RAID 1 Swap

Oct 28, 2007

I have two servers, HP RAID and DELL RAID.

Both controllers are set to RAID 1

I want to take the 2 HD from HP, and put into Dell.

Would this ruin my HD? Will I break the RAID and all my files be lost?

How can I achieve this without loosing my files?

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400GB Hard Disk Drives In RAID 0, RAID 5 And RAID 10 Arrays: Performance Analysis

Mar 7, 2007

Quote:

Today we are going to conduct a detailed study of RAIDability of contemporary 400GB hard drives on a new level. We will take two "professional" drives from Seagate and Western Digital and four ordinary "desktop" drives for our investigation. The detailed performance analysis and some useful hints on building RAID arrays are in our new detailed article.

[url]

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Hardware RAID: Is Motherboard RAID As Good As A Dedicated PCI-E Card

Mar 24, 2008

Is Motherboard RAID as good as a dedicated PCI-E card? I am guessing a dedicated card is the best option, though costs more.

We are looking at buying a barebones server from Supermicro. It features an onboard RAID controller which supports RAID 0, 1, 5 & 10 - but for some strange reason it will only support RAID 5 if you use Windows. Here is a link to the page detailing the RAID features.

[url]

We are going to be running Linux, CentOS 5.1, so we will only have the choice of RAID 0, 1 or 10. This isn't an issue, as having RAID 10 on 4x SAS (15k) drives will be fine for speed and stability. What is an issue is would this RAID controller be as fast or reliable compared to a dedicated PCI-E card? If it can only use RAID 5 in windows, does that suggest this controller is too reliant on software? It would be a nightmare to suffer downtime and data loss because the controller couldn't hack it during a drive failure, or one day it decided to bugger up the array when rebooting.

So that leads me to looking at this card, this looks very good for what we need. Are adaptec a reliable brand? I've seen it advertised for £200, which is a good price.

[url]

This card features RAID 5 and 6, would RAID 6 be better than RAID 10 for redundancy, or is it too slow to bother with? Also it seems to have a battery module available for it, what does this achieve? Cos surely if the power dies the hard drives and motherboard can't run off this little battery, or does it just help the controller stay alive long enough with some hard drive information in its memory if the power goes out during a rebuild?

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Any Experiences With Software-Raid 5 Vs Hardware-Raid 5? (e.g. Hetzner EQ9)

Sep 17, 2009

I could try the Software-RAID 5 of the EQ9 Server of Hetzner.

Does anyone here has experiences, how fast a hardware raid 5 compared against the software-Raid 5 is?

The i7-975 should have enough power to compute the redundnacy on the fly, so there would be a minimal impact on performance. But I have no idea.

I want to run the server under ubuntu 8.04 LTS x64.

On it a vitualisation like VMware the IO-Load could get really high.

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Whats The Best For Server With SATA Raid 1 And SCSI Raid 10

Jan 14, 2008

So I've just got a server with 2xSATA raid 1 (OS, cpanel and everything in here) and 4xSCSI raid 10 (clean).

Which one do you guys think will give the best performance:

1. Move mysql only to 4xSCSI raid 10
2. Move mysql and home folder to 4xSCSI raid 10

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How To Setup Software RAID-10 On Linux With /boot On RAID-1

Jul 8, 2007

I am in a somewhat complicated situation... I wanted to order a custom server with hardware 3Ware RAID controller but after over a month of waiting I was told the HW RAID controller, as well as any other 3Ware controller they tried, does not work with the motherboard used in the server from Fujitsu-Siemens and that they simply got a reply from FS that the controller is not certified to work with their motherboard.

So although I'd prefer a HW raid, I am forced to either choose a different webhost or setup a software RAID. The problem is, I haven't done that before and am somewhat moderately...scared

I have read a lot of the info about SW RAID on Linux that I could find through Google but there are some questions unanswered still. So I thought that perhaps some of the more knowledgeable WHT members could help me with this problem...

The server specs will be:

Core2Duo E6600 (2.4Ghz), 2GB RAM, 6-8x* 250GB SATA II HDDs, CentOS 4.4 or SuSe, DirectAdmin

* I prefer 8 HDDs (or actually 9) over 6 but I am not sure if their server chassis can hold that many HDDs, I am awaiting answer from them. They don't have any other drives beside the 250GB ones so I am limited to those.

