RAID-1 to RAID-5/10, how to setup LILO/GRUB to boot from a RAID-1 array etc. Don't take me wrong, I have done my homework and found a lot of info on the topic but a lot of it is several years old and many things have changed since then. And it's quite scattered too.. Tomas - Original Message - From: David Greaves [EMAIL PROTECTED] To: Tomas France [EMAIL PROTECTED] Cc: linux-raid@vger.kernel.org Sent: Wednesday, August 15, 2007 12:10 PM Subject: Re: SWAP file on a RAID-10 array possible? Tomas France wrote: Hi everyone, I apologize for asking such a fundamental question on the Linux-RAID list but the answers I found elsewhere have been contradicting one another. So, is it possible to have a swap file on a RAID-10 array? yes. mkswap /dev/mdX swapon /dev/mdX Should you use RAID-10 for swap? That's philosophy :) David - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: SWAP file on a RAID-10 array possible?
Tomas France wrote: Hi everyone, I apologize for asking such a fundamental question on the Linux-RAID list but the answers I found elsewhere have been contradicting one another. So, is it possible to have a swap file on a RAID-10 array? Yes, and very fast as well. Do note that if you (a) need to boot from a recovery CD and (b) have a low memory machine which really needs swap early, most of the ones I've tried don't use such a swap, you have to start it by hand. Also, I have not tried suspend to disk and restore using RAID-10, it's on my to-do list, but *way* down. But in general you will find it very fast and reliable. -- bill davidsen [EMAIL PROTECTED] CTO TMR Associates, Inc Doing interesting things with small computers since 1979 - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: SWAP file on a RAID-10 array possible?
Tomas France wrote: Thanks for the answer, David! I kind of think RAID-10 is a very good choice for a swap file. For now I will need to setup the swap file on a simple RAID-1 array anyway, I just need to be prepared when it's time to add more disks and transform the whole thing into RAID-10... which will be big fun anyway, for sure ;) By the way, you don't really need raid10 for swap. Built-in linux swap code can utilize multiple swap areas just fine - mkswap + swapon on multiple devices/files. This is essentially a raid0. For raid10, one thing needed is the mirroring, with is provided by raid1. So when you've two drives, use single partition on both to form a raid1 array for swap space. If you've 4 drives, create 2 raid1 arrays and specify them both as swap space, giving them appropriate priority (prio=xxx in swap line in fstab). With 6 drives, have 3 raid1 arrays and so on... This way, the whole thing is much simpler and more manageable. /mjt - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
