Enable write behind caching?

[John]

If you run a SCSI HDD, do you need to check this option in the system properties > file system properties > removable disk tab?

 

[Lore]

Usually, yes. I believe it allows faster transfers between devices.

 

[skemlawn]

Yes it is faster however if the power goes out, or your computer gets unplugged, or if it crashes during a write to the hdd it could potentially really screw stuff up. What it does is cache the data to be written, then writes it.

I found that adaptec has a good knowledge base that you could use. As a matter of fact I think I'll do that now, because I have a bunch of scsi goods.

 

[skemlawn]

alright wait a sec. I should have read more carefully your post before I posted. That check box is ONLY for removeable scsi storage devices. I.E. Zip, Orb, tape and what not (but probably not Cd-r's). You won't see any increase speed, unless you use removable scsi storage

 

[skemlawn]

From the adaptec knowledge base:

hat is the purpose of the 'Enable Write Back Cache' switch in SCSI Select? (Article Number000515-0009)
 
Description:
What does enabling Write Back Cache do? What if the device does not support Write Back Caching?
This information applies to the following product(s):
- 19160, 29160N, 29160, 39160 - PCI SCSI Card(s)
This information applies to the following Operating System(s):
- All / PC
 
Solution:
This feature overrides the SCSI devices built in Write Back Caching setting. If this switch is enabled, then the SCSI card will send a command to the device to enable write back caching (even if the default setting for the device is disabled).

If the device supports write back caching, then the command from the SCSI card will override any setting on the device itself. If the device does not support write back caching, then the it will ignore the command from the SCSI card. The default "No Change" (N/C) setting on the SCSI card allows the device to use its default setting for write back caching. Hard drives are the only devices on the market at this time that support write back caching - CDs, tape drives, removeable drives, and scanners do not support this feature.

Enabling write back caching increases performance (since writes are cached to cache RAM on the hard drive just like reads) but increases the risk of losing your data. Unwritten data in cache RAM is lost if and when the power goes out. This option should only be enabled if your system is protected by a UPS (Universal Power Supply) that will allow your system to go through a proper shut down sequence on the power of a battery even if the main power goes out. When the system properly shuts down the information from cache RAM is saved magnetically to the disk (and therefore is not reliant on power to retain the information). The risk of data loss is not worth the performance enhancement if your system is not protected by a UPS.





And another one:

Description:
What are the risks and benefits of drive write-back caching?
This information applies to the following product(s):
- AAA-UDMA - PCI RAID Card
This information applies to the following Operating System(s):
- Windows NT 4.0
- Windows 2000
- Novell 4.11
- Novell 4.2
- Novell 5.0
 
Solution:
Most disk drives allow write-back caching which greatly speeds up writes to the disk. This feature enables an application program to continue executing once write data is successfully sent to a drives internal cache. In very rare cases a deferred write error can occur (for example, a parity error within the drive's cache). A deferred write error means data has been incorrectly written and is no longer available to the I/O system. The error is unrecoverable. The consequence of turning off the write cache on the drive is slower write performance but deferred write errors are prevented.

 

[TechMaster]

I have this option for my Maxtor D-MAX Plus 20.4GB in Windows 2000 - Should I keep it enabled (I understand the risks but I don't know if they actually worth it...)

 

[Goi]

Write behind caching basically means data that is sent to be written to your drive media won't get written immediately. Instead, it will be written first to a cache memory(presumably system memory), and then later on be written in larger chunks to the drive media. The idea is that this will be faster and more efficient since you won't be writing small chunks of data to the slow drive media all the time.

However, in sensitive operations like streaming media and CD burning, its safer to disable write behind caching because if you do multiple disk accesses at the same time, data might intefere with one another and there's no gaurantee that data that is supposed to be written will in fact be written. Also, in the case of a power outage, you will risk losing some data.

Since you mention the checkbox in the removable disk tab...it shouldn't matter to your SCSI HDD, unless you somehow have an external SCSI HDD, or have checked the "removable" box in your HDD properties. OTOH, in the "Troubleshooting" tab in file system properties, there is also a checkbox marked "Disable write-behind caching for all drives", which affects all drives, removable or not. If you're usually multitasking with sensitive data and operations, you might want to check that box for added safety. For all other uses, it should be fine to leave it unchecked for that extra speed.