Mark's Blog

Last weekend I’ve been evaluating my work on qKAI and thus worked extensively with datasets of about 30 GB in MySQL, with DBPedia dumps. To speed up file read I’ve added my spare fourth Western Digital WD6400AAKS to Adaptec 3805 RAID and:

1. done online RAID level migration from RAID 5 with three HDD to RAID 10 to four HDD,
   in the hope writing performance will increas as suggested by this article
2. ran ATTO disk benchmark on the new array
3. been unsatisfied, and (again) converted the RAID 10 to a four-drive RAID 5
4. now been puzzled about Windows Server showing free areas strangely
   and not letting me expand the primary partition the volume’s new size

Conversions took Read more »

Tags: RAID, Windows Server 2008

Some time ago I blogged about Windows Server 2008 Software RAID performance and learned that software RAID 5 is unusable at workstations. While opening large files and/or working with them the system became unresponsive. Wondering where the bus congestion might occur I’ve done some research and like to share the math with you for a better insight. Jump to the end for my conclusions and usage scenarios! Read more »

Tags: RAID, Windows Server 2008

Last Saturday my RAID card has arrived. Saving the old system installation (with VMs) was a charm using WS2K8’s backup feature. About half an hour later I’ve put in the new controller, attached three WD6400AAKS an run RAID5 array creation via the card’s firmware menu. (version was 5.2 15728)

Restoring has been trivial. Starting from a Server 2008 DVD (Vista DVD works, too) you can select “full system restore” and have the backup expanded on the new volume (1.2TB, BTW). During building the RAID5 it was done with about 50MB/s. Here’s a video for you to get an idea what it was like.

Thanks to RAID level migration you can also start with a RAID1 (mirroring) at 2 HDDs, then upgrade to a third hard drive and switch to RAID5 in the background. Finally, adding a fourth one you can expand volume size – online! WS2K8 can expand your partitions online, too. Great!

Upgrading to latest BIOS (15753) is done by the storage manager. Windows already ships with old but functioning drivers, therefore booting works without hassle. For Linux, there are such drivers in the kernel. By the way, Adaptec has a linux blog, and here are is another RAID SAS card review.

With three HDDs in RAID5, I have on average 200MB/s read and 100MB/s write performance. Staggered drive spin-up is supported by Western Digital HDDs but not Seagate 7002.11 and 7200.10 (even not by SATA pins etc.) – so watch out buying drives.

Tags: RAID

Unfortunately, the congestion described earlier can occur with every other software RAID. It might be no problem with dedicated file servers, but for my server’s dual use as workstation it is a no go.
Interestingly, I’ve found very few reviews explicitely naming the CPU usage of RAID controllers and giving the performance of one HDD for comparisonof read/write penalty. That must change!

A cheap dedicated RAID card I’ve considered buying was Highpoint’s RocketRaid 2310 (which is identical to 2300 except for PCIe x4 bus for more than 250MB/s). But it turned out to be “hardware assisted software RAID“, a very well implemented one indeed. Neverthless unusable for RAID 5. [Review at Techgage]

So, after reading reviews about PCIe RAID controllers I’ve decided to buy an Adaptec 3405 RAID controller (identical to Adaptec 3805 except for having one SAS connector, not two; both with Intel’s IOP at 500Mhz and 128 MB RAM) to get the best of the bargain. [Review; compare with one bare HDD they used.] By the way, it consumes only 3.3 W.

Conclusion of my RAID odyssey: Either it is time or money. For RAID, let it rather be the latter.

Tags: RAID