RAID options on PE2800 3

[SirBC]

I'm trying to configure a Poweredge 2800 on the Dell website with the following setup:

RAID 1 (2x36 GB) for OS
RAID 5 (4x36 BG and 1 hot spare) for data

But the only split backplane option I see is a "2X4 Hot-Pluggable Split Backplane,PE2800". Does that mean I can't have 2 ports on one channel and 6 on the other? Or is that something I would have to call and have them configure for me?

Thanks!

-Dave

 

[twwabw]

If you want to keep your OS on a seperate array (which is a great idea) then on the 2800 the best solution is to configure the "media bay" array option. This gives you a 2-bay hot-swap cage above the main drive bays, where you can install 2 drives as a RAID1 mirror for the OS. You can then use the remaining convemtional backplane and bays either as a single 1x8, or split as a 4/4. Just keep in mind if you want to use the media bay option, and then also have a split backplane, this requires 3 raid channels, so you cannot use the embedded Perc4ei as your sole controller, as it only has 2 channels. You would need the 4ei, and then also add a 4DC. But if you simply want the media bay and 1x8, the 4ei will work great.

I've set several 2500's 2600's and 2800's up this way.

 

[SirBC]

So, the PERC4ei has 2 channels. I could use 1 channel for the media bay option (RAID1) and the other channel as a 1x8 RAID5. Is that correct? That sounds exactly like what I would want to do.

However, hen I try to configure it that way on the Dell site, it says I can't use the 4ei and have to choose either the 4/DC or 4eDC. Doesn't the 4ei only have one channel?

- Dave

 

[twwabw]

Yes- that's exactly how to set it up. Dell's config is a littl cryptic sometimes- you have to choose the right description for the array setup or it fails- I just went and did it that way- you need to choose the option that says " Drives attached to embedded PERC4ei RAID 5/1 (Backplane/Media Bay) [Included in Price] ". I'll pop a couple pics in a few minutes so you can see a couple I've done that way.

 

[technome]

The Perc4E on the 2800, is a dual channel interface, unless they changed it in the last few months.

You can definitely have your two arrays on the Perc adapter.
Raid 1, one drive on each channel
raid 5, 2 drives on each channel
Hotspare on either
This is the standard disk placement procedure for dual channel raids

Twwabw use of the drive cages is good if you have plans to increase the number of drives in the future, otherwise it is not for performance reasons.

If you use the 2 bay hotswap cage you would be required to use one channel of the raid connected to it or use a standard SCSI adapter connected to it. If you use a raid channel for it, there is nothing to gain, as you then have one channel for the regular array disk backplane, which will saturate the scsi bus with the use of 5 drives; any more drives will not increase performance.

If you use the 2 drive cage for the raid 1 with a standard two channel SCSI adapter, (which you will need anyway for a tape unit, as the embedded uses both the onboard scsi interfaces for the raid channels), you will be adding IRQ and CPU overhead, and system bus overhead from the disk I/O of the raid 1. Placing both arrays on the Perc controller does not add the extra IRQ delays or system bus traffic of a separate scsi adapter, adds slightly to the cpu usage, not as much as using an add on scsi adapter for disk I/O.

With using the Perc for the raid 5 and a separate scsi for raid 1, traffic for pagefile, temp files, log files, SQL, etc will be crossing the system bus, where as if the Perc is used for both arrays, this traffic is internal to the array controller, never hitting the system bus.

........................................
Chernobyl disaster..a must see pictorial

http://www.kiddofspeed.com/default.htm

 

[twwabw]

Here's a 2500, rackmount, with Raid1 media bay drives, and 3 Raid5 backplane drives:

http://home.rochester.rr.com/twwonline/files/pics/MA.jpg

And this is a 2600, rackmount, same setup. (crummy picture- sorry it's blurry).

http://home.rochester.rr.com/twwonline/files/pics/DCP_0543.jpg

At least it gives you an idea of what it will look like. Don't have any pics of the 2800 I did... sorry. Looks the same except the 2800 has 8 backple bays instead of 6.

