Hi all, I'm building a backup server for a client - straight forward as far as software goes - samba share for the daily backups to go into. Hardware is a 2ghz Celeron (P4 type), 256MB ram, and four Seagate 160GB SATA discs in a RAID-5 on this controller: 000:00:07.0 RAID bus controller: LSI Logic / Symbios Logic MegaRAID (rev 01) Subsystem: LSI Logic / Symbios Logic MegaRAID SATA 150-6 RAID Controller Flags: bus master, 66Mhz, slow devsel, latency 32, IRQ 11 Memory at ef000000 (32-bit, prefetchable) [size=64K] Capabilities: [80] Power Management version 2 OS is 9.3 Pro with all updates applied. I copied the data that was on the original RAID set (3 discs) off to a 200gb Seagate PATA disc, and mc reported on the large files 27mb/s sustained write. Now, copying stuff back to the RAID set, mc reports a mere 6-7mb/s. The only thing that struck me as weird is that the controller didn't take much time to create the raid - less than a minute. Last time I made a raid (2 10krpm SCSI 74gb discs on an Adaptec card) that took a couple of hours. Any ideas why I'm getting this? 7mb/s write is not going to be enough to copy all the data before the next backup starts. Thanks Hans
Hans du Plooy wrote:
Hi all,
I'm building a backup server for a client - straight forward as far as software goes - samba share for the daily backups to go into.
Hardware is a 2ghz Celeron (P4 type), 256MB ram, and four Seagate 160GB SATA discs in a RAID-5 on this controller:
Depending on the number of smb processes you might consider giving your box a bit more RAM.
000:00:07.0 RAID bus controller: LSI Logic / Symbios Logic MegaRAID (rev 01) Subsystem: LSI Logic / Symbios Logic MegaRAID SATA 150-6 RAID Controller Flags: bus master, 66Mhz, slow devsel, latency 32, IRQ 11 Memory at ef000000 (32-bit, prefetchable) [size=64K] Capabilities: [80] Power Management version 2
How much cache does the controller have?
OS is 9.3 Pro with all updates applied. I copied the data that was on the original RAID set (3 discs) off to a 200gb Seagate PATA disc, and mc reported on the large files 27mb/s sustained write.
Now, copying stuff back to the RAID set, mc reports a mere 6-7mb/s.
This is often the case when writing on a RAID5.
The only thing that struck me as weird is that the controller didn't take much time to create the raid - less than a minute. Last time I made a raid (2 10krpm SCSI 74gb discs on an Adaptec card) that took a couple of hours.
Modern RAID controllers can initialize the RAID as a background task. That way you can immediately install your system while the controller continues to build the RAID.
Any ideas why I'm getting this? 7mb/s write is not going to be enough to copy all the data before the next backup starts.
Do you see disc activity when you copy job stops? That would probably be the background task building the RAID. If the RAID is already finished you can only tinker with hardware-addons like the battery pack, more cashe memory for the controller or change to RAID1 or RAID10. The latter would give you about 40 mb/s but sacrifice half of your capacity. Sandy
Hi, thanks for replying. Sandy Drobic wrote:
Depending on the number of smb processes you might consider giving your box a bit more RAM.
It is going to get a gig, but for now 256 has to make do. I'm not even running samba yet, just copying stuff locally.
000:00:07.0 RAID bus controller: LSI Logic / Symbios Logic MegaRAID (rev 01) Subsystem: LSI Logic / Symbios Logic MegaRAID SATA 150-6 RAID Controller Flags: bus master, 66Mhz, slow devsel, latency 32, IRQ 11 Memory at ef000000 (32-bit, prefetchable) [size=64K] Capabilities: [80] Power Management version 2
How much cache does the controller have?
64MB
Now, copying stuff back to the RAID set, mc reports a mere 6-7mb/s.
This is often the case when writing on a RAID5.
I know, but I've never seen it this slow - slower than a single disc?
Modern RAID controllers can initialize the RAID as a background task. That way you can immediately install your system while the controller continues to build the RAID.
I suspected as much.
Do you see disc activity when you copy job stops? That would probably be the background task building the RAID.
Hmm, I'm going to have to find a LED to put on the controller. The discs are completely quiet (I like Seagate :-) so it's hard to tell, but that is probably what's going on. Thanks Hans
Sandy Drobic wrote:
Modern RAID controllers can initialize the RAID as a background task. That way you can immediately install your system while the controller continues to build the RAID.
This seems to have been the problem. When I put my hear by the drives, I can hear, ever so fainly through the noise of the fans, the soft krr krr krr krr krr of the discs, even though the box is standing idle. I would much prefer to see the initialisation happening in one go though, so that I know when it is done. It has been going for a good 16 hours now and copying still gives me little over 7mb/s Thanks for your reply! Hans
Sandy Drobic wrote:
The only thing that struck me as weird is that the controller didn't take much time to create the raid - less than a minute. Last time I made a raid (2 10krpm SCSI 74gb discs on an Adaptec card) that took a couple of hours.
