Raid Card To Help With Iowait
Dec 17, 2007
I was wondering if anyone has had luck with 3ware 9650's in a RAID 10 to help bring down iowait?
I currently have a VPS node that see's spikes in iowait and i'd like to bring it down. I've been considering getting a 9650 in a JBOD setup (so then I don't need to reinstall the whole node) with a battery backup to enable the cache.
My two questions are:
- In JBOD, does the write cache enable at all?
- Would the write cache help bring down the iowait much?
Drive wise we have 4 x 500GB drives in a raid10 (soft for now).
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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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Sep 8, 2009
I was building a 1u server a month or so ago to colocate. After screwing up the purchase of the raid card (got a pci 64 or something) its been sitting next to me not doing much. I need to go ahead and find a good raid card and get this colocated,
I have literally spent hours on Newegg, Amazon and Ebay and found nothing that really jumps out at me. When people were helping with the build before, Adaptec was recommended, but the card is now deactivated on newegg so I am looking again.
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Apr 14, 2008
I am currently using areca Raid card with Centos 5 which allows me to configure Raid 6 with SAS drives. But it is really costing a bomb not to say that the lead time in ordering the card is long. Performance wise is fantastic though. Anyone know of any cheaper alternative to areca that can support Centos 5 and Raid 6 SAS Drives?
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Mar 20, 2008
Anyone know what is a suitable SATA Raid card that supports Centos 4.4/4.6? I tried 3ware 9550 it is suppose to support Centos 4.4, but gives a kernel panic instead.
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Nov 7, 2009
we have some supermicro 6016-MT with 4 x SATA2 Harddrives, and would like to use raid 1/5/10.
On Dell, its very "easy" to find a raid controller, and i have never been worried about this before, but with supermicro im a little confused.
Server: supermicro.com/products/system/1U/6016/SYS-6016T-MT.cfm
I was looking at Adaptec 3405, ( adaptec.com/en-US/support/raid/sas_raid/SAS-3405/ ) but are not sure if this is the right card for this server. Is this overkill or to small a card for a 4 disk 1u server?
About cabling: On Adaptec's site they state
"Cable: one Mini SAS x4 to (4x) SATA fanout cable w/ sideband (2247000-R), 0.5 meter"
But are this cable the correct one for a server like this with backplane and everything, or should i look for a special cable? if so, anyone know what i need to order?
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Jun 20, 2008
We've got a couple of Dell SC440's that we use for low end stuff. We need one with RAID-1 so after talking with our Dell rep we ordered a 5iR card and the corresponding SATA cables. The cables are kind of funky in that the drive end of the cable has both the SATA and power connector in one "thing". You then plug the SATA power into the back of this (it piggy backs on). Once you have done all that the cover won't fit back on as the power connectors stick about 1/2" in beyond the case.
Anyone out there have a SC440 with RAID so we can compare notes?
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Oct 8, 2007
I have bought 4 servers with DELL SAS 5/iR.
All is fine but the writes are very slow; I supose it's because write cache not enabled.
I have enable it and make some test and there is a lot of difference:
[url]
I'm worried about enabling it because if the server goes down I think it can cause disk corruption and loose data and maybe the OS. What do you think about that? Data is a priority!
Disks have this technology: Seagate-exclusive IRAW (Idle Read After Write) enhances data
protection by verifying—during drive idle time—that data in thedrive buffer was properly written.
The servers are on a datacenter and have RAID 1 with Cheetah® 15K.5 SAS 3Gb/s 146.8-GB Hard Drive - ST3146855SS
[url]
I'm also VERY worried about the coments about this card:
[url]
Is it true that the raid don't get rebuilded? If it is like this I don't know why I'm running raid.
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Mar 6, 2008
for a hosting server,many parts of the hardware are all important,
and some part may effect the performance and price,
i just wonder two part,
how can i judge if the raid card and chip is powerful enough to run a hosting server?
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Oct 17, 2007
Will a Perc 5 raid card work in a non-dell Linux server? These cards can be found for about $100 on eBay, and are much cheaper than the Adaptec cards with similar features and ports.