These are great servers, impossible to beat for the $$. Haven't had any issues with them.

 

[twwabw]

Twwabw use of the drive cages is good if you have plans to increase the number of drives in the future, otherwise it is not for performance reasons.
"

I didn't say it was for performance. It is however an excellent configuration where you can afford to keep you OS on a seperate array, and data on another array.

"Raid 1, one drive on each channel
raid 5, 2 drives on each channel"

Raid5 w/2 drives?? I don't think so. Typo?

"If you use the 2 drive cage for the raid 1 with a standard two channel SCSI adapter, (which you will need anyway for a tape unit, as the embedded uses both the onboard scsi interfaces for the raid channels), you will be adding IRQ and CPU overhead, and system bus overhead from the disk I/O of the raid 1."

Who said to use the embedded SCSI adapter (or any other std scsi adapter) for the Media bay Raid 1?? This would imply software Raid 1, which I would NEVER suggest. Yes- the embedded Perc is either / or. Raid or scsi. If you use a non-emebedded raid adapters, you can use the embedded for std scsi devices like tape. If you use it the the raid key, then you need an additonal scsi adapter for tape devices.

I think you need to re-read what I posted.

 

[twwabw]

How the arrays are set up on the dual channel Perc. Also note Perc3 shows 5/1, with an additional Adaptec scsi controller I installed as this server also has a tape drive connected to it.

Perc3-

http://home.rochester.rr.com/twwonline/files/pics/Perc3Di 5-1.jpg

Perc4-

http://home.rochester.rr.com/twwonline/files/pics/Perc4 5-1.jpg

 

[SirBC]

Technome and twwabw, thanks the info. And thanks for the pictures twwabw. I'm glad you think that these are great servers for the money. I've been somewhat of a computer geek since the Vic20, building my own computers for years, but this is my first foray into the server world so I"m happy to take some good advice.

Let me see if I am understanding you both:

1. The benefit of using the media bay for a 2 drive RAID 1 is that it frees up 2 drive bays from the 8 available in the main backplane. So if I use the media bay for RAID 1 I would have all 8 drive bays in the main backplane available for the RAID5 array. But if I don't use the media bay and have the RAID1 and RAID 5 in the main backplane, I only have 6 drive bays avialable for the RAID5 array.

2. However, if I use the media bay for RAID1 on one channel of the 4ei, and the main backplane for RAID5 on the other channel, once I have 5 drives in the RAID5 array the bus would be saturated, so filling the remaining 3 drive bays wouldn't provide an additional performance increase.


And yes, I do want to use RAID1 on one channel and RAID 5 on the other.


3. (This is where I'm not quite sure if I understand). Let's say I don't use the media bay for the RAID1 array. That leaves me 6 drive bays for my RAID5 array. If 1 of those is used for a hot spare, and 1 is used for parity, I would only have 4 drive bays available for my RAID5. Is that correct? If that's the case, it seems like if I want to eventually have a (effective) 5 drive RAID5 array, I would have to use the media bay?


A couple of other questions:

4. Is there any benefit of using the PERC4e/DC over the imbedded PERC4ei? More memory, faster?? I think the Dell tech told me that imbedded would be faster, is that true? If I get the 4e/DC, is there still and imbedded controller on the mobo, so I would then have two controllers? What happens if the imbedded controller dies? Would I need a new mobo or can I just drop in a new controller chip and be up and running?

5. For a tape drive, assuming I need to backup 150 GB, can you recommend a good tape drive that doesn't cost a fortune?

Thanks!

- Dave

 

[twwabw]

1- "if I don't use the media bay and have the RAID1 and RAID 5 in the main backplane, I only have 6 drive bays avialable for the RAID5 array.
". No- you're only choices for the 8-drive main backplane are 1x8, or 2x4. So if you chose the 2x4 route, you'd use one row (4 spaces) for a 2-drive Raid1 OS, leaving 2 empty, and not usable. And then you'd have the 21nd bank of 4 filled with your (3 drive minimum) Raid5 array, with one spare space available for an additional future drive, or to configure as a hot spare.