Modern RAID controllers can initialize the RAID as a background task. That way you can immediately install your system while the controller continues to build the RAID.
Hi guys The machine have been standing idle since friday, and this morning when got to the office it was still krr krr krr -ing away. Shouldn't it have been done creating the raid yet? It's still writing at 7mb/s odd... I'm beginning to wonder if it would be better just to use the raid controller as normal SATA controller (the card uses three Silicon Image 3112a controllers, which I know to work a lot faster), and create a software raid? Is this card even properly supported (as far as performance goes) under linux? I'm not finding much useful info on that.
Hans du Plooy wrote:
Modern RAID controllers can initialize the RAID as a background task. That way you can immediately install your system while the controller continues to build the RAID.
The machine have been standing idle since friday, and this morning when got to the office it was still krr krr krr -ing away. Shouldn't it have been done creating the raid yet? It's still writing at 7mb/s odd...
It can take a bit of time to complete the raid initialization, but after 2 days the task should definitely be finished.
I'm beginning to wonder if it would be better just to use the raid controller as normal SATA controller (the card uses three Silicon Image 3112a controllers, which I know to work a lot faster), and create a software raid?
I suspect the cpu of the raid controller is a bit weak. Software raid would probably be a lot faster, but then you would lose the comfort of hardware raid. Though, if you don't have hotplug drives and need to down the computer anyway to replace a faulty drive you might as well install software raid. Provided your server has the cpu power to spare. I would write down all steps necessary to replace a drive BEFORE you need it, though and put that how-to next to the server. (^-^) It might save you some real headache and sweat in the future. Sandy
Sandy Drobic wrote:
I'm beginning to wonder if it would be better just to use the raid controller as normal SATA controller (the card uses three Silicon Image 3112a controllers, which I know to work a lot faster), and create a software raid?
I suspect the cpu of the raid controller is a bit weak. Software raid would probably be a lot faster, but then you would lose the comfort of hardware raid.
That's alright, the server is not mission critical - it is merely for storage of backups.
Provided your server has the cpu power to spare.
That's the part I'm worried about. If the hardware choices were mine, it would have been an Athlon with a 3ware card... Thanks Hans
Hans du Plooy wrote:
I suspect the cpu of the raid controller is a bit weak. Software raid would probably be a lot faster, but then you would lose the comfort of hardware raid.
That's alright, the server is not mission critical - it is merely for storage of backups.
The question is rather if you have the experience how to handle a drive replacement of a software raid. If you do I would just give it a try.
That's the part I'm worried about. If the hardware choices were mine, it would have been an Athlon with a 3ware card...
I have not used a 3ware card yet, but seen mostly approving reviews. Is it possible to ask your vendor if he can explain the miserable write throughput of the LSI card? Sandy
Sandy Drobic wrote:
That's alright, the server is not mission critical - it is merely for storage of backups.
The question is rather if you have the experience how to handle a drive replacement of a software raid. If you do I would just give it a try.
I have had to do it once. The notes are somewhere in a deep dark corner of my notebook's hard disc... :-)
That's the part I'm worried about. If the hardware choices were mine, it would have been an Athlon with a 3ware card...
I have not used a 3ware card yet, but seen mostly approving reviews. Is it possible to ask your vendor if he can explain the miserable write throughput of the LSI card?
I don't think I have ever read a disapproving review of 3ware cards. As for the LSI card, it did work quite a bit faster before I added the fourth drive, but that was under Win2k3 server, and I didn't set that one up - no idea how long it took to finish. Thanks Hans
Sandy
On Mon, 2005-08-29 at 23:16 +0200, Hans du Plooy wrote:
Sandy Drobic wrote:
That's alright, the server is not mission critical - it is merely for storage of backups.
The question is rather if you have the experience how to handle a drive replacement of a software raid. If you do I would just give it a try.
I have had to do it once. The notes are somewhere in a deep dark corner of my notebook's hard disc... :-)
That's the part I'm worried about. If the hardware choices were mine, it would have been an Athlon with a 3ware card...
I have not used a 3ware card yet, but seen mostly approving reviews. Is it possible to ask your vendor if he can explain the miserable write throughput of the LSI card?
I don't think I have ever read a disapproving review of 3ware cards. As for the LSI card, it did work quite a bit faster before I added the fourth drive, but that was under Win2k3 server, and I didn't set that one up - no idea how long it took to finish.
Thanks Hans
I see a lot of people talking about SATA RAID cards lately. So I will chime in. First of I am in no affiliation with this company or anyone that deals with them. If you want reliable fast performance and want to go the cheap SATA route then I would suggest getting a Areca card. http://www.areca.com.tw/index/html/ The performance appears to be almost double that of any other SATA RAID card. They offer up to a 24 port card as well as PCI-E support. They have full SuSe driver support for 9.0 to 9.3 32bit and 64bit. Hope this help someone. Brad Dameron SeaTab Software www.seatab.com
participants (3)
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Brad Dameron
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Hans du Plooy
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Sandy Drobic