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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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Feb 22, 2007
Code:
19:28:57 up 22 min, 2 users, load average: 2.99, 3.48, 3.52
105 processes: 103 sleeping, 1 running, 0 zombie, 1 stopped
CPU states: cpu user nice system irq softirq iowait idle
total 0.0% 0.0% 0.4% 0.0% 0.2% 99.2% 0.0%
cpu00 0.0% 0.0% 0.4% 0.0% 0.4% 99.0% 0.0%
cpu01 0.0% 0.0% 0.4% 0.0% 0.0% 99.5% 0.0%
Mem: 2047220k av, 1020368k used, 1026852k free, 0k shrd, 88516k buff
515212k active, 316448k inactive
Swap: 2040244k av, 0k used, 2040244k free 672648k cached
PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME CPU COMMAND
7775 root 15 0 1344 1344 916 S 0.2 0.0 0:02 0 top
14220 root 15 0 1216 1216 920 R 0.2 0.0 0:00 1 top -c
19768 root 25 0 3764 3764 2216 S 0.4 0.1 0:00 0 /usr/local/cpanel/bin/dcpumon
1 root 15 0 544 544 472 S 0.0 0.0 0:03 0 init
2 root RT 0 0 0 0 SW 0.0 0.0 0:00 0 migration/0
3 root RT 0 0 0 0 SW 0.0 0.0 0:00 1 migration/1
4 root 15 0 0 0 0 SW 0.0 0.0 0:00 1 keventd
5 root 34 19 0 0 0 SWN 0.0 0.0 0:00 0 ksoftirqd/0
6 root 34 19 0 0 0 SWN 0.0 0.0 0:00 1 ksoftirqd/1
9 root 25 0 0 0 0 SW 0.0 0.0 0:00 1 bdflush
7 root 15 0 0 0 0 SW 0.0 0.0 0:00 1 kswapd
Was sorted by processor usage.
Code:
root@dual [/var/log]# uname -a
Linux 2.4.21-47.0.1.ELsmp #1 SMP Thu Oct 19 11:33:45 EDT 2006 i686 i686 i386 GNU/Linux
Code:
Processor Information
Processor #1 Vendor: GenuineIntel
Processor #1 Name: Intel(R) Pentium(R) 4 CPU 3.80GHz
Processor #1 speed: 3790.694 MHz
Processor #1 cache size: 2048 KB
Processor #2 Vendor: GenuineIntel
Processor #2 Name: Intel(R) Pentium(R) 4 CPU 3.80GHz
Processor #2 speed: 3790.694 MHz
Processor #2 cache size: 2048 KB
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Oct 24, 2007
I have a server with two cPanel accounts, each running gallery2. Load has been high:
[url]
[url]
[url]
Sar output (done at a less busy time):
[url]
Hardware:
1 Intel 2.4 GHz 1066FSB - Conroe Xeon 3060 (Dual Core)
2 Generic 1024 MB DDR2 667 ECC
1 Maxtor 250GB SATA 7200RPM MaxLine Plus II
1 Unknown Onboard SATA
1 Dell Single socket 1067FSB - Quad Core Capable PowerEdge 840
Howmuch %iowait is too much?
Since it's using less than 1GB Swap, there's enough RAM?
How do I get more specific than httpd as the cause of the load. The gallery script is the only thing running so is the execution time of PHP the bottleneck? If PHP and apache are single threaded would a quad core reduce load? Does lighttpd run PHP faster?
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Oct 27, 2008
Recently I've noticed named causing high iowait.
If I stop named, iowait reduces to around 40%.
Code:
10:05:55 up 1:59, 2 users, load average: 5.09, 6.73, 6.23
192 processes: 185 sleeping, 7 running, 0 zombie, 0 stopped
CPU states: cpu user nice system irq softirq iowait idle
total 4.3% 0.0% 5.0% 0.3% 0.0% 89.2% 0.9%
cpu00 4.8% 0.0% 4.8% 0.0% 0.1% 89.3% 0.8%
cpu01 3.9% 0.0% 5.2% 0.7% 0.0% 89.0% 1.0%
Mem: 1023624k av, 966688k used, 56936k free, 0k shrd, 119500k buff
658244k actv, 130464k in_d, 16084k in_c
Swap: 1052248k av, 72096k used, 980152k free 496268k cached
PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME CPU COMMAND
15 root 15 0 0 0 0 SW 0.8 0.0 2:23 1 kjournald
9182 named 15 0 3504 3504 2184 S 0.6 0.3 0:01 0 named
8301 apache 15 0 14564 11M 6832 S 0.5 1.1 0:00 0 httpd
1043 qmails 24 0 1196 1064 384 R 0.4 0.1 1:10 0 qmail-send
1047 qmailr 25 0 372 364 280 S 0.3 0.0 0:35 1 qmail-rspawn
30825 root 15 0 1140 1088 744 R 0.2 0.1 0:09 1 top
7025 apache 15 0 13536 10M 6820 S 0.2 1.0 0:00 0 httpd
7076 apache 15 0 13868 11M 6820 S 0.2 1.1 0:00 1 httpd
759 root 15 0 568 548 488 R 0.1 0.0 1:30 1 syslogd
I believe this isn't normal.
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May 30, 2009
Few weeks ago my customer began to notice problem with server load.