2- " once I have 5 drives in the RAID5 array the bus would be saturated, so filling the remaining 3 drive bays wouldn't provide an additional performance increase.
"
I don't quite understand this one- maybe there's a perception issue- you have the ability of filling all 8 drives into a single Raid5 array if you want to. There are 8 slots, and you're able to fill them all. (on the same raid5 array) Also, adding additional drives doesn't add any performance- it only adds storage capacity.

3- see previous 2 answers.

4- "Is there any benefit of using the PERC4e/DC over the imbedded PERC4ei? More memory, faster?"
If you look at direct spec comparison, you'll they share almost identical spec, with the exception that the PERC4e/Di has 128Mb more cache memory.
Both are x8 PCIe, and in fact share the same processor. It all comes down to what you need to have on the server. Nulti-channel external arrays would dictate the DC, in order to have more external connectors. But for running internal, I would choose the embedded Perc every time. A lot of value, and good performance. Some would argue they don't want an embedded controller (or anything else embedded for that matter) since a failure of that component would require replacing the Mobo. Valid point, but these are pretty darn dependable. I've never had an embedded Perc fail. And it seems a waste to utilize the capabilities of the embedded for conventional SCSI interfaces (like for a tape). You can be a pretty basic SCSO controller much cheaper for those functions. Tape drive scsi is very low transfer rate, and usually even dictates going into the adapter setup and slowing down its max transfer rate to accomodate the tape drive!!

5- when it comes to tape drives, I would always suggest bundling the purchase with the Dell server. Not just because they offer it at a prett fair price (which it is), but because it puts the tape drive and software under the umbrella off the system's warranty. I f you buy it yourself seperately, you'll have a finger pointing pi**ing match when the tape drive has a problem (which is very likely- they're finicky).

As far as what tape drive to get, there's none that dopn't "cost a fortune". They're all expensive. For 160 GB, you pretty much are looking at LTO or better. VS-160 (which is a DLT variant) is 80Gb native, and a theoretical compressed capacity of 160Gb. Unlikely you'll ever achieve that full compressed capacity though. LTO is still very similar to DLT- still a linear variant, but LTO-2 has a native capacity of 200Gb. And they are much faster than the DLT/VS drives (almost 3-4x faster!). The only caveat is they don't offer the external models in their standard 2800 config utility, and if you choose the Media Bay for Raid1, this uses the space in the case usually utilized for a tape drive. If you call and have a rep quote you though, they WILL bundle an external with your purchase. Just remember to buy the pkg. wth the external SCSI controller as well. You'll be using the embedded one for Raid.

 

[technome]

Raid 1, one drive on each channel
raid 5, 2 drives on each channel"
Raid5 w/2 drives?? I don't think so. Typo?"
No typo, 2 drives on EACH channel of a raid adapter equals a 4 drive raid 5 array

"2- " once I have 5 drives in the RAID5 array the bus would be saturated, so filling the remaining 3 drive bays wouldn't provide an additional performance increase."

Yes, you can place 13 drives on a scsi channel,(backplane devices uses 1 slot equivalent on the bus per channel), but you do not want too, unless the main concern is a large amount of storage where speed not a main concern.

Bus saturation has to do with the amount of data feed by the drives to the scsi channel they are on; u320 in theory does 320 Meg/sec. A u320 channel channel handles roughly 290 m/sec in real life (difference between the 290 and 320 is normal overhead), after which any more data the drives need to place on the bus must be delayed. Roughly each drive on average place about 60-70 meg/sec on the bus, making 5 drives the sweet spot maximum per channel at the u320 rate, any more drives added, if anything, lowers an array speed under load, as addition drives add delays. Before the saturation point, each additional drive over the minimum number of drives needed to create a raid5 array, increase throughput, same for raid1, but every two drives increase throughput.