The preferred SW RAID setup is to have everything in RAID 10, except for the /boot partition which has to be on RAID-1 or no RAID I believe, plus one drive as hot spare (that would be the 9th drive). I am quite sure they will not do the setup for me but will give me access to KVM over IP and a Linux image preinstalled on the first HDD so that I'll have a functional system that needs to be upgraded to RAID-10.

How do I do that? The big problem I see is that LILO or GRUB can't boot from a software RAID-5/10 so I will have to mount the /boot partition elsewhere. It's probably terribly simple...if you have done it before which I have not. I have read some articles on how to setup a RAID-5/10 with mdadm (e.g. [url] ) but they usually do not talk about how to setup the boot partition. Should it be setup as a small sized (100-200MB) RAID-1 partition spread over all of the drives in the otherwise RAID-10 array?

What about swap? Should I create a 4-8GB (I plan to upgrade the server RAM to 4GB in near future) RAID-1 swap partition on each of the disks or swap to a file on the main RAID-10 partitions. The second sounds simpler but what about performance? Is swapping to a file on RAID-10 array a bad idea, performance wise?

Is it possible to grow a RAID-10 array in a way similar to growing a RAID-5 array with mdadm (using two extra drives instead of one of course)? mdadm doesn't actually even mention RAID-10 despite it does support it without having to create RAID-0 on top of RAID-1 pairs if the support is in kernel, from what I know.

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Worth Having RAID 1 If Raid Arrays Break

Feb 25, 2009

How often do RAID arrays break? Is it worth having RAID if a servers hard drive goes down? I was thinking it may just be a better option to just have a backup drive mounted to my system and in the even of a system failure just pop in a new hard drive, reload the OS, and then reload all my backups?

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Software Raid 1 - Rather Slow During Raid 1 Recovery

May 20, 2009

I have a new server and it is rather slow during raid 1 recovery after system installed

CPU: Intel Core2Duo E5200 Dual Core, 2.5Ghz, 2MB Cache, 800Mhz FSB
Memory: 4GB DDR RAM
Hard Disk 1: 500GB SATA-2 16MB Cache
Hard Disk 2: 500GB SATA-2 16MB Cache

root@server [~]# cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 sdb1[1] sda1[0]
256896 blocks [2/2] [UU]

md1 : active raid1 sdb2[1] sda2[0]
2096384 blocks [2/2] [UU]

md2 : active raid1 sdb4[2] sda4[0]
480608448 blocks [2/1] [U_]
[=======>.............] recovery = 36.7% (176477376/480608448) finish=1437.6min speed=3445K/sec

the sync speed is just 3.4Mb/second and the total hours needs to be more than 40 hours

Also the server load is very high (nobody uses it)

root@server [~]# top
top - 07:00:14 up 16:55, 1 user, load average: 1.88, 1.41, 1.34
Tasks: 120 total, 1 running, 119 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.0%us, 0.2%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.0%hi, 0.2%si, 0.0%st
Mem: 4148632k total, 747768k used, 3400864k free, 17508k buffers
Swap: 5421928k total, 0k used, 5421928k free, 569252k cached

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RAID 5 Vs RAID 10 In Shared Hosting Server

Oct 22, 2009

I am in the process of restructuring the infrastructure on our servers. I am thinking of using either RAID 5 (1 hot spare) vs RAID 10 as my 1U server has 4 HDD tray.

RAID 5 would have better capacity but RAID 10 has better overall performance. Which one do you guys go for a shared hosting server?

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Turn Non Raid Into Raid On Live Server

Dec 23, 2008

Is it possible to turn a non raided setup into Linux software raid, while it is live, and if it's the OS drive? Can you even software raid the OS drive remotely? I've been thinking about doing it for the redundancy (and possible slight performance boost for reads, but doing it more for redundancy). I'm using CentOS.

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Read Raid-disk On Non-raid System

May 22, 2008

I want to take some data from a raid-disk (taken from a raid-1 sstem). Put it into a new system already, but this system doesn't have any raid.

When viewing "fdisk -l", it said /dev/sdb doesn't contain valid partition. Is there anyway I can mount it now? I am on CentOS 4 box

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3ware RAID Or Software RAID

Mar 24, 2009

MY server configure our drives with RAID-1.

How can I check it my server configure with 3ware or software raid ?

Also please advise me how can I monitor raid configuration that my raid is working fine or no ?

