No Battery on Raid controller warning when selecting Write---> Thru??

[pmedia]

I have been working on a new Raid 5 server for a while and today i got a fair transfer rate for the first time(i can write to the server at 70-80mbps)

I have created 1 array with 7x750GB's and 1 750Gb hot spare.

then i created 2X 2TB logical disks and in Win xp i have created 2 "simple" volumes F: and G: based on the logical disks this works, but my initial plan was to have 1 large volume but I'm not sure if using the spanned or stripe option in winxp disk management will destroy the raid5 volume and the parity "security" in raid 5?

another thing: It was in the Intel web console that I used these settings to get fast write:

Read---> No Read Ahead
Write---> (changed it from 'Thru' to 'Back' and then the speed improved)
I/O---> Direct

when i changed the Write setting i got an alert:
"Battery Absent. Improper shutdown or powerfail will result in loss of data with Write Back mode."

So i guess my setup will be bad no matter what i do

I have bought an UPS so isn't that helping or am i taking a big risk by changing 'Thru' to 'Back' with no battery?

 

[PurduEE]

I have been working on a new Raid 5 server for a while and today i got a fair transfer rate for the first time(i can write to the server at 70-80mbps)

I have created 1 array with 7x750GB's and 1 750Gb hot spare.

then i created 2X 2TB logical disks and in Win xp i have created 2 "simple" volumes F: and G: based on the logical disks this works, but my initial plan was to have 1 large volume but I'm not sure if using the spanned or stripe option in winxp disk management will destroy the raid5 volume and the parity "security" in raid 5?

another thing: It was in the Intel web console that I used these settings to get fast write:

Read---> No Read Ahead
Write---> (changed it from 'Thru' to 'Back' and then the speed improved)
I/O---> Direct

when i changed the Write setting i got an alert:
"Battery Absent. Improper shutdown or powerfail will result in loss of data with Write Back mode."

So i guess my setup will be bad no matter what i do

I have bought an UPS so isn't that helping or am i taking a big risk by changing 'Thru' to 'Back' with no battery?

In write-through mode, changes to the data on the hard drives are written to the drives 'thru' the cache. There is not a situation wherein the data in the cache and the data on the drives are not the same.

In write-back mode, changes to the data on the hard drives are written to the cache and eventually synched back to the physical drive. This cuts down the number of writes to the physical media, since it only writes 'back' to the drives when the cache space is needed by different data. (this is a really simplistic explanation). However, if there is a system crash, for instance, where the card loses power (as in a PCI reset), the cache will be lost and any changes that should have been written to the drives will not be made. Data is lost and files get corrupted. A UPS won't protect you from this possibility, since the machine doesn't need to lose AC power for this to happen.

Batteries for RAID controllers usually aren't more than $100 or so. You should either get a battery or use write-thru, especially if you're dependent on this data (since you're running in RAID 5, I assume it's important stuff). Who makes the card you've got?

 

[pmedia]

In write-through mode, changes to the data on the hard drives are written to the drives 'thru' the cache. There is not a situation wherein the data in the cache and the data on the drives are not the same.

In write-back mode, changes to the data on the hard drives are written to the cache and eventually synched back to the physical drive. This cuts down the number of writes to the physical media, since it only writes 'back' to the drives when the cache space is needed by different data. (this is a really simplistic explanation). However, if there is a system crash, for instance, where the card loses power (as in a PCI reset), the cache will be lost and any changes that should have been written to the drives will not be made. Data is lost and files get corrupted. A UPS won't protect you from this possibility, since the machine doesn't need to lose AC power for this to happen.

Batteries for RAID controllers usually aren't more than $100 or so. You should either get a battery or use write-thru, especially if you're dependent on this data (since you're running in RAID 5, I assume it's important stuff). Who makes the card you've got?

Thank you for the explanation i understand what you're saying, I were really frustrated before i found that write back option since the speed were so slow that this new expensive server seemed useless but i understand that there's a data security issue with that setting.

the raid card is Intel srcs28x and I'm trying to find a battery but I'm not sure if it's available, is this a battery like the small one for the motherboard bios?

 

[pmedia]

Thank you for the explanation i understand what you're saying, I were really frustrated before i found that write back option since the speed were so slow that this new expensive server seemed useless but i understand that there's a data security issue with that setting.

the raid card is Intel srcs28x and I'm trying to find a battery but I'm not sure if it's available, is this a battery like the small one for the motherboard bios?

I just found some info on the battery module in the hardware manual, i'll look into this

I did try to change these options:

Read---> No Read Ahead
Write---> (changed it from 'Thru' to 'Back' and then the speed improved)
I/O---> Direct


to:

Read---> Read Ahead
Write---> Thru
I/O---> Cached

but it didn't give any speed increase over No Read Ahead/Direct so i guess I'll try to dig up that battery module.

 

[PurduEE]

Thank you for the explanation i understand what you're saying, I were really frustrated before i found that write back option since the speed were so slow that this new expensive server seemed useless but i understand that there's a data security issue with that setting.

the raid card is Intel srcs28x and I'm trying to find a battery but I'm not sure if it's available, is this a battery like the small one for the motherboard bios?

It's not as small as a cr2032 or anything like that. It's more the size of a cordless phone battery - it's also rechargeable, unlike motheboard batteries.

A quick froogle shows your battery in stock at a bunch of places. I'm not familiar with most of them, so some checking on resellerratings.com may be in order. Here's the cheapest at ~ $135:

http://www.2020pc.com/ssproduct.asp?pf_id=10506558

There's a lot of choices between $135 and $150. The part number is AXXRIBBU1.