On 29 August 2007, "Ross S. W. Walker" rwalker@medallion.com wrote:
Message: 39
<snip>
I wouldn't worry too much about the OS HD configuration, you are always going to want RAID1 for the OS, whether software or hardware.
Reason I say not to worry too much about the OS HD config is because you are almost certainly going to put the application or user data on a separate array, so the OS HD is basically used for loading binaries.
Ross: Thank you! I also read your reply to Israel in Cuba, which may be applicable for me.
About 10 seconds after I started this thread, I remembered a long discussion about RAID, SATA, etc., 2 or 3 months ago. I think that Feizhou (?) strongly recommended going with Software RAID in CentOS. I will search for that and do a lot of reading. RAID 1 for mirroring is what I want. Lanny
About 10 seconds after I started this thread, I remembered a long discussion about RAID, SATA, etc., 2 or 3 months ago. I think that Feizhou (?) strongly recommended going with Software RAID in CentOS. I will search for that and do a lot of reading. RAID 1 for mirroring is what I want. Lanny
Whoa there!
Hardware raid + battery backed up memory cache in raid 1,10 mode is hard to beat with software raid and hardware raid offers data integrity guarantee beyond software raid.
If you were planning a huge array especially a raid5 array, then software raid may be better. Hardware RAID cards all come with memory caches now so their throughput is no longer limited.
Another route you can go is getting a PCI/PCIe/PCI-X BBU RAM/NVRAM card to put an external journal on to speed up fsync performance for filesystems like ext3 over software raid since these cards can go beyond 1GB of memory unlike hardware raid cards that usually max out at 256MB.
Software RAID is also good if you need to be able to transfer the disks to another box that does not have a hardware raid controller or the same controller.
Weigh these in your decision. :-)
From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On Behalf Of Feizhou
About 10 seconds after I started this thread, I remembered
a long discussion about
RAID, SATA, etc., 2 or 3 months ago. I think that Feizhou
(?) strongly recommended
going with Software RAID in CentOS. I will search for that
and do a lot of
reading. RAID 1 for mirroring is what I want. Lanny
Whoa there!
Hardware raid + battery backed up memory cache in raid 1,10 mode is hard to beat with software raid and hardware raid offers data integrity guarantee beyond software raid.
If you were planning a huge array especially a raid5 array, then software raid may be better. Hardware RAID cards all come with memory caches now so their throughput is no longer limited.
Another route you can go is getting a PCI/PCIe/PCI-X BBU RAM/NVRAM card to put an external journal on to speed up fsync performance for filesystems like ext3 over software raid since these cards can go beyond 1GB of memory unlike hardware raid cards that usually max out at 256MB.
What are some of these BBU NVRAM cards that I keep hearing people talk about? I would love to check them out.
Software RAID is also good if you need to be able to transfer the disks to another box that does not have a hardware raid controller or the same controller.
Weigh these in your decision. :-)
For 2 SATA hard disks used for the OS I think HW RAID is overkill.
Besides I do not believe the PERC 5IR has BBU cache, that controller is really only meant as a simple RAID1 controller for the OS.
If you use HW RAID you will need to install the manufacturer's software for monitoring it for a hard disk failure.
If you wanted to add additional storage, say a SAS/SATA enclosure of 15 disks, then I would definitely invest in a HW RAID card for that!
-Ross
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Another route you can go is getting a PCI/PCIe/PCI-X BBU RAM/NVRAM card to put an external journal on to speed up fsync performance for filesystems like ext3 over software raid since these cards can go beyond 1GB of memory unlike hardware raid cards that usually max out at 256MB.
What are some of these BBU NVRAM cards that I keep hearing people talk about? I would love to check them out.
http://www.umem.com/Umem_NVRAM_Cards.html http://www.gigabyte.com.tw/Products/Storage/Products_Overview.aspx?ProductID...
Weird...I thought the umem cards were more than just BBU SDRAM but...hmm...
Software RAID is also good if you need to be able to transfer the disks to another box that does not have a hardware raid controller or the same controller.
Weigh these in your decision. :-)
For 2 SATA hard disks used for the OS I think HW RAID is overkill.
Depends. HW RAID + BBU CACHE vs SW RAID vs SW RAID + NVRAM...You cannot say overkill in certain cases.
Besides I do not believe the PERC 5IR has BBU cache, that controller is really only meant as a simple RAID1 controller for the OS.
Dell certainly has a BBU cache option, not sure if OP's Poweredge box has that option.
If you use HW RAID you will need to install the manufacturer's software for monitoring it for a hard disk failure.
Yes, likely a negative but with Dell supporting Linux maybe not so.
If you wanted to add additional storage, say a SAS/SATA enclosure of 15 disks, then I would definitely invest in a HW RAID card for that!
Depends :-D. How many hardware RAID cards offer 1GB of cache?