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RAID Or Not To RAID: Trying To Decide On A New Server

Jul 11, 2008

I've been talking to the Planet about trading in my four and a half year old "SuperCeleron" (from the old ServerMatrix days) Celeron 2.4 GHz system for something new. As part of their current promotions, I've configured a system that looks decent:

Xeon 3040, 1 gig of RAM, 2x250GB hard disks, RHEL 5, cPanel+Fantastico, and 10 ips for $162.

Not too bad. I could bump up the ram to 2 gb for, I think, $12 more, which I'm thinking about and wouldn't mind some thoughts on. But, the thing that has me really confused is RAID. I like the idea of doing a RAID 1 setup with those two hard disks. But, the Planet wants $40/month for a RAID controller to do it. I really don't want to go over $200 a month!

Any thoughts on alternative redundancy strategies that might avoid that cost? Software RAID does not seem to be offered by the Planet, unless I can figure out how to do it after installation (is that possible?) Better ideas in general on the server?

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Raid 1 SCSI Or Raid 10 SATA 10k

May 23, 2007

Just curious what your thoughts are on performance:

2 SCSI Drives 10k w/RAID 1

or

4 SATA 10k w/RAID 10

Prices are not too different with 4 drives just being a tad more.

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Software Raid Vs. Hardware Raid

Jun 5, 2007

how well software raid can perform and how it compares to hardware raid. How does software raid actually work and is it worth it?

How should I look at be setting up software raid if I was going to? Would you recommend just to use hardware raid instead?

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RAID 10 Or RAID 5 With Online Backup

Dec 10, 2007

Which do you guys recommend of the following?

4x 73GB 15,000rpm SAS drives in a RAID 10

or

4x 73GB 15,000rpm SAS drives in a RAID 5 w/ online backup

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Run Out Of Swap

Apr 19, 2009

What would cause a Linux server to run out of swap? Would it be a memory leak? This happened today to my server and it had to be forcefully rebooted by the data center.

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Swap Not Being Used

Apr 25, 2008

My server load is up to 20 sometimes, all RAM is used but only a very little SWAP is used (never go above 3M). IOwait is also very high

top - 09:55:33 up 94 days, 3:35, 2 users, load average: 19.09, 9.43, 6.18
Tasks: 327 total, 2 running, 325 sleeping, 0 stopped, 0 zombie
Cpu(s): 38.0% us, 2.0% sy, 0.0% ni, 0.0% id, 59.5% wa, 0.0% hi, 0.5% si
Mem: 2056272k total, 2034064k used, 22208k free, 47516k buffers
Swap: 1052248k total, 3572k used, 1048676k free, 800656k cached

I tried swapoff, mkswap and swapon but it is still the same.

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Swap Used At 100%

Jul 6, 2007

do i need to upgrade my server if it looks like this?

I have one website running on it.

[url]
*sign* I'm not really sure why it's running like this.

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High Swap

Mar 31, 2009

I've got a dedicated with LW.

I've had it for a while and during that time I've never seen the swap memory go over 20%.

A month or so ago, I had the server upgraded to 8GB of ram to make room for more planned sites.

Since then, the swap memory has gone rampant. It regulary goes to 93% used with less than 20% of the regular ram and really no load on the server.

I've contacted support twice about it and was told don't worry it's normal.

From what I've read in the cpanel forum, no it's not normal and may in fact be caused by bad ram chips and if it hits 100% could freeze the server.

There are no processes or users causing it, so It's something else.

Has anybody had this type of problem that they resolved and could share what they did to resolve it?

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CPanel - Swap Used 100%

Jul 22, 2008

My swap is currently at 100% and my website isnt loading. What does swap mean and is this the reason my site isnt loading?

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Swap Not Working

Mar 1, 2008

i want to know why the swap in the server didn't work he is always 208k used

see my top status

top - 09:41:51 up 4 days, 12 min, 2 users, load average: 2.05, 3.11, 3.33
Tasks: 185 total, 2 running, 181 sleeping, 2 stopped, 0 zombie
Cpu(s): 0.7% us, 1.0% sy, 1.6% ni, 92.4% id, 4.3% wa, 0.0% hi, 0.0% si
Mem: 4148808k total, 4008248k used, 140560k free, 117488k buffers
Swap: 2096440k total, 208k used, 2096232k free, 3016032k cached

