T7k250 160G x4 @ Raid 0+1

[a843433]

做個簡單的測試, 作業系統是RedHat Fedora Core 4; 主機板是tyan 2895; 兩顆AMD OP 248; 介面卡是Adaptec 2230SLP, 128M cache; 硬碟為Seagate 36G 一萬五千轉 8MB U320:


先來看看, 四顆一萬五千轉硬碟, 利用其中三顆硬碟RAID 5, 另外一顆建立成HOT SPARE的數據.

# hdparm -Tt /dev/sda

/dev/sda:
 Timing cached reads:  3248 MB in 2.00 seconds = 1623.44 MB/sec
HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl for device
 Timing buffered disk reads: 156 MB in 3.01 seconds = 51.90 MB/sec
HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl for device

如果只有單一顆硬碟, 沒有RAID時:

# hdparm -Tt /dev/sda

/dev/sda:
 Timing cached reads:  3928 MB in 2.00 seconds = 1964.00 MB/sec
HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl for device
 Timing buffered disk reads: 165 MB in 3.01 seconds = 54.81 MB/sec
HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl for device

可以看到, RAID 5模式下, 硬碟讀取效能的確會受到影響.

如果, 把HOT SPARE拿掉, 還是RAID 5的情況底下:

# hdparm -Tt /dev/sda

/dev/sda:
 Timing cached reads:  3404 MB in 2.00 seconds = 1702.3 MB/sec
HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl for device
 Timing buffered disk reads: 159 MB in 3.01 seconds = 52.82 MB/sec
HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl for device

可以看到, 效能多少會受到影響.
(以上, 每一個數據, 都是系統重新安裝之後所得; 介面卡本身的參數都是預設值不做調整, 韌體版本為8200)



至於, 對照組:

下面, 是單顆WD SATA 一萬轉 36G, 使用onboard Nvidia晶片所得到的資料.

# hdparm -Tt /dev/sdb

/dev/sdb:
 Timing cached reads:  3252 MB in 2.00 seconds = 1625.43 MB/sec
HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl for device
 Timing buffered disk reads: 188 MB in 3.01 seconds = 62.41 MB/sec
HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl for device

至於 can 網友所說的:

Originally posted by can
用 10 個以上的硬碟做陣列會是不明智的行為嗎？
RAID 卡掛了就換卡、主機板死了就換主機板、顯示卡不動了就換顯示卡、PSU 發春就換 PSU（奇怪， RAID 都用得起，怎麼用的不是 Redundant Power Supply？）
怎麼可能壞一個東西馬上工作就不能做呢？

你說的, 可能是個人系統, 那才有可能這樣子弄, 畢竟個人系統用的主機板取得比較容易; 我說的, 是堆在機架上, 那些4U 5U的機器. 一來, 主機板取得困難, 二來, 你就算想單買, 廠商也不見得會賣你. 就算有了主機板, 你能否裝上去都是個問題. 在大部分的情況下, 多買一張價值兩三萬的主機板供奉在那邊是否有價值.........?

會使用到超過五顆以上硬碟的陣列, 應該, 不是普通人吧?