From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On Behalf Of Feizhou
Another route you can go is getting a PCI/PCIe/PCI-X BBU RAM/NVRAM card to put an external journal on to speed up fsync performance for filesystems like ext3 over software raid since these cards can go beyond 1GB of memory unlike hardware raid cards that usually max out at 256MB.
What are some of these BBU NVRAM cards that I keep hearing people talk about? I would love to check them out.
http://www.umem.com/Umem_NVRAM_Cards.html http://www.gigabyte.com.tw/Products/Storage/Products_Overview. aspx?ProductID=2180
Weird...I thought the umem cards were more than just BBU SDRAM but...hmm...
Thanks, I'll have to give those bad boys a look-at.
Software RAID is also good if you need to be able to transfer the disks to another box that does not have a hardware raid controller or the same controller.
Weigh these in your decision. :-)
For 2 SATA hard disks used for the OS I think HW RAID is overkill.
Depends. HW RAID + BBU CACHE vs SW RAID vs SW RAID + NVRAM...You cannot say overkill in certain cases.
I only say that because if one is really looking for high performance then more spindles then 2 will be the first thing to do and getting that data off the OS drives that may do swap under load is key too.
Besides I do not believe the PERC 5IR has BBU cache, that controller is really only meant as a simple RAID1 controller for the OS.
Dell certainly has a BBU cache option, not sure if OP's Poweredge box has that option.
Oh yes, the PERC 5e is very good, I have a couple here and they really do pull in impressive numbers even with only 256MB write-back, I of course use these with the MD1000 enclosures though.
If you use HW RAID you will need to install the manufacturer's software for monitoring it for a hard disk failure.
Yes, likely a negative but with Dell supporting Linux maybe not so.
Ah, well a lot of these are Java apps for cross-platform compatibility and some times the JavaVMs leak memory... so definitely YMMV.
If you wanted to add additional storage, say a SAS/SATA enclosure of 15 disks, then I would definitely invest in a HW RAID card for that!
Depends :-D. How many hardware RAID cards offer 1GB of cache?
Not many I can tell you that, but then again a well implemented write-back cache doesn't need a huge amount of memory to be effective.
-Ross
______________________________________________________________________ This e-mail, and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail, you are hereby notified that any dissemination, distribution or copying of this e-mail, and any attachments thereto, is strictly prohibited. If you have received this e-mail in error, please immediately notify the sender and permanently delete the original and any copy or printout thereof.
For 2 SATA hard disks used for the OS I think HW RAID is overkill.
Depends. HW RAID + BBU CACHE vs SW RAID vs SW RAID + NVRAM...You cannot say overkill in certain cases.
I only say that because if one is really looking for high performance then more spindles then 2 will be the first thing to do and getting that data off the OS drives that may do swap under load is key too.
Yes, however, sometimes you get the choice of BBU cache with hardware RAID but not more spindles you see and if the i/o is bursty then it is likely that adding extra spindles will not match RAM speeds. As for swap, I then to tune things such that swap is never in use (at least not constantly)
Besides I do not believe the PERC 5IR has BBU cache, that controller is really only meant as a simple RAID1 controller for the OS.
Dell certainly has a BBU cache option, not sure if OP's Poweredge box has that option.
Oh yes, the PERC 5e is very good, I have a couple here and they really do pull in impressive numbers even with only 256MB write-back, I of course use these with the MD1000 enclosures though.
:-)
I must admit that my viewpoint is a bit eskewed by mostly having to manage mail servers with two disk cases only.
If you use HW RAID you will need to install the manufacturer's software for monitoring it for a hard disk failure.
Yes, likely a negative but with Dell supporting Linux maybe not so.
Ah, well a lot of these are Java apps for cross-platform compatibility and some times the JavaVMs leak memory... so definitely YMMV.
Ick! Have not had to touch one of these yet. But then the Compaq DL380 did not have Linux 2.6 compatible monitoring software so I did without...
If you wanted to add additional storage, say a SAS/SATA enclosure of 15 disks, then I would definitely invest in a HW RAID card for that!
Depends :-D. How many hardware RAID cards offer 1GB of cache?
Not many I can tell you that, but then again a well implemented write-back cache doesn't need a huge amount of memory to be effective.
I don't know...if the amount of i/o is enough to swamp the write-back cache, then software raid is probably going to be a better choice.
This is the only reason why 3ware 750x and 3ware 850x boards sucked for RAID5 performance. They were powerful enough processor wise for normal conditions but they had no write-back cache and so software raid would make them lick the dust. Come degraded mode and those boards will cry and you will too. I don't know about the 955x series in degraded mode though but a 10 disk RAID5 array in normal mode with write-back cache of 128MB was pretty decent as a mail queue.
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Feizhou -
Lanny Marcus -
Ross S. W. Walker