Embedded vs add-in performance...
agree, the embedded and the addin on card perform similarly, as both interfaces use the same exact chips for the raid functions, except the add-on card has the scsi chips from LSI, the embedded uses the motherboard's Adaptec chip interface. I have benched both, throughput is basically the same.
You would be hard pressed to have a program which would utilize more than 128 meg cache ram. Programs used by multiple users, utilizing much of the same data would benefit from a larger cache, such as 50 users, inputting sales orders, on basically a dedicated server for a sales department.

"So if you chose the 2x4 route, you'd use one row (4 spaces) for a 2-drive Raid1 OS, leaving 2 empty, and not usable. And then you'd have the 21nd bank of 4 filled with your (3 drive minimum) Raid5 array, with one spare space available for an additional future drive, or to configure as a hot spare."
The industry standard is dividing the drives over the channels which gives you...
(the array drives could be placed in different order but an example)...
raid 1, drive1 on channel #0, drive2 on channel #1
in the remaining slots of the 2x4 backplane.
Raid 5, drives3 on channel 0, drive4 on channel 1, drive5 on channel 0,drive 6 on channel 1, the hot spare on either channel, which could be designated as a global hotspare, which would make it a hotspare for the raid1 or the raid 5, should either lose a drive. Very little safety is gained by not dividing drives over multiple channels of a raid adapter, as most chips are shared over the channels.

As far as economics of the embedded vs the addin card.. with the embedded you will need a scsi card for the tape drive, you can not place a tape unit on a raid channel which has dives on it, as it will almost certainly cause the arrays to fail at some point in time.
The main advantages of the addin, is the ability to transfer the array to similar hardware directly, or dissimilar hardware with a "repair" install, the addin card has a choice of using internal or external scsi ports if you purchase the correct model, plus larger cache options. Last but not least, the addin cards WILL be supported longer, firmware and driver wise..a few years down the road you may not be able to get drivers for a new OS version, Lsilogic drivers have always been compatible with the perc add-in cards, and they support them for many years, providing new drivers for new OSs quickly.

"and 1 is used for parity"
To be totally correct, the is no dedicated parity drive in any raid 5 array, parity is divided equally over all drives in a raid 5 array.. there are seldomly used raid types which have dedicated parity drives.

"5. For a tape drive, assuming I need to backup 150 GB, can you recommend a good tape drive that doesn't cost a fortune?"
Any decent drive is not cheap. If you get a cheap low capacity, slow drive, you will need to have multi tape backup. Cheap drives will wear out much faster..If a inexpensive drive takes 8 hours to backup, and an expensive drive such as an AIT 3 takes 1 hour, how long is the less expensive drive going to last, with 7 extra hours of use per backup? Basically with TBUs, you get what you pay for.


........................................
Chernobyl disaster..a must see pictorial

http://www.kiddofspeed.com/default.htm

 

[SirBC]

I didn't know that it was standard to divide the drives of a mulit-RAID setup over both of the channels. Admittedly, I know nothing about RAID configurations but for some reason that seems counterintuitive. What would be the downside of keeping the RAID 1 array on one channel and RAID 5 on another?

Thanks for all the info guys! I’m going to order the server this week, so hopefully I should have it soon.

- Dave

 

[technome]

In your case it is not a major issue, as it is more important with a greater number of drives than you presently have; there would be slightly more scsi bus contention on the raid 5 channel due to the greater number of drives, than if the drives were evenly distributed over both channels; for it to affect the server, you would need to have a serious load on it.

The 2800 was database benchmarked in a review, it ranked with more expensive servers. Solid, heavy server, fans are a bit noisy, but better to have sufficient cooling than lower noise levels.

Setup a command line consistency check weekly, if off hours have slow periods. Once a month is not enough, as recommended by Dell. Consistency checks find and mark bad blocks before they can build up.

setup a command line disk cleanup nightly, set before the backup.