I look to munin graphs and see this:
http://dl.getdropbox.com/u/252944/iowait/iowait-hr.png
iowait creates high performance degradation. There was no changes in server software & configuration. Sometimes server work very slow, count of apache processes is high - there is no any processes and scripts who can use a lot of hdd resources.
Sites located on customer server does not create high load, and not subjected to any attacks.
I received response from DC:
I did some research for this and it seems that other people has experienced similar issues and is reporting that it is a kernel bug have you ran yum update to receive the latest kernel if not you can try and update and see if that may resolve your issue.
CENTOS 5.2
Cpanel / WHM
Linux *** 2.6.18-92.1.22.el5PAE #1 SMP Tue Dec 16 12:36:25 EST 2008 i686 i686 i386 GNU/Linux
I try to run "yum update kernel" but it seems installed kernel is up to date.
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Jul 14, 2009
In my server iowait is causing high load, how do we find out which are all users taking memory that could cause my server to use swap memory.
server : linux centos/Cpanel
I have tried the below commands, but how do we locate user specific,
ps aux --sort -vsz | head -25
vmstat 1
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Apr 12, 2008
Server is Xeon 3060, 3GB Ram, 250GB SATA-II HDD. I followed the recommendations made by mysqlprimer tuner script.
top - 11:54:33 up 237 days, 15:01, 1 user, load average: 6.06, 2.80, 1.65
Tasks: 133 total, 2 running, 131 sleeping, 0 stopped, 0 zombie
Cpu(s): 13.0% us, 4.9% sy, 0.0% ni, 24.3% id, 57.8% wa, 0.0% hi, 0.0% si
Mem: 3114144k total, 3096468k used, 17676k free, 30220k buffers
Swap: 2096440k total, 32348k used, 2064092k free, 2515412k cached
PID USER PR NI %CPU TIME+ %MEM VIRT RES SHR S COMMAND
8610 nobody 16 0 28 1:37.73 0.7 78908 20m 16m S lsphp4
10520 nobody 16 0 3 0:01.97 0.4 78788 10m 6884 S lsphp4
26474 nobody 15 0 2 15:04.07 0.4 14196 11m 3216 S lshttpd
28275 mysql 22 6 1 131:28.83 7.4 733m 224m 2700 S /usr/sbin/mysqld --basedir=/ --datadir=/var/lib/mysql --user=mysql --pi
Code:
[mysqld]
max_connections=500
max_user_connections=300
skip-locking
skip-innodb
query_cache_limit=1M
query_cache_size=64M
query_cache_type=1
interactive_timeout=60
wait_timeout=60
connect_timeout=6
thread_cache_size=128
key_buffer_size=640M
max_allowed_packet=16M
table_cache=2048
join_buffer=1M
sort_buffer=2M
record_buffer=1M
sort_buffer_size=2M
read_buffer_size=2M
safe-show-database
max_connect_errors=10
thread_concurrency=2
myisam_sort_buffer_size=64M
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
#log_slow_queries=/var/log/mysql/mysql_slow-queries.log
long_query_time=3
tmp_table_size=32M
max_heap_table_size=32M
#log-queries-not-using-indexes=/var/log/mysql/mysql_queries_no-indexes.log
join_buffer_size=2M
low_priority_updates=1
read_rnd_buffer_size=2M
[mysql.server]
user=mysql
basedir=/var/lib
[safe_mysqld]
err-log=/var/log/mysqld.log
var/lib/mysql/mysql.pid
open_files_limit=8192
[mysqldump]
quick
max_allowed_packet=16M
[mysql]
no-auto-rehash
[isamchk]
key_buffer=32M
sort_buffer=32M
read_buffer=16M
write_buffer=16M
[myisamchk]
key_buffer=32M
sort_buffer=32M
read_buffer=16M
write_buffer=16M
[mysqlhotcopy]
interactive-timeout
Whenever there are a lot of members online on my forum, the iowait shoot up, >30% and often times hovering at 60%. It'll eventually drop down to normal levels. However, during the high iowait, there are over 2.5GB of free memory according to the command, free -m
is it due to mysql not optimized or other processes? I don't think the bottleneck is on the cpu or ram.
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Nov 22, 2008
diagnosing my server which currently experiencing high iowait for weeks, I'm still figuring the root cause.
total used free shared buffers cached
Mem: 4051 3653 398 0 341 2847
-/+ buffers/cache: 464 3587
Swap: 8191 0 8191
The server spec as follow :
HP DL 380 G5
4G RAM
2.6.18-53.el5PAE
the load is around 1 or 2 , but iowait have been on the high side even the server currently is under utilized
I'm running LVM and hardware RAID 1 on the server.
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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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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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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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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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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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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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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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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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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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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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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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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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