cat /etc/fstab

LABEL=/ / ext3 defaults,usrquota 1 1
LABEL=/boot /boot ext3 defaults 1 2
none /dev/pts devpts gid=5,mode=620 0 0
none /dev/shm tmpfs noexec,nosuid 0 0
LABEL=/home /home ext3 defaults,usrquota 1 2
none /proc proc defaults 0 0
none /sys sysfs defaults 0 0
LABEL=/tmp /tmp ext3 defaults 1 2
LABEL=/usr /usr ext3 defaults,usrquota 1 2
LABEL=/var /var ext3 defaults,usrquota 1 2
LABEL=SWAP-sda7 swap swap pri=0,defaults 0 0
/dev/sdb1 /hdd1 ext3 defaults,usrquota 0 0
/tmp /var/tmp ext3 defaults,bind,noauto 0 0
/dev/hdb /media/cdrecorder auto pamconsole,exec,noauto,managed 0 0
/dev/scd0 /media/cdrom auto pamconsole,exec,noauto,managed 0 0

My box

WHM 11.15.0 cPanel 11.18.1-R20683
CENTOS Enterprise 4.6 i686 on standard - WHM X v3.1.0

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Why Do PHP Caches Use Swap

Feb 20, 2008

Opcode caches have stability problems with some PHP apps:

[url]

I've been trying to get XCache working with gallery2, right now apache has to restart every 2-4 hours but it's been worse at times and it'd be nice to know what's going on

I noticed that both XCache and eAccel use a small amount of swap space all the time, it grows slowly and if I'm lucky enough to go without a segfault it will reach maybe 4MB. That's not a lot but it doesn't happen at all without a PHP cache (swap stays locked at 72kb unless RAM runs out and the server thrashes).

Here's the error and my settings:

[Tue Feb 19 06:19:55 2008] [error] PHP Warning: Invalid argument supplied for foreach() in /home/cityv4/public_html/gallery/modules/customfield/classes/CustomFieldHelper.class on line 233
[Tue Feb 19 06:19:55 2008] [error] PHP Warning: Invalid argument supplied for foreach() in /home/cityv4/public_html/gallery/modules/customfield/classes/CustomFieldHelper.class on line 233
[Tue Feb 19 06:19:56 2008] [notice] child pid 31028 exit signal Segmentation fault (11)
[Tue Feb 19 06:19:56 2008] [notice] child pid 10638 exit signal Segmentation fault (11)

[url]

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CPanel - Swap Used 100%

Jul 22, 2008

My swap is currently at 100% and my website isn't loading. What does swap mean and is this the reason my site isn't loading?

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Swap Space For VPS

Oct 1, 2007

I have purchased several VPS from a provider and found they do not provide swap space with VPS, and even with 256MB ram, I get 'out of memory' trying to compile a perl library... Creation of a swap file by myself doesn't work (operation is not permitted).
Hosting providers runs HyperVM.

So the question. Is it common or is it a misconfiguration? For now I got just 'checking on this for you' and three days of silence from their support.

I'm not opening hosting provider name, but I will if they say "You must pay for more RAM", just because other 5 VPS providers support my VPS servers with swap space.

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Xen And The Issue Of Swap

Jun 4, 2007

I have talked with the moderators and they have agreed that I can start a new thread to clarify the issue of Xen and swapping as long the discussion remains technical.

For people who are curious, I would first like to explain why this is important. What we have here is someone making a specific technical accusation against Xen, and if it is indeed crucial, it needs to be solved, or otherwise people have to know it before they get into Xen.

Claim Number 1: The original claim is that users can create arbitrarily large swap and this can lead to the equivalent of overselling.

Fact: Arbitrarily large swap has absolutely zero effect on a normal system, since Linux treats swap as an auxiliary storage, and will not use it unnecessarily. Linux will always use the RAM to the full, but swap is used only when all the buffers have been cleared. If you run free on a dedicated hardware, you will see that swap usage is most of the times zero, even though you have assigned a very large swap to the system. In fact, you can try this by simply increasing the swap to very huge value, you will see that Linux will ignore it completely.

For large swap to cause a problem, the user not only has to assign a large swap, he has to run a really huge workload on his limited RAM, and this being physically impossible, will cripple his vps long before it has any serious impact on the host.

I think the above has been agreed to by the person who made the initial claim.

Claim Number 2 Merely having a swap can lead to vps getting slowed down.