Setup up a scheduled nightly defrag again scheduled before the backup window.

Should the server be slow on intial setup, go into the network connection, and turn "flow control" off in the Intel NIC properties.

Lastly, look into Executive Software's "Undelete", beats "system restore" for up to the minute file recovery..I consider this a must have on production servers.


........................................
Chernobyl disaster..a must see pictorial

http://www.kiddofspeed.com/default.htm

 

[SirBC]

Good stuff. Thanks!

 

[SirBC]

BTW, would you have any recommendations on how to partition the drives?

SBS2003 premium with ISA, light Exchange use, mainly using a SQL based practice management program (dental office). About 10-15 users concurrently connected to the database. The practice management software tracks patient location in the office so it's constantly updating the screens of any user who is connected. So, even if the user is doing nothing (ie, sipping coffee), it is querying the database. The other component of the software is digital imaging/X-Ray's for each patient (approx 2 GB/year total). I’m not entirely sure if the software stores the photos in the database or not, but I don’t think it does.

I was thinking:

RAID 1 – 36 GB
C:\ OS – 36 GB

RAID 5 – 72 GB
D:\ Programs – 8 GB
E:\ Exchange - ? GB
F:\ Data - ? GB
G:\ SQL – Remaining of 64 GB

 

[technome]

Don't have too much experience with SBS but...

Probably better off installing all of SBS on the C: partition Exchange,ISA etc. If you worried about space on the C: drive, I would create a program directory on the raid 5, and install all software other than SBS OS to sub directories of apps, 95% of programs will run happily in directories other than c:\program files. Redirect data from SQL, exchange etc to a sub directory of the raid 5.

I would create 1 partition on the raid 5, use sub directories to separate data. Using multiple paritions only complicates things eg, if you eventually need more room on a particular partition, what will you do.

Hope your getting at least 2 gig ram, 15k rpm drives should help with the SQL based programs, 10k is sufficent though

Medical office, get a decent TBU, loss of any info could be a big liability. If the office has the money, get a auto loader..load the tapes weekly or even monthly. Differential backs during the week days, full on the weekend

........................................
Chernobyl disaster..a must see pictorial

http://www.kiddofspeed.com/default.htm

 

[twwabw]

Be aware, that by default, when Dell setup runs on a new server, the OS partition will be set to 12Gb. This is not a problem per-se, but you need to be aware of it. If you require more space on you OS partition, then you'll have to load SBS from scratch. Not a crisis- use the Dell Server assistant CD to run the initial setup which will load the correct Raid drivers into the setup answer file, and partition the drive(s) as you dictate.

A couple other points- you mention SBS and SQL- remember, if your app requires full-blown SQL server, you'll need to purchase the Premium version of SBS- not the standard version. If your app runs on MSDE- then no matter. Also, you have some unique requirements since this is a medical office- namely HIPPA, which is the acronym for the Health Insurance Portability and Accountability Act of 1996. Do some research if you've never dealt with it before. It's a different world. When you mention Medial Office and e-mail in the same breath.... be cautious. For instance, your backup strategy needs to be defined, and documented, and secured. Remember to encrypt those backups!! And that's just the tip of the iceberg.

Personally, if I were running an SBS box with Exchange AND a heavily used SQL app, I would consider even more than 2 Gb of memory.

 

[NickFerrar]

Hmm yeah I didn't realise you can divide disks in one array over the two channels in a split-backplane, that gives a bit more flexibility for sure.

 

[technome]

Nick...
Have not seen you in a while over at the Minasi site.


........................................
Chernobyl disaster..a must see pictorial

http://www.kiddofspeed.com/default.htm

 

[SirBC]

twwabw, I am ordering the Dell without an OS and will be installing SBS2003 Premium myself, so I will be able to partition as needed.

Thanks for the HIPPA info. I'll investigate further.

I'm going to start out at 2GB memory because my office is starting from scratch and will be slow at first. As I get busier I will add ram as needed though.