raid 0 vs raid 0 + 1 whch is better.

[seemychess]

never used raid before so just asking which is best for chess.

[Gian-Carlo Pascutto]

Neither is very interesting for chess. The only time disk matters is for tablebase access, and neither raid gives much advantage there.

Note that raid0+1 prevents you from losing data in case a disk fails at the cost of half the drives.

But for chess it's completely irrelevant.

[Dr.Wael Deeb]

Neither is very interesting for chess. The only time disk matters is for tablebase access, and neither raid gives much advantage there.

Note that raid0+1 prevents you from losing data in case a disk fails at the cost of half the drives.

But for chess it's completely irrelevant.

Totaly agreed here and that's why I'd never given extra money to build raid systems....

[Spock]

Depends on how many drives - RAID 0 does give faster tablebase access, but you are way better off just using 5-men on a fast 8GB flash drive.

[bob]

never used raid before so just asking which is best for chess.

raid 0 (striping). But only if you have good I/O (SCSI devices primarily).

[bob]

Neither is very interesting for chess. The only time disk matters is for tablebase access, and neither raid gives much advantage there.

Note that raid0+1 prevents you from losing data in case a disk fails at the cost of half the drives.

But for chess it's completely irrelevant.

Raid 0 is far faster, because you can do parallel reads to read in one chunk of an EGTB file. This is how I use them on my office box. When Eugene and I first started testing blocksizes for compression, there were several things we considered, and testing on raid 0 was one of them and with good SCSI controllers, it was a big win.

[Gian-Carlo Pascutto]

Raid 0 is far faster, because you can do parallel reads to read in one chunk of an EGTB file. This is how I use them on my office box. When Eugene and I first started testing blocksizes for compression, there were several things we considered, and testing on raid 0 was one of them and with good SCSI controllers, it was a big win.

Is it really the block read time that limits things? I'd expect it to be the access latency by far. I don't see how access latency would improve from RAID-0.

Perhaps it's less if you have 15000 rpm SCSI drives.

Edit: One thing that WOULD improve is engine startup time. It can be a pain with 6-men...for that both RAID-0 and RAID0+1 would indeed be faster.

[bob]

Raid 0 is far faster, because you can do parallel reads to read in one chunk of an EGTB file. This is how I use them on my office box. When Eugene and I first started testing blocksizes for compression, there were several things we considered, and testing on raid 0 was one of them and with good SCSI controllers, it was a big win.

Is it really the block read time that limits things? I'd expect it to be the access latency by far. I don't see how access latency would improve from RAID-0.

Perhaps it's less if you have 15000 rpm SCSI drives.

Edit: One thing that WOULD improve is engine startup time. It can be a pain with 6-men...for that both RAID-0 and RAID0+1 would indeed be faster.

raid-0 is blindingly fast for that as well. But when you start reading big blocks of compressed data, bandwidth becomes an issue as well. When I can set it up again, I can run a test using a single 15K scsi drive, and then a raid-0 set of the same drives. When I tested this last, it made a significant difference. Latency is an issue, particularly on the slower drives. But bandwidth is right in there as well. The other advantage is that the average seek distance is about 1/4 of what it is on one drive, when you use 4 drives with raid-0 so it also drives down the seek-time as well... I've tried it on SATA drives and they suck at this so there is not much of an advantage there other than a little savings on seek time, and a tad of help on latency since an RPS controller can choose which stripe of the data to read first to optimize the multiple latencies across the drives.

[M ANSARI]

Well RAID 0 on SATA II SSD drives (especially the latest ones) is the best of both worlds. Excellent latency with good bandwidth.

RAID 0 is usually designed for an application where speed is critical. Say if you have 2 drives in RAID 0 and you lose one ... then all you data is gone.

RAID 1 is usually designed for an application where data integrity is critical. So if you have 2 drives in RAID 1 and you lose one ... you can rebuild your data by simply installing a new drive. Basically it mirrors the data on both drives which also give you half the amount of available data storage. You do get better performance than a single drive due to the data being placed in 2 locations instead of one but not as high performance as RAID 0.

Obviously you are not confined to 2 drives in a raid array and big raid arrays can easily be the most expensive item in a system.

[bob]

Well RAID 0 on SATA II SSD drives (especially the latest ones) is the best of both worlds. Excellent latency with good bandwidth.

RAID 0 is usually designed for an application where speed is critical. Say if you have 2 drives in RAID 0 and you lose one ... then all you data is gone.

RAID 1 is usually designed for an application where data integrity is critical. So if you have 2 drives in RAID 1 and you lose one ... you can rebuild your data by simply installing a new drive. Basically it mirrors the data on both drives which also give you half the amount of available data storage. You do get better performance than a single drive due to the data being placed in 2 locations instead of one but not as high performance as RAID 0.

Obviously you are not confined to 2 drives in a raid array and big raid arrays can easily be the most expensive item in a system.

I don't see how you get any better performance at all on raid-1. You have a primary drive and a secondary (mirror) drive. How is the second drive going to help the speed of accessing data from the primary drive?

One can also use raid-5 and get both a speed boost because of the striping, plus reliability because of the redundant data written on one drive. But it isn't as fast as raid-0 for egtbs and I don't care about reliability as I will just copy them back after replacing the drive anyway, the data is not critical because it can be restored.