Fact ; The use of swap does not mean thrashing .

Thrashing is a technical term, and it means that the application is registering a swap hit every few instructions. This is rare in normal systems, because of a property of programs that execution is always localized. That is, at any particular time, a certain portion of the program will be continuously being executed, and other portions would be idle. Linux has algorithms that will swap out the Least Recently Used page, and this will mean that the system will not run into too many swap hits.

Now again, like in the earlier case, there will be trouble if the vps customer is trying to run a 1GB workload in a 64MB RAM. This will actually cripple his vps, which is what's the right thing to happen. So normal usage of Swap will not lead to disk I/O, since Linux has explicit algorithms to reduce swap usage.

So for minor OverUsage of memory:

For virtuozzo: the application will crash

For Xen: there will be a very minor degradation of quality. And sometimes it won't have any affect at all, since as I said, just because swap drive is non-empty doesn't mean that linux is constantly swapping out.

So summarizing:

a) Inordinately large swap has zero effect on Linux

b) Non-empty swap doesn't mean that the system is registering swap hits. For normal workloads, the swap hits will be very minimal.

And an extra advice is that if you are using Xen, don't ever use snapshoting, as it will double the disk I/O, and the worst thing is that the vps that's causing this will not even be penalized. The overhead will be completely borne by the system.

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To Swap Or To Burst

May 11, 2007

I'm planning to get a small VPS (128 MB).

I've come across a XEN based plan that offers additional 256MB swap space, and a few others Virtuozzo based plans that offer bursting capability (some even upto 8GB).

Which would be the better option?

Also, in Virtuozzo, will SLM allocation be significantly more beneficial than UBC for a small VPS?

Another question ... DirectAdmin officially claims to be able to run on a minimum of 64MB RAM. How would it perform on a 128 MB VPS ?
I'm not really looking to do much, only to host a few (5-6) small sites along with some other non-webhosting applications (which is the reason for getting a VPS instead of a reseller).

I've seen most people suggest atleast 256MB for DirectAdmin, but that is beyond my budget. (I'm also seriously considering the option of employing vi as a control panel to further conserve my limited resources)

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Server Way Too Eager To Swap

Mar 30, 2009

I have a handful of machines running Rails on CentOS 5, each with 8GB RAM. They're monitored with Nagios, so I get paged if we exceed 80% memory usage usage or 2% swap. FWIW, they're primarily dual x. dual-core Opterons, and we're using PAE.

The problem is that I keep getting paged in the middle of the night for situations where we're using 2-20% swap yet there are still several gigs of RAM free.

On some level, this makes sense -- if nothing is using a big chunk of RAM, we might as well move it out to disk. On the other hand, when there's still several gigs of RAM free, I don't see any point in bothering, especially when it causes me to get paged at 2am.

So my question is threefold:

Is there any easy way to see what's using swap? top can be made to show a swap column, but it's not what you'd think it is. (For example, most processes show as using lots of swap, and the sum vastly exceeds the actual size of our swap partition.) Can I get a list of what processes are actually swapped out to disk?

Is this a problem other people have? Are others just less aggressive in getting alerted at swap usage, or does this not happen to other people? Our setup is probably not too common (Opterons, PAE, adn 8GB on an older CentOS release?), which makes me think there's a small chance a bona fide bug plays into this somehow.

Is this a case for playing with the swappiness sysctl to make the machine less obsessed with swapping things out to disk? And if so, is there any good documentation on what the 0-100 value actually means, beyond the one sentence explaining that 100 is most likely to swap and 0 is least? Does the current setting of 60 "mean" anything, for example? 98% of the stuff online is just a mirror of the e-mail thread in which Andrew Morton and others go back and forth about what setting is ideal, which doesn't help and is tiring to read over and over.

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Correct Way To Clear Swap

May 19, 2009

I've never needed or used swap, but I justed noticed i have 523k of it, which i'm guessing happened when I restored a big CPanel account.

Anyway, is their a correct way to restore it? I've got the memory space, and I've vm.swappiness set to 0.

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How Can I Identify What Is Using My Swap Memory

Apr 19, 2009

if there is any specific way (maybe logs) to see what is using the swap memory of a dedicated server..


its a server with 8GB ram.. it has 60% of memory used, and a constant swap memory usage of 30%.. i thought that in normal conditions swap memory was not used..

its a centos / cPanel/WHM based server

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